soil dwelling macro-invertebrates in intensively grazed dairy pastures in pennsylvania, new york and...

Soil dwelling macro-invertebrates in intensivelygrazed dairy pastures in Pennsylvania, New Yorkand Vermont

R. A. Byers* and G. M. Barker

*USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA, USA, and Landcare Research, Private Bag 3127, Hamilton, New Zealand

Abstract

This study estimates the relative contributions of envi-

ronment and farm management strategies in in¯uen-

cing soil faunal assemblages and attempts to identify the

species with potential to affect sustainability of inten-

sive grazing management systems in the north-eastern

USA. It arises because of the change from con®nement

feeding of dairy cattle, consequent upon concerns about

negative environmental effects, the rising costs for

machinery and housing, and reduced pro®t margins,

together with the absence of data from which the

consequences of such change on the soil fauna may be

predicted.

Macