The Vegetation of Falcn State, VenezuelaAuthor(s): Silvia MatteucciSource: Vegetatio, Vol. 70, No. 2 (Jun. 15, 1987), pp. 67-91Published by: SpringerStable URL: http://www.jstor.org/stable/20038134Accessed: 10/03/2009 15:38

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Vegetatio 70: 67-91, 1987 ? Dr W. Junk Publishers, Dordrecht

- Printed in the Netherlands 67

The vegetation of Falcon State, Venezuela*

Silvia Matteucci**

Departamento de Producci?n Vegetal, Universidad Nacional Experimental Francisco de Miranda, Apar tado 7434, Coro, Falc?n, Venezuela 4101

Keywords: Classification, Formation-series, Dominance-type, Physiognomy, Venezuela

Abstract

A semi-detailed first approximation study of the vegetation of an heterogeneous area, located in the Caribbe an region is presented. Field information on vegetation structure and function, flora and environmental fac tors was collected in a systematic way in order to reduce subjective decisions as much as possible. Indepen dent physiognomic and floristic classifications were developed through the analysis of field data. The

physiognomic classification is artificial, easy to understand by a wide variety of users. It facilitates the iden tification and description of land units, as well as the monitoring of vegetation changes. The floristic classifi

cation, based on dominance-types, was obtained from tabular comparison. The relationship between both classifications is analyzed. In order to disclose the temporal and spacial relationships among vegetation units, and to allow for extraregional comparisons, the results were translated into Beard's formation series. The relations between the physiognomy- and dominance-types and the formations are analyzed. The vegetation is described in terms of Beard's formations. The relationships between vegetation pattern and environment are discussed. The results are compared to those of previous studies.

Introduction

Although the vegetation of the parts of the Carib bean region has been described (e.g., Asprey & Robbins, 1953; Beard, 1949; Howard, 1973; Stoffers, 1956), little has been reported on the Caribbean vegetation of northern Venezuela. This

paper is the first attempt to produce a comprehen sive semi-detailed study of the vegetation of Falcon State. Other studies have been done for specific land use purposes (O.T.E.E., 1958) or in larger regions that include Falcon State (Hueck, 1960;

M.A.C., 1961; Pittier, 1920; Smith et al, 1973; Tamayo, 1958). However, these accounts are of a general nature and the vegetation types are only vaguely described. Most of the studies rely on aeri al photographs with very little field checking. Fre

quently, the biogeographical map of Venezuela by Ewel & Madriz (1968) is used for the characteriza tion of the local vegetation. However, this is a cli

matic map and the communities described within the life zones of Falcon State coincide neither with the actual nor with the potential vegetation, in

most cases.

The present account is based on a systematic field study of the vegetation and flora as part of a

* Nomenclature of species follows Matteucci et al. (1979a, avail able on request). Voucher specimens have been deposited in the National Herbarium (VEN), in the Central University Herbari um (MY) and in the reference collection of the Instituto Tec nol?gico de Coro, Falc?n.

** I am deeply indebted to A. Colma and L. Pia, who partici pated actively in the project at all stages. I am very grateful to Dr D. Billings for his comments on the manuscript, and to the

editorial secretariat for helpful improvements of the text. Field work was supported by the Venezuelan National Research Council (CONICIT).

68

regional survey (Matteucci et ai, 1985) which was to provide the baseline information for research and development planning. Simple physiognomic and floristic classifications were developed, that

would be easily understood by non-specialists. These allow the systematic collection of informa tion and the identification and definition of land

units.

These classifications were obtained independent ly and combined in order to provide a description of the present vegetation (Matteucci et al., 1979a). However, in order to obtain a temporal and spatial interpretation of the community distribution, and to allow for extraregional comparisons, the results

were analyzed in terms of Beard's formation-series

system (Beard, 1944, 1955). In dry climates, differ ences in topography, exposure and soils, as well as

rainfall seasonality have greater influence on vege tation pattern than mean annual precipitation.

Beard's approach takes into account this fact in

relating physiognomy to environmental features. It

also provides a means for detecting successional re

lations, and it is applicable to local situations. The natural vegetation has almost entirely disap

peared in Falcon. It is likely that most of the pres ent closed forests and woodlands represent late

stages of secondary succession. Different stable

communities may have replaced the natural vegeta tion types, due to the fact that changes in habitat

may be faster than vegetation recovery in a tropical area with the topographic and climatic conditions

prevailing in Falcon. Even though it is likely that

climax communities do not exist here, it is possible to detect apparently stable, integrated, mature com

munities, which comply with Beard's definition of

climax (Beard, 1944). However the lack of eco physiological knowledge of local species and of

historical facts about land occupation renders the

interpretation difficult (Van Steenis, 1961). This paper also aims at presenting a method to

study and interpret the vegetation of an extensive

heterogeneous region at a first approximation.

The study area

Falcon State borders the Caribbean Sea. It com

prises 24750 sq. km of land with extreme varia tions in relief, topography and history of human

occupation. There are five physiographic provinces: Coastal Plains, Coastal Piedmont, Falcon Ranges, Central Valleys and Eastern Maritime Valleys.

Details of geology, geomorphology and soils have been published elsewhere (Matteucci et ai, 1979b; Colma & Matteucci, 1982). In the Creta ceous, the area was occupied by a g?osynclinal belt

stretching in a ENE-WSW direction, covered by a continental sea. Several episodes of continental and

marine deposition produced interbedded shale and

sandstone, with layers of conglomerate and lime stone. Orogenetic activity started in the Lower Mio

cene, with the uplifting and tilting of the Coastal

Piedmont, and ended in the Pliocene. The deposi tional plains are overlain by Quaternary deposits,

with Tertiary sediments exposed on the erosional landforms.

The Coastal Plains comprise the Paraguan? Pen?nsula, the isthmus and the coastal fringe to the west. The relief is low, with extensive floodplains, except in the central portion of the mainland, which is raised and denuded, with exposed stony surfaces. The highest altitude (815 m altitude) is found on an isolated hill in the Peninsula. The

shore, formed by recent sand deposits, consists of

sandy beaches with areas of dunes. The rivers are

intermittent, and carry flashfloods with suspended sediments in the rainy season. In most of the prov ince the soils are medium- to fine-textured, of the

suborders Orthids, Argids, and Orthents (Calcic Xerosols, Yermosols, and Lithosols). The soils on the coastal fringe and isthmus belong to the subor der Psamments (Eutric Regosols).

The Coastal Piedmont constitutes a belt of tran

sitional topographic relief, with erosional and

depositional landforms, located between the Coast al Plains and the Falcon Ranges. It varies in eleva

tion from 100 to 400 m towards its southern border, and consists of a succession of hogbacks and dis

sected low ridges. The soils are shallow and lithic

(Lithosols), except in the few valleys and depres sions, where the suborder Orthids (Haplic and Luv ic Xerosols) predominates.

The Falcon Ranges Province occupies 44 ?/o of the State and comprises three ENE-WSW oriented

parallel ridges separated by wide valleys. The northern and middle ridges are divided into three

main mountain-masses by gorges and valleys along which some rivers flow northwards. The slopes are

steep (25-50 %) and the relief is drastic, with knife-edge divides and v-shaped ravines. The alti tude ranges from 200 to 1500 m. To the east,

mountain remnants are found within the Eastern Maritime Valleys. On the top of these, as well as on

the easterly mountain-mass of the northerly ridge, karst landscapes formed by calcareous masses of

up to 350 m of exposed limestone have developed. The soils are heterogeneous: mostly Orthids and Orthents (Calcic Xerosols and Lithosols) on the slopes; thick organic Rendolls (Rendzinas) on the

mountain summits, and Tropepts and Orthids (Eu tric Cambisols and Haplic Yermosols) in the val leys.

The Central Valleys Province encompasses the syncline valleys between the mountain ranges.

Topographic relief is low and mostly flat or un

dulating, except for some low foothills and elongat ed, narrow buttes. The soils, shallow and covered by gravel, belong to the suborder Orthents (Calcic Xerosols and Lithosols). In the valleys and dried up water courses, the soils are fine-textured and overlain by gypsiferous salt deposits, of the subord ers Fluvent and Orthids (Fluvisols and Gypsic

Xerosols). The Eastern Maritime Valleys comprise the ba

sins of the four main rivers that flow to the east and north from the Falcon Ranges. The basins are bor dered by low divides formed by undulating high plains or mountain remnants. The altitude ranges

from 300 m next to the foothills to 0 m at the shoreline. Slopes are gentle and near the coast the plains become temporarily or permanently flood ed. Soils form a mosaic of patches of Usterts and

Argids (Chromic Vertisols and Luvic Yermosols) on the hills and undulating plains, with fine-textured

clayey and saline patches of Orthids and Aquents (Haplic Yermosols and Eutric Gleysols) on the northerly valleys, whereas in the southern portion, Tropepts, Fluvents, and Aquents (Eutric Fluvisols and Gleysols) occupy the river margins, and Ustalfs and Usterts (Dystic Nitosols and Ferric Luvisols) predominate elsewhere.

69

The coastal plains, subjected to surface trade winds, show a climatic anomaly. At this latitude, in such a maritime location, abundant precipitation

would be expected. However, limited and erratic rainfall prevails. The possible cause of this anomaly is the stress that arises from the interaction between

topography and the cool Caribbean Sea, which forces the air masses to diverge and subside over the

dry area (Lahey, 1973). On the mountain ranges orographie rainfall occurs with rainshadows on the lee sides. The summits are subjected to frequent cloud cover. Rain is also less sparse in those valleys

which open to the east-north-east.

Rainfall comes as heavy showers of short dura tion. Rainfall seasonality characterizes the area. A detailed analysis of local climatic data has shown that the ratio of potential ?vapotranspiration to

temperature is 3.56 (Matteucci & Colma, 1986). Thus, in order to give a realistic description of the

climate, the diagrams were constructed in such a

way that 10 ?C are made to correspond to 35.6 mm

precipitation (Fig. 1). On the coastal plains and central valleys mean annual precipitation ranges from 142 to 492 mm and is concentrated in a short

,A6UA CLARA?85) 28,7?C 463mm. .TUCACAS (25)

JT 'M'A rM ' J ' J ' A ' S ' 0 ' N ' D J ' F'M' A" M" J " J ' A'S' O'N" D

SOCOPO(520) 24,5?C Il76mmi 16 1 ARAURIMA(35m) 27,6?C 1527mm 1 19

J7'MTA^M' J'J ' A'S 'O'N'D J' F' M'A'M" J '

J'A'S 0 KTD

Fig. 1. Climate-diagrams, with temperature in ?C on the left vertical axis and precipitation in mm on the right one. For ex

planation see text.

70

rainy season (Fig. la). The high ?vapotranspiration rate produces drought all year round. In the Mari time Valleys, the rainy season is longer (two to four

months); mean annual precipitation ranges from 600 to 1700 mm and there are two to nine humid

months. There is a N-S humidity gradient, and the northern fringe is less humid (Fig. lb) than the southern portion (Fig. lc). On the Mountain

Ranges and the southern extremity of the western Coastal Plains there are two rainy seasons and mean annual precipitation ranges from 750 to

1250 mm (Fig. Id). Remarkably uniform high temperatures prevail

throughout the year, though day-night temperature differences may reach up to 14?C. On the Coastal Plains mean annual temperature is 28 ?C to 29 ?C, and it decreases up the mountains with an altither

mic coefficient of 0.57.

Methods

Data collection

The study area was stratified through deductive photointerpre tation. Land segments (0.25 sq. km minimal area) were delineat ed on panchromatic 1:60000 scale photographs, resulting in

556 photo-interpretation units. After field reconnaissance, crop

and pasture land units were discarded and 213 vegetation units

were recognized. Plots were marked on the aerial photographs on a representative site within each unit. In the field, the land

segment was traversed as far as roads permitted to confirm the

site representativeness and check up the limits. After field in

spection of a sample stand of around 0.5 ha, physiognomic and

floristic data as well as information on the environment were

recorded on a check sheet. Random sampling would have been

extremely difficult and time consuming in such an extensive and

heterogeneous region and was not attempted.

The structural features considered were number of layers, mean height of each, maximum and minimum height of the

leafy portion of each synusia, as well as its spacing according to

Fosberg's scale (Table 1). Leaf size, texture and shape were recorded for each synusia.

The species present were listed. Voucher specimens were col

lected when identification in the field was not possible. Growth

form, leaf persistence and phenological stage of each species were recorded. The growth form categories considered were: tall

trees (5 m or taller), low trees (shorter than 5 m), shrubs, forbs, graminoids, lianas, epiphytes, hemi-parasites, column cacti,

shrubby succulents, small succulents, herbaceous climbers, and

tuft plants. Leaf persistence was obtained from repeated obser

vations through the seasons, or from the local literature.

The species cover-abundance was estimated by means of a

modified Braun-Blanquet scale (Table 1). The use of two differ ent scales to assess two different groupings of the same elements

served to check the estimations.

Leaf periodicity at the community level was determined from

the relative abundance of deciduous and evergreen species. This

makes sense because leaf fall of deciduous species is syn chronized at the onset of the dry season. Thorniness was deter

mined in the same way; that is, by the relative abundance of

thorny vs non-thorny species. A profile diagram was constructed for each stand (Fig. 2).

The mean height of each synusia is represented by the horizontal

line, whose length shows the cover degree. The vertical line

depicts the height interval of the leafy portion. Each growth form was identified by a colour and a symbol, to facilitate visual

comparisons. The percent cover for each growth form was ob

tained from the summation of the mean cover degree of the spe cies. The synusia with less than 3 % cover were not included in

the profile, but were listed as present or absent on the right mar

gin. The check sheet included information on soils, relief,

microtopography, hydrology and land use (Matteucci et al., 1985).

Data analysis

Through visual comparison, the profile diagrams were grouped

Table 1. Plant cover intervals.

Growth form Species

Closed: crowns of shoots touch Continuous (6): >75% or overlap Interrupted (5): 50-75%

Open: crowns or shoots do not touch, but Scattered (4): 25-50%

they cover at least 30% of the surface

Sparse: crowns or shoots more than twice Rare (3): 15-25% their diameter apart Very rare (2): 5-15%

Very sparse: the substrate dominates the Sporadic (1): 1- 5%

landscape Present ( + ): < 1%

9H

CENSO 45 MITARE

BDSE

A

s=0 g=+ H = + E=+ P=0 En=0

"I?r?r?i-1-1-1-1-1-1 10 20 30 40 50 60 70 80 90 100

COVER DEGREE (%)

Fig. 2. Profile diagram; A = trees; a = shrubs; SC = column

cacti; L = lianas; sa = shrubby cacti; s = succulents; h = forbs; g = grasses; H = hemi-parasites; P = tuft plants; En = herbaceous climbers; E = epiphytes; BDSE = closed ever

green thorny forest.

in clusters of similar vegetation structure and these were

segregated according to the community function (periodicity and thorniness) to produce a physiognomic hierarchical classifi cation. The definitions of the classes were formulated from the

features shared by the members of each cluster. A key was pre

pared to facilitate future vegetation typification in the field. The

classification was validated by comparison with land photo

graphs or by field checking. An independent floristic classification based on dominant

species (Whittaker, 1978) was developed from the species lists. After each field trip, these were added to a raw table. The domi

nant and co-dominant species were underlined and the columns were arranged to group together all the relev?s that contained

the same dominant species or the same commodal group (Whit taker, 1978). A species was considered dominant when its abso lute coverage was 16 % or over and its relative coverage was over

30 % of that of any of the accompanying species. Two or more

species were considered co-dominant when their relative cover

age did not differ in more than 30 % from each other. Columns and rows were alternatively rearranged several times to show re

leve clusters that would both share dominants and have similar

composition. In some situations it is not possible to. determine

dominance, either because the vegetation is sparse and diverse

(no species cover more than 16 % of the sample plot) or because it is very dense, rich and diverse (there are too many co

dominants). The relev?s conforming to the former situation were assigned to the dominance-type with which they had the

greatest floristic affinity, given by the maximum number of common species and the minimum of single species. The relev?s

corresponding to the rich dense communities were grouped to

gether, since they correspond to the most humid environments

8

7

1 6

I - 4i UJ x

H 2 I

71

and have the genus Eugenia in common. The dominance-types were named after the dominant or the most frequent species in

the cluster.

Data interpretation

Profile diagrams were compared to profile diagrams based on

Beard's (1944, 1955) definitions. Those communities that do not meet with Beard's descriptions correspond to serai stages and

were assigned to the formations and associations to which they

appear to be related, on the basis of floristic and physiognomic

elements, environmental factors and geography, and applying the concept of potential natural vegetation (Mueller-Dombois &

Ellenberg, 1974). The life form spectra for the formations were calculated from

the relative percent cover of each growth form.

Environmental features were taken into account to assign the

stands to the formations.

Results: Classification systems

The physiognomic classification

The first order of classification comprises the pri mary structural groups, characterized by the domi nant growth form, which determines the vertical structure. These are segregated into structural

groups (the second level) according to the canopy percent cover. The third level corresponds to the

physiognomy-type, which includes consideration of the community function (Fig. 3). Five primary structural groups, 18 structural groups and

47 physiognomy-types have been distinguished in Falcon State.

Forests and woodlands comprise the communi ties dominated by trees (Fig. 4); however, in the forests there is at least one tree layer > 5 m high, and one or two lower layers. In the woodlands,

average height of trees is

72

Fig. 3. Physiognomie classification system. The physiognomy

types are depicted by capital letters as follows: the first letter

corresponds to the vertical structure: B = forest; M = woodland;

C = cardonal; A = shrubland; VH = herbaceous vegetation. The second letter corresponds to the horizontal structure:

D = closed; R = open; Dt = desertic. The third capital letter

refers to the foliage periodicity: S = evergreen; D = deciduous; Sd = mixed. The fourth letter represents the abundance of

thorny structures: E = thorny; I = non-thorny. The superscripts 2 & 3 in the forests refer to the number of tree strata, the absence

of superscript indicates that there is only one tree layer; the low

er case letters following the superscript refers to the height of the

forest canopy: a = canopy higher than 5m;b =

canopy lower

than 5 m.

of the surface; in open communities plant cover of the dominant synusia ranges from 75 to 50 % while in desert vegetation plant cover is less than 50 %

and the substratum dominates the landscape. Sixteen physiognomy-types (34 %) are represent

ed in only a single physiognomic unit each (Fig. 4); they correspond to degraded impoverished commu

nities. In most cases, the presence of floristic or

physiognomic relict elements allows their assign

ment to the more stable community-types.

The forests, which occupy 35.5 % of the State, are scattered everywhere. The two- and three

layered evergreen closed forests are located at an al titude of 200 to 800 m on the hills near the coast

line, up to 1 500 m on the Falcon Ranges Province, and at 20 to 100 m in the southern extremity of the

Maritime Valleys. They are associated with deep or

ganic soils and high mean annual precipitation or

cloud cover. The unilayered forests located on the lower slopes of the mountain ranges and to the south of the Western Coastal Plains are deciduous, open or closed and rather low (5 to 10 m). Those at the eastern extremity of the mountain ranges and in the Maritime Valleys, where climate is subhumid, are higher (8 to 15 m) and denser, deciduous or semideciduous, with noticeable evergreen trees, es

pecially during the dry season. In the arid and semi-arid Coastal Plains, the forests are confined to the river banks.

The woodlands (18.5% of the State) are concen trated in the semi-arid zone, within all the Physio graphic Provinces. The largest extension lies within the Coastal Plains, specially in the Paraguan?

Pen?nsula. Only 7.1 % of the subhumid region is

occupied by woodlands; most of which correspond to disturbed forests.

The shrublands occupy only 7.6 % of the State. The most extensive communities are located in the

Paraguan? Pen?nsula and in the Maritime Valleys. The former are open or desertic xerophytic commu nities dominated by evergreen thorny species. The subhumid zone shrublands, which are deciduous and non-thorny, occupy abandoned pastureland and represent serai stages in a secondary succes

sion.

The 'cardonales' (3 % of the State) occur in the dry zone only. The most extensive communities are

located in the north of the Paraguan? Pen?nsula and on the western alluvial plains; there are small

patches within the Central Depressions. Most of them develop on flat, well drained soils.

The herbaceous community-type occupies a very reduced area (0.24 % of the State) and is scattered in patches on the coastal fringe. It is dominated by forbs with very few grasses, thus they cannot be in cluded in the savannas.

Around 24 % of the study area is occupied by

73

|^75% Pf 50-75?/ i 25-50% [115-25% Kl 5-15% 11-5% fs* :l% 00%

Fig. 4. Growth form spectra of stands representing each of the physiognomy-types. The symbols represent the cover degree of each

growth form. The meaning of letter symbols is given in Fig. 3. The figures in the last row indicate the number of physiognomic units

(each of which may correspond to one or more photo-interpretation units) in each physiognomy-type.

pastureland, either sown or developed after clear

ing with fire. These are man-made savannas, with

predominance of grasses, grazed by cattle and maintained by periodical burning. To the east, in the Maritime Valleys, the savanna constitutes a ma trix within which forest remnants are found.

The floristic classification

The floristic classification includes 15 clusters and 9 outliers. The clusters represent the dominance

types, arranged in a gradient from the humid to the xeric types in Table 2, which shows the woody spe cies composition of each type. The figures cor

respond to the presence percentage of the species in the group. The table does not include all the species recorded, since those present in one or two to three related dominance-types holding less than 50 %

presence in each, were discarded. Thus, of almost 600 woody species recorded, only 144 are listed. In the Eugenia spp dominance-type, 416 woody spe cies were recorded, of which 212 were present only

in this dominance-type and 100 were present in this and related dominance-types. On the other hand, only one species was discarded from each of the Caste la erecta, Prosopis juliflora-Ritterocereus and Ritterocereus spp dominance-types.

There is some overlap in the woody species pres ence and there are groups of dominance-types that differ more with respect to the relative abundance of species than to their presence. This is noticeable

among the most xeric dominance-types; that is, from the Ritterocereus spp dominance-type to the

right in the table. For example, Caesalpinia corlarla has a high presence percentage in these four

clusters, but is dominant only in the C. corlarla

dominance-type; Acacia tortuosa is present in the four types, with varying percentages, but it is never abundant.

None of the species is exclusive to any of the

dominance-types. Only 12 species are not found in the humid types (from the Apoplanesia cryptopeta la dominance-type to the left in the table) and 106 species plus those discarded, are not present in the xeric types. Six species are present in the

74

Table 2. Woody species composition of the dominance-types. The figures depict the presence percentage for each species in each

dominance-type, determined on the basis of the number of stands where the species occurred as a percentage of the number of stands

in the respective dominance-type. The dominance-types are labeled: Pj = Prosopis juliflora; Ce = Castela erecta', Ce = Caesalpinia cori aria; Tb = Tabebuia billbergii; Ch

= Crot?n heliaster; Cp = Cercidium praecox; RR = Ritterocereus spp; AA = Aspidosperma spp; P

R = P. juliflora-Ritterocereus spp; Be = Bourreria cumanensis-Phyllostylon brasiliensis-Bulnesia arb?rea', EE = Eugenia spp; Ac = Apoplanesia cryptopetala; Pd

= Pithecellobium dulce-Capparis hastata; Zp = Zanthoxyllum pterota-Machaerium spp-Eugenia

spp; PP = Pilocarpus spp.

DOMINANCE TYPE SPECIES Haematoxylon brasiletto Castela erecta Cercidium praecox Lippia origanoides 2 izyphus saeri Lye i um nodosum Guaiacum officinale Capparis I i near i s Mimosa arenosa Geoffraea spinosa Cassia biflora Pithecellobium platylobum Diphysa carthagenensis Pereskia guamacho Bursera tomentosa Cissus tri fol i ata Manihot carthaginensis Bur sera karste?iana Jacquinia caracasana Ruprecht i a ramiflora Acacia tortuosa

Caesalpinia cor i aria Ritterocereus spp Prosopis julif lora Capparis odorat issima Pitnecellobium dulce Cissus sieyoides Crot?n heliaster Tabebuia billberqf i Bulnesia arb?rea" Cephalocereus mor itzi anus

Capparis hastata Malpighia spp Bourreria cumanensis Cassia emarginata Bumeli a obt?si fol i a Caesalpinia mo!1 is Rand i a gaumeri Casearia tr?mula

Astron?um graveolens Jacquinia revoluta Tal i si a oliuaeformis Aspidosperma cuspa Guapira spp Pilocarpus spp Phyllostylon brasiliensis Capparis f?exuosa Zanthoxylum pterota Phyllanthus botryanthus Cordia curassavica Machaon i a ottonis Gyrocarpus americanus Pseudobombax septenatum Plumer i a oudica Capparis tenu i sil i qua Acacia tamarindi folia Zanthoxylum monophyllum

Mor i son i a americana Arrabidaea corail i na

Myrospermum frutescens Celtis iguanea Matelea mari tima Chioccoca alba Cestrum al tern i folium Manihot aff. brachyloba Tabebuia chrysea

EE Zp PP Ac M Ch Pd Be Tb Pj RR P-R Ce Cp Ce

10 13 11 7

33

20 13 13 2? 27

7 7

13 ? 20

7 40 13 13 13 73

7 7

13 40

7 7

13 33 20 33

7 13 40 13 7

13 7

33 7

43 14 14 2? 14 2?

71 57 57 14

14 29 71

14 86 29

43

14

67 33 33 33 33 33

67

67 67 67 67 67

- 100 29 100 57 100 57 67

-

67 33 33 67

33 33

57 33 29 100

- 100 86 67 14 100 - ?7

14 57 33 14 33 71 67 57 67

- 67 29 67 29 100 86 100

67 67 67

20 40 40 20 20 20

40 20 40 40 80

60 80 20 60 20

40

20 20

20

20

14 29 29 43 14

86

14 14

60 100 80 71

29

14 71 71 43

43 57 14

40 80 43 40 100 80 14 60 29 40 14 20 29

-

14 20 100 40 43 20 40 43

14 14 14 14 14 43 43 29 14 14 29 71

9 9 9

36 18 45 9 9

27 9

14 43 86 71 57 57 86 86 100

100

55 64 36 27 55 36 55

27 27 82 82 73 36 27 18 27 73 18 9

45 45 9

73 27 9

45 27 36 45 9

27 45 55

9 18

27

22 11 11 44 33 44

44 22 11 22 56 33 89 44 67 89

73 100 91 100

78 67 56 33 89 78 67 89 22 33 22 67 33 22 67 44 11 67 33 33 11 56 44 33 67 11 11 11 78 44 44 56

11

6 18

24 6

18 18 59 24

6 76 24 24 12 18 35 18 53 53 88 76 65 71 53 24 82 65 71 53 65 76 82 29 35 71 59 24 29 12 35 35 41 53

6 18 47 47 18 24 24 24 47 35 18 35

6 12

6 12

24

12 6 6

44 6

6 62 56

6

6 31 88 38

75 38 44 94 6? 44 38 38 94 62 31 25 62 62 19 12 50 50 31 44 44

31 25 12 25 31

6 19 12 6

19 25 19 6

19 12

17 75 61 17 25 42 14 42 28

6 3 3 8

39 17 17 3

17 44 19 53 61

7 64 71 7 7

14

50 36 14 7

14 79

7 7

19 31 17 14 25 44 43 56 19 14 75 53 29 56 61 100 88 97 100 100 94 100 100 100 62 75 86 80

67 47 14 19 39 19 6

31 39 44 22 19 31 14

6 3 3

19 3

6 3 14 3 6

14 3 6

79 43 21 43 50 36 14 43 50 21 29 14 50 7

14

10 70 50 10 50 10 60 20 10 10 20 60 20 20 10 30 50 10 70

60 60 10 40 40 50 10 40 70 30 10 20 40

10 10 10 10

10

53 42 50 87 100 100 80 100 81 ?0 25

8 17

27

7 47 60

20 7 20 73

33 47 80

73 20 20 53 87 27

13 53 20 47

13

50

8 67

8 8

17 58

80 100 83 93 100 93 100 93 100

75

75 50 8

50 25 8

17

27 15 19 31 38

o 19 31

69 8

77 88 92 96 81 73 46 38 19 38 23 4

27 27 19 38 23 23 8

12 19 4 4 4 4

75

DOMINANCE TYPE EE Zp PP Ac ^ Ch Pd Be Tb Pj RR P-R Ce Cp Ce SPECIES

Amphilophturn paniculatum - - -

-57 91112 6 6 Cochlospermum vit?folium

-

-67 - - - - - 6 Erythroxylum cumanense --3S--9--6 Calliandra magdalenae --33 ---11-6 Strychnos fendleri

- - 33 20 - - - 6 12 -----

-

Marsdenia condensiflora - - 33 40

- 9 11 18 6 ----- -

Belenc i ta nemorosa - - 33 20 57. 9 11 18 19 - 21 Capparis indica 47 57 33 20 14 9 22 18

- 3 Platymiscium polystachium 27 14 33 -14

-

-12 - 3 Acacia macracantha 40 57 33 - - 18 22 41 12 3 Lantana c?mara 20 14 33 20 - 9 11 29 6 3 Platymiscium diadelphum 47 86 33 80

- - 44 41 12 3 Lonchocarpus atropurpureus 27 29 100 60 14 9

- 18 12 3 Simiraklu?ii 13 43 67 60 43 18 11 41 19 3 Humboldt i el la arb?rea 20 57 67 80 14 36 11 12 6 Helietta pleeana 27 29 100 80 29 27 11 53 31 Ruprecht i a spp 20 57 33 20 14 27 22 29 6

- - - - -

Bursera simaruba 60 71 67 60 - 36 11 12 6 ------ - Casearia zyzyphoides 27 57 33

- 29 27 33 29 12 Acacia glomerosa 87

- 67 60 29 - - 12 19 Macfadyena unguis-cati 87 71 100 100 14 27

- 18 6 ----- - Acacia pan i culata 73 57 100 100 43

- - 24 6 ----- - Machaerium spp 73 57 100 60 14 18 22 29 6

----- -

Guapira ferruginea 33 14 100 80 14 - 22 12 12 ----- -

Pithecellobium ligustrinum 13 14 67 40 - - 11 12 6 ----- -

Marsdenia altissima 7- 67 40 --11 12 6 Ximenia americana 13 29 67 - - 36 22 24 6 ----- 4 Trichilia trifolia 7 29 - - - 36 44 6 - 3 - - - - 4 Pithecellobium tortum 7 71

- - - 9 33 6 6 - -----

Pithecellobium carabobense 13 14 ----- 6 12 ------

-

Guazuma ulmifolia 27 29 -----6-3 Call iandra affinis

- - 33 - - -

11 -

12 ----- 4 Erythroxylum orinocense 7

-

33 40 - - - - 6 ----- -

Machaerium arboreum - 14 - 20 29 - - 24 38 Apoplanesia cryptopetala

- 14 100 80 - 18 - 29 12 - - - - -

Capparis verrucosa 73 71 100 80 14 27 22 41 ------ -

Bauhinia guianensis 87 86 67 40 14 55 22 12 ------ -

Achatocarpus nigricans 27 43 33 20 14 27 22 12 ------ -

Cal 1 iandra tergemina 7 43 100 40 - IB 11 6 ------ -

Capparis pachaca 27 57 67 20 - 64 44 35 ------ -

Coceo!oba padiformis 53 29 67 20 - 9 11 6 ------ -

Paul 1 inia pinnata 33 57 - 60 - 45 11 12 ------ -

Abutil?n giganteum 27 71 - 60 - 27 33 12 ------ -

Eugenia sp nov #4 7 14 33 - - 9 11 ?~ ------

Caesalpinia granadillo 20 - 67 20 43 18 - 24

Amyris ignea 27 29 100 60 - - 11 6

Seguieria americana 40 43 67 80 14 - - 24

Machaerium robiniaefolium 47 86 -

40 29 - 11 18 ------ -

Casearia praecox 20 14 33 60 29 - - 12

Capparis frondosa 73 57 33 60 -9-6 Maytenus spp 47 86 67 40

- 9 - 6 ------ -

Call iandra riparia 7 -67 80 14 - - 6

Bauhinia emarginata - - 33 - - 9 11 12 ------ -

Randia dioica 33 71 ----11 6 Casearia aculeata 33 29--14--6 Cordia thaisiana - 43 33 20 ---12 -------

Zanthoxylum culantrillo 20 14 33 40 - - - 6 ------ -

Randia venezuelensis 27 --

20 ---18 -------

Piptadenia pittieri 27 --20 14 --6 Lonchocarpus violaceus

--

67 40 14 --6 Bauhinia cumanensis 20 -67 40 -9-6 Schaefferia frutescens 7 14 - 20 14 - 33 6 ------ - Roche-fortia spinosa 7

-

33 20 14 - 11 12 ------ -

Aspidosperma varoasii 27 -33 40 43 --6 Euphorbia cot i n i fol i a 7 14 33 60

- - - 6 Bunchosia mollis 13 14

-

20 ---12 -------

Guapira pacurero 13 14 ---9-6 Maytenus karstenii 20 14 ---27 -12 -------

Piptadenia spec i osa ----29 9 11 Eugenia spp 80 71 100 60 14 36 11 Chrysophyllum sp 27 57 33 --911

--------

Brownea aroensis 40 43 -20 --11 Adelia ricinella 7

- 33 20 - -

11 ------- -

Call iandra qrac i lis 20 14 33 60 -9 Uitex compressa 13 14 67 20

------ ----- -

Crot?n niveus - - 67 60 -----------

Zamia muricata 60 43 -------------

Pachyptera hymenaea ?7 57 -------------

76

15 dominance-types; however, in at least nine of them their presence is less than 50 %.

Beard's system of formation-series

Four of Beard's series of formations are present: the seasonal series (controlled by decreasing rain fall), the dry evergreen series (determined by edaph ic water deficit), the montane series (controlled by altitude), and the swamp series (controlled by in creasing edaphic water excess). However, not all the formations in each series are represented here.

There are other edaphic formations which had not been described before in Beard's system. Also some

anthropogenic variants are sufficiently established to deserve inclusion in the series. The distribution of the formations is shown in the folded map (see end of this issue).

Relationships between the three systems of classification

Even though there is not a one-to-one association between the categories in the physiognomic and floristic classification (Fig. 5), a significant correla tion between them has been detected by Kendall's correlation coefficient (T=0.45; z = 9.59). The classes within each classification were ranked ac

cording to their structural and floristic complexity, in order to perform the test (Rand, 1971). The lack

of a complete association may be due to the fact that some of the physiognomy-types represent serai

stages or degraded community types derived from a single association. In some cases there is a high degree of association; i.e. all the evergreen thorny scrubs belong to the C. erecta dominance-type; all the closed evergreen thorny forests belong to the P.

juliflora dominance-type. However, each dominance-type is represented by more than one

physiognomy-type. There is also a lack of a one-to-one association

between physiognomy-types and formation-types, as well as between these and the dominance-types (Fig. 5). This reinforces the evidence that the vege tation pattern is represented by a gamut of serai

stages and degrees of human disturbance.

Description of the formations

Seasonal Formation series

The seasonal series, located on well drained soils, includes 6 lowland formations and 3 variants: ever

green seasonal forest, semi-evergreen seasonal for

est, deciduous seasonal forest, thorn woodland, cactus scrub, and desert; secondary deciduous sea sonal forest, deciduous thorn woodland, and

secondary cactus shrub.

Evergreen seasonal forest. The evergreen seasonal

forest is a three-storeyed forest with a closed tree

layer between 6 and 12 m high, overtopped by scat tered trees reaching 30 m. The lower storey, be tween 2 and 5 m, is discontinuous and includes small trees and shrubs (Table 4). In the uppermost tree stratum deciduous species, with compound leaves and umbrella-shaped crowns predominate.

The other two strata are formed mainly by ever

green mesophyllous species. Leaves are frequently compound in the middle strata and simple, thin and dark green in the lower strata. The under

growth is formed by small shrubs and coarse forbs

{Justicia, Hellconia, Aphelandra, Steriphoma, Cla vija, Canna), but the ground is almost bare. Lianas and epiphytes are present, but not too abundant.

Occasionally, a large tree, up to 3 m in diameter is found. All the stands belong to the Eugenia domi

nance-type, and it is one of the species-richest for mations (Table 3).

The evergreen seasonal forest occurs from 200 to 420 m alt. on the low coastal hills, and up to 900 m on the eastern Falcon Ranges. Soils are deep and

organic. Clearing for the establishment of pasture land has reduced the forest area in the last decades and at present only remnant patches are left in some areas, especially at the south of the Maritime

Valleys. Selective timber harvesting or clearance of the undergrowth for cattle raising or for the estab lishment of coffee plantations have degraded the structure to one or two layers with a tendency to deciduousness in the lower strata. However, the tree

composition of the upper storey is maintained, as

well as some structural features, such as absence of column cacti, presence of epiphytes and palms, as

evidence of their being derived from the more com

plex forests.

P-T D-T 77

Fig. 5. Relationship between the three classification systems. Physiognomy-types (PH): given in Fig. 3. Dominance-types (DT): as in Table 2. Formations (F): Cloud forest (CF); Evergreen seasonal forest (ESF); Semi-evergreen seasonal forest (S-ESF); Deciduous season al forest (DSF); Secondary deciduous seasonal forest (Sec. DSF); Thorn woodland (TW); Deciduous thorn woodland (DTW); Cactus scrub (CS); Secondary cactus scrub (Sec. CS); Desert (D); Gallery forest (GF); Dry evergreen bushland (DEB); Edaphic desert (ED);

Vegetation on the rock pavement (VRP); Herbaceous strand vegetation (HSV). The figures indicate the number of stands in each system assigned to the next type.

78

Semi-evergreen seasonal forest. Within the group of communities classified as semi-evergreen season

al forest, only three correspond to Beard's descrip tion; the rest includes more or less disturbed com

munities, which, however, retain elements of this

formation-type. The canopy is formed by the upper

layer, between 18 and 25 m, mostly of deciduous, umbrella-shaped trees. In the lower layer evergreen trees predominate. Myrtaceous shrubs are abun

dant, but there are few herbs and there is no ground cover. Lianas are abundant but epiphytes are scarce

(Table 4).

Table 3. Number of woody species per family in each formation. Formations labeled as in Fig. 5.

Family Formations

S-E Sec Sec CF ESF SF DSF DSF TW DTW CS CS D GF DEB ED VRP

Acanthaceae 5 3 6 2

Actinidaceae 1

Achatocarpaceae 1 1 1

Anacardiaceae 13 2 11 1

Annonaceae 1

Apocynaceae 6 6 3 3 2 1

Aquifoliaceae 1

Araceae 4 1 1

Araliaceae 2 1

Asclepiadaceae 114 3 11 1 1

Asteraceae 5 2 3 3

Bignoniaceae 21515 119 2 3 12 41 1

Bombacaceae 4 3 2 1

Boraginaceae 2565332 21 21 1

Burseraceae 2 13 3 12 2 2 1 2

Buxaceae 1

Cactaceae 14 44 44 44444 41

Caesalpinoideae 5 1216 158 6 5 36 44 5 6 3

Capparaceae 1 1012 135 7 5 56 15 3 2 1

Caricaceae 1

Celastraceae 114 5 1 1

Chloranthaceae 1

Clethraceae 1

Cochlospermaceae 1 1

Combretaceae 1 1

Convolvulaceae 1 11 11 11111 1

Cyatheaceae 1

Cycadaceae 1 1 1

Dioscoriaceae 1

Elaeocarpaceae 2

Ericaceae 3

Erythroxylaceae 1 13 2 1

Euphorbiaceae 14 5 23 198 8 5 44336 4 Faboideae 1012 23 166 6 2 13 3 1 1 Flacourtiaceae 14 6 7 3 1 2 1

Gesneriaceae 1

Guttiferae 6 3 2

Hernandiaceae 1 1111 1

Hippocrataceae 1 1

Table 3. Continued.

79

Family Formations

S-E Sec Sec CF ESF SF DSF DSF TW DTW CS CS D GF DEB ED VRP

Lauraceae 9 2

Lecythidaceae 1

Liliaceae 12 11

Loasaceae 1

Loganiaceae 1111

Lythraceae 1 1 1

Malpighiaceae 449113 22 111 2 2 Malvaceae 2 1 2

Marcgraviaceae 1

Melastomataceae 5 1

Meliaceae 5 6 2 1 1 1 Mimosoideae 7 11 25 27 13 8 4 35344 5 2 Moraceae 10 9 6

Myrsiniaceae 3

Myrtaceae 6 6 9 5 1 Nyctaginaceae 2 4 6 5 2 1 1 1 Olacaceae 2 2 1 1 Palmae 7 1 1

Phytolaccaceae 1 1 1

Piperaceae 10 3 2

Plumbaginaceae 1 8 1

Polemoniaceae 1

Polygalaceae 2 2 1

Polygonaceae 4 5 3 11 2 1 Proteaceae 2

Rhamnaceae 2 13 2 11 1 1 11 Rosaceae 2

Rubiaceae 19 10 15 10 4 2 2 3 1111 Rutaceae 4 8 11 7 5 4 1 1 Sapindaceae 3 11 8 8 2 1 1 1 Sapotaceae 12 2 1 11 11111 11 Simaroubaceae 12 11 11 1111111 Solanaceae 4 4 6 6 5 1 2 114 1 Sterculiaceae 13 3 2 1 Symplocaceae 1

Theaceae 1

Theophrastaceae 1232 21 11212 11 Tiliaceae 1 1 1

Turneraceae 1 1

Ulmaceae 2 2 2 111 1 1 Urticaceae 1 1

Verbenaceae 3 7 9 6 4 3 1 12 1 Vitaceae 2122122 21122 2 Vochysiaceae 1

Zygophyllaceae 2 2 12 2 1 12 2

Species total 202 211 292 236 93 87 51 41 51 24 49 45 38 11 Genera total 136 149 170 135 62 63 40 32 43 20 41 35 30 11 Families total 63 57 55 50 20 34 22 21 26 13 24 19 19 8

80

in the other two dominance-types. M. smithiana is

always present. Lasiacis ruscifolia, Solanum hir

tum, Alseis mutisii, Brachiaria fasciculata, Acalypha schiediana, Elvira biflora are also found in the undergrowth. There are some orchids, such as Oncidium cebolleta and Schomburgkia hum boldtii.

The semi-evergreen seasonal forest is the richest in woody species (Table 3). It has been greatly dis turbed in the Maritime Valleys and at lower alti tudes in the Mountain Ranges for the establishment of pastureland. To the east, the forests appear as

patches within a sabanna matrix and the size of the

patches has been decreasing continuously during the last decades. The forest is being replaced at a fast pace by the natural species Panicum molle,

Chloris inflata, Paspalum virgatum, Andropogon bicornis, or by introduced grasses such as Panicum

maximum, P. purpurascens, Cynodon plectostichi um, Pennisetum purpureum, Cenchrus ciliaris, and

Digitada decumbens. The deforestation is per formed on the flat as well as the sloping terrain,

which is producing serious problems of soil ero

sion. Frequently the highest trees are kept in the

pastureland and after abandonment, the wood lands are recognized to belong to the semi

evergreen seasonal forest from their presence. The forests located at higher altitudes have been im

poverished by timber harvesting.

Deciduous seasonal forest. The deciduous seasonal

forest, the most extensive formation in Falcon

State, comprises 55 stands classified as non-thorny deciduous forest or woodlands, distributed all over the State. There is one tree stratum 5 to 10 m high,

which may be closed or open. In some communities there are occasional emergent trees reaching up to 12 m. There are no large trees. There are but few lianas and the epiphytes are restricted to small

xerophytic bromeliads; buttressed trees, ferns, palms and stilt roots are absent but column cacti are conspicuous. Most of the tree species are decid uous; the few evergreen species are sclerophyllous.

Many of the species have compound leaves and there is a tendency to microphylly. An understorey of shrubs and semi-shrubs is usually found, which becomes denser as the tree coverage decreases. The

81

ground is almost bare, with few forbs and grasses, except for scattered colonies of bromeliads. In the

most disturbed communities the undergrowth is formed by a dense layer of shrubby cacti.

The most typical dominance-type within the deciduous seasonal forest is Bourreria cumanensis

Phyllostylon brasiliensis-Bulnesia arb?rea, which occurs in the Coastal Plains, the Falcon Ranges and the Coastal Piedmont between 10 and 600 m alt. It constitutes a transition between the semi-evergreen seasonal forest and the next type, comprising Tabebuia billbergii communities. The latter, which lie toward the xeric end of the gradient within the

deciduous seasonal forest, are to be found in all the

physiographic provinces. The undergrowth is heterogeneous, and in the T

billbergii dominance-type it may be dominated ei ther by Lippia spp, Sida aggregata, Crot?n flav ens,

Opuntia wentiana, C. erecta, or Cordia curassavi

ca. Either this last species or Bastard?a viscosa may be an undergrowth dominant in the B. cumanensis P. brasiliensis-B. arb?rea forests. In both domi

nance-types, B. chrysantha or B. humilis may form extensive colonies that cover the ground. Other spe cies present in the lower layer include Cnidoscolus urens, Jatropha gossypifolia, Melocactus caesius,

M. smithiana, Melochia tomentosa, Sporobolus pyramidatus, Solanum argillicolum, Eragrostis ci lia ris, A. pentagonus, Ocimum micranthum, Wede lia parviflora. Most of the undergrowth species do not have a high presence percentage in any domi

nance-type and they appear in patches of differing species composition.

To the east, the deciduous seasonal forest is

represented by stands of Crot?n heliaster, located in the Maritime Valleys and in the eastern extremity

of the Alineaci?n Septentrional, in patches within the pastureland. They are all secondary forests and

woodlands in which C. heliaster behaves as an in vader. They are characterized b*y the presence of dense B. humilis or Aechmea aquilega colonies

forming the ground layer. Their geographical loca tion within the distributional area of the Z. pterota

Machaerium spp-Eugenia spp forests could suggest that the former are derived from the latter after

clearing of the original semi-evergreen seasonal for est and subsequent abandonment; however, there

82

are no evidences to support this hypothesis. The

patchy pattern within the pasturelands and the ab sence of the species belonging to the semi-evergreen seasonal forests makes it difficult to suggest that

they can evolve towards their former community type. A different situation occurs with the C. heliaster forests located in the western Coastal

Plains, in which the accompanying species, as well as the location suggest that they may have derived from the T. billbergii deciduous seasonal forest.

The Pithecellobium dulce-Capparis hastata

stands, distributed between 20 and 600 m altitude, also belong to the deciduous seasonal forest forma tion. In the Falcon Ranges they are located on the southern slopes; and represent a xeric extremity

within the formation. The undergrowth species found most frequently are O. wentiana, B. viscosa

and M. tomentosa. In the Maritime Valleys they oc cur on the lowest, nutrient-poor, saline soils, next

to the flood-prone terrains. The trunks are thin and whitish. The accompanying evergreen tree species are very conspicuous during the dry season. The

most frequent undergrowth species are A. pentago nus, A. halimifolia, A. williamsi, M. smithiana, Setaria rariflora. Dense patches formed either by B. humilis or by B. chrysantha often cover the ground. The physiognomy and environment reminds one of the dry evergreen forests of the dry evergreen for

mation series; however, deciduous species predomi

nate and the community's appearance changes

notably with the seasons.

Finally, within the deciduous seasonal forest for

mation, three C corlarla woodlands are found.

They occur to the west, in the Coastal Plains and in the Coastal Piedmont. They represent a transi tion between the thorn woodland and the T bill

bergii deciduous seasonal forest, from which they have probably derived. They resemble the thorn woodland in structure, except for the scattered tree

layer that overtops the thorny umbrella-shaped trees, as a witness of their origin as deciduous sea

sonal forest. This feature gives them the non

thorny deciduous character. The presence of an al most closed prickly pear cactus (O. wentiana) layer and of other invaders, such as Ipomoea carnea and B. viscosa, are evidence of the high degree of dis turbance.

The deciduous seasonal forest has been greatly disturbed by human activity. Large tracts of forest have been felled for the establishment of pasturelands. After abandonment, nearly pure stands of Aspidosperma spp follow, with a low uni form stratum of this species, overtopped by a scat tered layer of this and other tree species. These stands have been classified as secondary deciduous seasonal forest. They are located to the west of the

Coastal Plains and Coastal Piedmont, next to patches of B. cumanensis-P. braslliensis-B. arb?rea

and T. billbergii deciduous seasonal forests. Their flora has been impoverished as compared to the deciduous seasonal forests (Table 3), but they still have species belonging to it. Since the units are small the possibility exists that they will return to their former condition. However, whether this hap

pens or not depends on the pressure by cattle and goat on the tree seedlings and their capacity to sur vive browsing and trampling.

Thorn woodland. The thorn woodland is a very ex tensive formation located in the Coastal Plains,

where it can reach the seashore, in the Coastal Pied mont and in the Central Depressions, mostly on flat terrain. It comprises mainly closed to desertic

woodlands (Fig. 5); however, the vertical structure is very variable and some units have been classified

as forests and 'cardonales'. The tree layer, from 3

to 5 m high, is dominated by thorny evergreen microphyllous species, mostly legumes. Trees branch near the ground (1 to 2 m) and are umbrella-shaped. There are sclerophyllous trees and shrubs, but orthophylly predominates, both in species number and in plant cover. The under growth is dominated by shrubby cacti. Ground vegetation is very sparse and grasses are almost ab sent. The column cacti may overtop the tree layer.

The most extensive thorn woodlands belong to the P. juliflora dominance-type. Their large exten sion may be related to the ability of Prosopis to ob tain water from underground storage. This species does not show xeromorphic features. It evades wa ter stress by means of a deep rooting system, as shown by the high transpiration rates maintained along the day and even during the dry season. The Coastal Plain soils, where this species competes

with advantage, must have a large water retention

capacity and most probably upward flow from the water table maintains the storage in the deep soil

layers.

The thorn woodland has been the domain of

goats since the arrival of the Europeans and the

vegetation is impoverished, specially the palatable species. Though this vegetation type has been con

sidered 'typical' of the semiarid coastal zone, and even a climax (Tamayo, 1967), it is likely that it represents a secondary community-type, which could become established due to the tenacity of

both P. juliflora and O. wentiana, whose dissemi nation is favored by goats. The former is dispersed internally via the digestive tract, where seeds are

scarified; the cactus regenerates vegetatively from the joints carried on the goats' hide. Other evi dences to support the suggestion that the P.

juliflora woodland is a secondary community-type are the presence of elements of the deciduous sea sonal forest in some of the stands, as well as the oc currence of patches of that formation intermingled with it. It appears that this group of thorn wood lands has been derived from the deciduous seasonal

forest, in agreement with Tamayo's (1963) proposal; however, it has become sufficiently established so as to be considered a formation-type on its own.

In addition to Opuntia, the most common spe cies to be found in the undergrowth, are S. pyrami

datus, M. caesius, C urens, Allionia incarnata, E.

ciliaris, A. halimifolia, Caraxerum vermicularis, Euphorbia dioica, Ayapana squarrosa, B. viscosa,

J. gossypifolia, C. erecta and C. flavens however, only the last four species, may become dominant in the understorey.

There is a variant of the P. juliflora thorn wood lands, in which the dominant species adopts a

shrubby growth form and branches from the

ground, probably as a consequence of goats brows

ing the seedling apices. In this case the vegetation becomes almost impenetrable, cluttered by the tree branches and shrubby cacti.

Even though most of the stands belong to the P.

juliflora dominance-type, other dominance-types are also represented. Whenever the column cacti become abundant and co-dominate with P.

juliflora, the stand was classified in the P. juliflora

83

Ritterocereous spp dominance-type. The accom

panying tree species and the undergrowth composi tion do not differ from those of the P. juliflora

woodlands. The P. juliflora-Ritterocereus spp thorn woodland, which represents a transition be tween this formation and the cactus scrub, includes

woodlands and 'cardonales'. Both physiognomy types differ from each other in the relative height of the trees and the column cacti. In the

'cardonales', the cacti become very conspicuous be

cause they overtop the tree layer, which forms a

very uniform canopy of umbrella-shaped crowns. In the woodlands, the trees are as high or higher than the cacti. In both physiognomy-types the column cacti have a bole attaining more than a me ter high and more than 30 cm diameter, with many branches and are heterogeneous with regards to

form, size and probably age. The undergrowth may be formed by a closed layer of O wentiana. It oc curs in the Central Depressions and in the Coastal Piedmont.

In the Paraguan? Pen?nsula, three C. erecta thorn woodlands are found. They have been classified as

open evergreen thorny woodlands and differ from the C erecta shrublands because the shrubs are

overtopped by a tree layer and they are located on

non-calcareous soils. Two of these communities oc

cur in a less xeric environment at 120 to 200 m alt. around Santa Ana hill, next to a T billbergii forest. This site has been cleared for the establishement of

crops mainly sesame, sorghum and corn and nowa

days is one of the rural areas with higher human

density. The possibility that a deciduous seasonal forest occurred at this site cannot be discounted.

The B. cumanensis-P. brasiliensis-B. arb?rea, P.

dulce-C hastata and C. corlarla stands included in the thorn woodland formation might have been derived from the deciduous seasonal forest since, even though their physiognomy corresponds to the

former, species typical of the latter grow here.

However, they are evergreen and thorny. They are

located in the proximity of villages or pasturelands. Within the seasonal formation-series, the thorn

woodland represents a stage in which a drastic reduction in woody species number occurs (Ta ble 3).

84

Deciduous thorn woodland. The deciduous thorn

woodland, not included in Beard's classification

system, resembles the thorn woodland in structure; except that deciduous species dominate the tree stratum. It can be barely distinguished from the thorn woodland during the wet season, but in the

dry season its appearance changes considerably. It is not clear whether these communities have der ived from deciduous seasonal forests; although this

possibility cannot be discarded, features to support this view are not present, for most of the deciduous trees are low thorny umbrella-shaped legumes.

They differ from the deciduous seasonal forest in the predominance of thorny species, their lower

canopy, and the abundance of shrubby cacti in the

undergrowth. Another feature is the presence of column cacti, which can be very abundant in some stands (Table 4). Woody species composition is im poverished (Table 3).

The deciduous thorn woodland, represented by forests, woodlands and 'cardonales', comprises

several dominance-types (Fig. 5). All the Cercidium praecox stands are included in this formation. They are distributed in all the Physiographic Provinces within the dry region, on disturbed lands in the

neighbourhood of villages. The dominance of C. praecox may be due to the fact that it is used nei ther as firewood nor for timber. Some time ago it

was gathered for manufacturing soap, but this

practise has been abandoned. The pods are not

palatable for goats and it is one of the few species that is not eaten by them. For these reasons C prae cox has an advantage over other woody species in such semi-artificial landscapes. P. juliflora and Rit terocereus may codominate with C. praecox, and

Pereskia guamacho, A. tortuosa, Mimosa arenosa

and Capparis odoratissima are very abundant. C

erecta, O. wentiana or I. carnea may dominate in

the undergrowth, whose composition is similar to that of the P. juliflora woodlands.

The C erecta stands classified as open or desertic deciduous thorny woodlands, are also included in the deciduous thorn woodland. Even though the shrub dominates, the degree of cover of the accom

panying trees is higher than that of C erecta and the structure and appearance differs considerably from that of the C. erecta shrublands. The under

growth does not differ from that of the P. juliflora woodlands in composition but it is sparser. They grow on non-calcareous soils.

Cactus scrub. The next formation of the seasonal series is the cactus scrub, described as a thorny vegetation-type in which the column cacti occur scattered among the trees and shrubs, which are low and sparse. The total plant cover is low. The

undergrowth, formed by cacti, forbs, ephemerals and grasses, is sparse and patchy and the ground is almost bare. Even though the canopy may be decid

uous, evergreen species predominate among shrubs

and trees.

Of the 21 'cardonales' present in Falcon State, only eight stands agree with Beard's description of the cactus scrub (Fig. 5). They are located at the north of the Coastal Plains, bordering the desert or the thorn woodland. The occurrence of patches of cactus scrub intermingled with other formation

types, as well as evidences of tree felling in some of

them, suggest that they might be secondary com munities or impoverished thorn woodlands. They could also be remnants of larger cactus scrubs that have been either encroached by desert or invaded

by P. juliflora. Most of them belong to the Rit terocereus dominance-type, in which R. griseus or

R. deficiens are dominant. The dominant species in the undergrowth may be O. wentiana, A. halimifo lia, or C erecta, and the accompanying species are the same as those found in the P. juliflora wood lands.

Other 'cardonales', consisting of dense, almost

pure stands of column cacti, do not correspond to the cactus scrub in Beard's classification, because the vegetation is too dense and high. They have been classified as secondary cactus scrub. The abundance of column cacti, together with the

uniformity in height of the individuals, suggest that these communities represent early stages of a

secondary succession, taking place after abandon ment of cleared tracts of land, through syn chronized germination and establishment of Rit terocereus. The structure is not simpler, but cluttered and it cannot be considered intermediate between the thorn woodland and the desert along the mesic to xeric climatic gradient. The cacti are

small and branch very little and near the ground, which attest to their recent origin. They all belong to the Ritterocereus spp dominance-type, and are

mostly deciduous and non-thorny. The communi

ties are reduced in extent and located to the south of the Coastal Plains, in the Coastal Piedmont and in the Central Depressions, bordering the decidu ous seasonal forest, from which they have probably derived. They belong to the seasonal formation se

ries since they grow on well drained soils. Their

high species richness as compared to the cactus scrub (Table 3), is another evidence of their higher complexity.

Desert. Only 10 of the 46 desertic physiognomy types represent the desert formation-type within the seasonal formation series (Fig. 5). They are lo cated on the northern fringe of the Coastal Plains. The desert appears either as scattered herbs, shrubs and low trees on a bare plain or as patches of vege tation complexes scattered on a bare plain. In both cases P. juliflora is the most abundant species. The patches are small (2 to 3 m in diameter) and rather dense. The vegetation within the patches resembles a thorn woodland; however trees are dwarfed and with their branches swept to the leeward due to wind action, and the flora is poorer (Table 3). The density of patches, as well as their size and the den

sity of vegetation within the patches decreases to ward the shore untill a point is reached where they contain dead trees. This fact, in addition to the

presence of remnants of deciduous seasonal forests

within the desert matrix, suggests that this may be a secondary formation. It is unlikely that vegeta tion will re-establish itself, for much of the exposed soil has probably been removed by wind and water.

The dry evergreen formation series

Vegetation structure and physiognomy are largely determined by the limiting moisture supply im

posed by topographic or soil conditions, which override the effect of rainfall seasonality. Two for

mations are represented in Falcon: the dry ever

green bushland and the vegetation on the rock

pavement.

85

Dry evergreen bushland. The dry evergreen bush land consists of a low layer (0.5 to 2 m high), domi

nated by evergreen sclerophyllous trees and bushes, with a tendency to microphylly, overtopped by scat tered trees and column cacti. Thorny species pre dominate. Ground vegetation is remarkably scarce, consisting of small Cactaceae and a few forbs and grasses (Table 4). The sclerophyllous shrubs show a hemispherical growth habit, with no obvious trunk, and the landscape appears greyish-green due to the whitish branches and the light green foliage. Plant cover is low, sometimes less than 50% and the soil surface is exposed. Most of the stands belong to the

C. erecta dominance-type. In the undergrowth, Malvastrum americanum, A. incarnata, A. squar

rosa, Aristida adscensionis and A. pittieri may be come abundant, but the most frequent species are

M. caesius and O. wentiana.

The dry evergreen bushland occurs in the Coastal

Plains, at 20 to 90 m alt. and in the Central Depres sion between 180 and 200 m alt. It often lies in close proximity to the thorn woodland; however it

differs both in structure and in species composi tion. The differences are caused by the soils, which are sandy and overdrained, calcareous and fre

quently overlain by gravel or pebbles. The whitish terrain surface emphasizes the landscape's appear

ance. Forty-six species in 36 genera and 23 families have been listed (Table 3).

Rock pavement. The vegetation on the rock pave ment consists of low, scattered shrubs, herbs and

cacti growing on a desert pavement, in the central

portion of the Coastal Plains and in the Central

Depressions. The few tree species are almost entire

ly confined to the dried water courses. The land

scape is dominatd by the greyish sclerophyllous bushes and the low globose cacti outstanding against the desert varnish. The most abundant spe cies are C. erecta and M. caesius, on the rock pave

ment and C praecox, P. juliflora, C odoratissima and Haematoxylon brasiletto along the water courses.

The narrow fringe of littoral hedge, located be tween the strand herbaceous vegetation and the thorn woodland along the coastline in the isthmus and the eastern shore of the peninsula, should

86

probably be included in the dry evergreen forma tion series. This area is subjected to the winds load ed with salt spray that come from the sea. The dominant species, Conocarpus erectus, grows stunted on the sand dunes which it fixes with its

rooting system on the windward side and its branches extended in the wind direction. Other spe cies present are Sporobolus virginicus, Egletespros trata, Argythamnia argothamnoides. The tracts of littoral hedge are smaller than the minimum area

and have not been field surveyed in the present study.

Montane Formation series

The complete series cannot be represented in Fal con State because, on the one hand, the lowlands are dry and thus the gradient goes upwards from xeric to humid vegetation types. On the other hand, the mountains are not high enough to attain the

ecological conditions in which the last formations of the series develop. There are only two montane

formations in the study area: the palm brake and the mountain rain forest. The former, a reduced

community dominated by Geonoma paraguanen sls, is confined to a small area at the summit of Santa Ana hill (850 m) on the Peninsula. Here, the dominant species adopts a dwarf habit, probably due to the prevailing strong winds.

Below the palm brake, between 700 and 800 m

alt., there is a mountain rain forest; however, the

largest extension of this formation is located be tween 1000 and 1 500 m alt. on the eastern extremi

ty of the northerly mountain range. There are small

patches of cloud forest scattered on the summits of

the other ranges too. These represent remnants left on the least accessible sites.

The forests have three layers, with two tree layers at 14 to 20 m and at 10 to 12 m high. The third lay er, formed by shrubs, palms, ferns and small trees, reaches up to 2 m. The outstanding feature is the

great profusion of epiphytes, among which

bromeliads, orchids, ferns, mosses and liverworts are found on tree trunks and branches through the

whole profile. Lianas are rare, tree crowns are

rounded and small. The soil is dark brown, organic

and stays soft and humid all year round. All the stands belong to the Eugenia spp

dominance-type. Lauraceae, Piperaceae and

Moraceae become prominent families, the former

being specially conspicuous among the higher trees. Dark green thick simple mesophyllous leaves

predominate. There are few trees with plank but

tresses, but trunk diameter is smaller than in the

evergreen seasonal forest. Evergreen species pre

dominate. The species list includes 202 identified

woody species, in 136 genera and 63 families; how ever, these may be underestimated since it has not been possible to identify all the specimens collect ed. Some of the species found only in this forma tion are Palicourea petiolaris, P. perquadrangularis,

Miconia aeruginosa, M. racemosa, Gonzalagunia

dicocca, Rapanea ferruginea, Psychotrla costanen

sis, P. guadalupensls, Plukenettia sp, Pleurothallis

camensis, Evodlantus funifer, Epldendrum elonga tum, E. heterodoxum, E. lividum, and many more.

Swamp Formation series

This series is represented by the mangrove wood

lands, of which two types can be recognized in the

study area: the forests, that occur along the bays and the coast within the Maritime Valleys Province, and the shrubby patches of the arid zone along the western coast of the Paraguan? Pen?nsula and around the Golfete de Coro. The mangrove forests are three storeyed, with the closed canopy at 20 to 26 m high, an open layer at 10 to 18 m and another closed stratum at 3 m. There are few shrubs, epi phytes or lianas. Palms may be present. Towards the seashore their height and floristic and structural

complexity decreases. The dominant tree species are Rhizophora mangle, Avicennia germinans and

Laguncularia racemosa.

The arid zone mangrove woodlands are restricted to a few spots along the coast. They are extremely simple in structure. They consist of almost pure stands of A. germinans 1 to 3 m high, growing around small ponds and tidal inlets and surround ed by halophytic herbaceous vegetation, mainly of Sesuvium portulacastrum, Heterostachys ritteriana and Salicornia sp. It is hard to say whether these

communities are remnants of a larger one or early

stages of developing mangrove woodlands. It has been suggested that the whole Golfete de Coro was

occupied by a mangrove forest; however, there are no evidences to test this hypothesis. The presence of a forest was not reported by Americo Vespucci in his description of the vegetation of the Venezue lan coast, along which he travelled with Ojeda from Surinam to the Venezuelan Gulf in 1499.

Next to the mangrove woodlands, submerged communities of the vascular plant Thalasia are

found. These are very rich habitats, where many marine species in their larval stages strive. Among the algae, Gracilaria, Gelidiela, Halimeda and Sar

gassum are abundant.

Other edaphic formations

There are three community-types, not considered in Beard's system: the herbaceous strand vegetation, the gallery forest and the edaphic desert, which lie side by side with the seasonal formations and are determined by edaphic conditions.

The herbaceous strand communities occur along the eastern coast of the Paraguan? Pen?nsula,

where they have been classified as savanna

(Tamayo, 1941) and in small patches along the in land coastal fringe. The formation comprises a het

erogeneous group of communities in which floristic

gradients perpendicular to the shoreline are found. The seaward extremity is dominated by halo

phytes, such as Mallatonia gnaphaloides, S. por tulacastrum, H. ritteriana, Salicornia spp, among

others, none of which reaches true dominance. Semishrubs and small shrubs with a prostrate hab

it, such as E. prostrata, Heliotropium curassavi

cum, Crot?n ovalifolius, C vermicularis, Tribulus

cistoides, occupy the continental extremity. Some

grasses are present (S. pyramldatus, S. virginicus, Cenchrus pilosus); however, they grow very sparse ly; thus, these communities cannot be considered

savannas, since forbs predominate. The sandy soils and the winds are the limiting factors. In recent

years, the communities located in the eastern coast of the Peninsula, have been gradually invaded by O wentiana due to an increase in the goat and donkey populations.

87

The gallery forests occur in the Coastal Plains and Central Depression, along the rivers and streams. They are one storeyed evergreen thorny

forests with a closed canopy at 8 to 10 m. They be

long to the P. juliflora dominance-type. Here, the dominant species adopts a tree habit, with a 5 to 8 m bole and a very extended umbrella-shaped crown. Lianas are very conspicuous and Arrabidea

mollissima may codominate with P. juliflora. O wentiana is the most frequent species in the under

growth and, though it is not abundant, it is con

spicuous in the otherwise sparse species poor lower

layer. S. argillicolum, Ruellia and Cardiospermum are also frequent in the understorey. Forty-nine woody species have been listed, distributed in 41 genera and 24 families (Table 3).

The gallery forest is particularly noticeable in the areas occupied by thorn woodland, cactus scrub, and desert, where its width has been exaggerated (Hueck, 1960, 1966). Even though this formation is protected by law (Ley Org?nica del Ambiente), it has been greatly disturbed for the establishment of

cropland and it has disappeared at localized spots (Pia, 1980).

The edaphic desert consists of a low layer (2 to 4 m) of scattered trees, mainly deciduous

mierophyllous legumes; evergreen shrubs predomi nate in the lower stratum. Semishrubs, forbs and

grasses grow sparsely. The ground is almost bare, except for the small cactus M. caesius which, even

though very sparse, becomes conspicuous (Ta ble 4). Other species present are Opuntia caribaea,

O wentiana, A. incarnata, S. pyramidatus. This

formation-type differs from the deciduous thorn woodland because vegetation is sparser and lower; it cannot be included in the seasonal formation se ries because aridity is determined by the steep dis sected slopes and the gravelly surfaces rather than

by climatic conditions. This formation might have derived from the deciduous seasonal forest, but the evidence is not sufficient to test this hypothesis. The upper tree layer is absent and the vegetation is scattered. The edaphic desert is sufficiently extend

ed, stabilized and recurrent in similar environments so as to deserve being introduced as a new category. It occurs in the Coastal Plains, the Coastal Pied

mont, the Central Depressions and the Falcon

Ranges, between 80 and 400 m alt. It belongs to C

88

erecta or C. corlarla dominance-types. It is richer in

species than the seasonal desert (Table 3).

Discussion and conclusions

The physiognomic classification is artificial, but

easy to understand and to handle by a wide range of users, including non-scientifically trained per sonnel. It has practical significance for planners and policy makers, as well as for agricultural, sil

vicultural, faunistic, and ecological research. It also allows monitoring vegetation in a simple fast way.

The life-form and structural categories em

ployed, as well as the scales and the techniques for

their assessment were chosen from those suggested in the literature (Dansereau, 1957; Fosberg, 1967;

Mueller-Dombois & Ellenberg, 1974); however, criteria based on local characteristics and on the

necessity to produce a comprehensible system, were

applied for the data analysis and the structural

description. The categories, terms, and techniques employed were previously defined, and a check

sheet was devised and used during field work, in or

der to minimise as far as possible the subjectivity, which is unavoidable in vegetation studies. Special care was taken to avoid circular reasoning and the

data on environment and vegetation were gathered and analysed independently previous to the in

terpretation (Matteucci & Colma, 1982). Local vegetation studies frequently consist of

relating the stands to some previously adopted clas

sification. Keys have been prepared to simplify their assignment to the correct category (Fosberg, 1967; K?chler & Montoya, 1971; UNESCO, 1973).

This approach may lead to more subjective deci sions than necessary. Also, valuable information

could be lost due to unwilling oversight of details not considered for the definition of classes. We went the other way round and first obtained records in a way as objective as possible, producing the classification from the analysis of the data.

However, the information was gathered with

enough detail and consistency as to allow the in

terpretation of results in terms of the existing clas

sification systems and enable comparisons with the

vegetation of other regions.

That vegetation and climate are closely related has been recognized for a long time. However, the simplistic approaches such as those proposed by

Holdridge (1959) and Sarmiento (1968), should be taken with care. It is unfortunate that Holdridge's

model has gained favor in Venezuela, through its application by Ewel & Madriz (1968). Any associa tion between climatic parameters and vegetation types in Falcon State should be considered with caution due to the lack of adequate climatic data (Matteucci & Colma, 1986). More than half of the meteorological stations are located in towns or

villages, or in protected lowlands and valleys and their distribution is uneven. Relief heterogeneity precludes the extrapolations to nearby areas. The observation intervals are short in most cases and only a few of them collect both temperature and ?vapotranspiration data.

The 39 stands of natural vegetation within which meteorological stations are located, are plotted in Sarmiento's (1968) orthogonal system (Fig. 6a). The cactus scrub and the desert fall within the thorn scrub niche, and not in the desert and semi desert environments as would have been expected. This is probably due to the fact that rainfall seaso

nally and rate of ?vapotranspiration have a greater influence on physiognomy than mean annual tem

perature and precipitation. The possibility that the desert and cactus scrub stands are degraded thorn woodlands may be rejected on the grounds that both fall within Bailey's arid Moisture Province

(Fig. 6b). In previous studies, the constraints imposed by

edaphic factors have not been considered. The dry evergreen bushland has been classified as thorn

woodland or cactus scrub (Ewel & Madriz, 1968; Hueck, 1960, 1966; Pittier, 1937; Sarmiento, 1972,

1976; Smith et al., 1973; Tamayo, 1958) without re gard to the distinctive physiognomic and environ

mental features. In none of the papers mentioned the edaphic desert is recognized. It has probably been included in the deciduous bushland, even

though the former is lower and sparser. In the

edaphic desert vegetation is controlled by terrain

factors, a distinction that has not been mentioned in reference to the deciduous bushland. The possi bility remains that the edaphic desert is derived

89

29H

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85 ?3 O

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06

70 4o 4o

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THORN SCRUB

1 ?0

% 40

3o

4p

3o 1 1

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TROPICAL FOREST SUBTROPICAL a SUBMON-, SUBTROPICAL ft TROPICAL SUB TANE DECIDUOUS SEASONj MONTANE FORESTS AL FORESTS

lo

I0RN FOREST , -8-Hr

1,

ra-~n12 is 14 MEAN ANNUAL PRECIPITATION (dm)

fe iU te fe iV

a

?BlO^g, ^12

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0 #7

4 4 1

2

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ARID _L_

SEMIARID -L.

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I DRY ? SUBHUMID MOIST SUBHUMID

_I_L.

2

.2

.2 2

3 4 5 6 7 8 9 BAILEY'S ANNUAL MOISTURE INDEX

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10 II 12

Fig. 6. Relationship between vegetation and climate. Thirty-nine stands are plotted in Sarmiento's orthogonal model (6a) and in relation to Bailey's Moisture Provinces (6b). Subdivisions within the graphs correspond to the formation-type niches (6a) or moisture provinces (6b). 1) CF; 2) ESF; 3) S-ESF; 4) DSF; 6) TW; 7) DTW; 8) CS; 10) D; 12) DEB; 13) ED; 15) HSV.

from the deciduous seasonal forest; however, there are no structural or floristic elements to support the hypothesis, neither the ability to regenerate a

forest, if it ever existed, for not only the genetic pool has been lost but also the present soil condi tions would preclude its establishment.

Temporal relationships have also been neglected in previous studies. Either vegetation types which

differ in origin have been classed together or vari ous disturbed community types have been classi fied in separate groups even though their origin is the same. For example, the deciduous bushland described by Smith et al. (1973), and regarded as a new vegetation type by Sarmiento (1976), is derived from the deciduous seasonal forests and as such has been classified in the present paper. It is lower

90

than the deciduous seasonal forest described by Beard, but higher than the deciduous thorn wood land. The tree species in the upper layer belong to the deciduous seasonal forest, and they lie side by side with the latter. It seems obvious that their structural features are due to human interference; however, since seed sources have been left and the disturbance has not altered the soil, there is no rea son to assume that the forest will not recover.

Whether this happens will depend on the regenera tion pathway followed by the secondary successin

(cf. Van der Maarel, 1984). The cactus scrub as defined by Sarmiento (1976)

includes a tree layer of up to 8 m high, and does not correspond to Beard's description of the cactus scrub. In the present study, the existence of such a tree layer, as well as the geographical location, are considered as an indication that these cactus scrub communities owe their existence to anthropogenic forces operating on the deciduous seasonal forest and have been classified as secondary cactus scrub or as deciduous seasonal forest.

A similar situation is posed by Beard's (1944) and Sarmiento's (1976) descriptions of the thorn wood land. According to the latter, the thorn woodland has two tree layers and the upper layer attains 8 m of height. On a close inspection it turns out that the

species in the upper tree layer are those of the deciduous seasonal forest; thus, in the present study the stands conforming to Sarmiento's

description have been classified as deciduous sea sonal forest or secondary deciduous seasonal for est.

Asprey & Robbins (1953) have recognized a new formation: the cactus-thorn scrub, in which the column cacti are very conspicuous and overtop the closed tree layer. This structure is present in Falcon State too, but it has been classified as thorn wood land, deciduous thorn woodland or secondary cac tus scrub, depending on the species composition and the history of the site.

A dynamic, holistic approach to the study of

vegetation discloses the temporal and spatial rela

tionships. However, only a thorough knowledge ob tained through intense field work permits this kind of interpretation.

References

Asprey, G. F. & Robbins, R. G., 1953. The vegetation of Jamai ca. Ecol. Mon. 23: 359-411.

Bailey, H. P., 1979. Semi-arid climates: their definition and dis tribution. In: A. E. Hall, G. H. Cannell & H. W. Lawton (eds), Agriculture in semi-arid environments. Ecological Studies Vol. 34, pp 73-97, Springer, Berlin.

Beard, J. S., 1944. Climax vegetation in tropical America. Ecol ogy 25: 127-158.

Beard, J. S., 1949. The natural vegetation of the Windward and Leeward Islands. Oxford For. Mem. 192 pp.

Beard, J. S., 1955. The classification of tropical American vege tation types. Ecology 36: 89-100.

Colma, A. & Matteucci, S. D., 1982. An?lisis regional de la

vegetaci?n y el ambiente del Estado Falc?n: Los suelos. Universidad Nacional Experimental Francisco de Miranda, Coro. Falc?n.

Dansereau, P., 1957. Biogeography: an ecological perspective. Ronald, New York.

Ewel, J. & Madriz, A., 1968. Zonas de vida de Venezuela, Memoria explicativa sobre el mapa ecol?gico. 2da ed. Edi ciones del Fondo Nacional de Inve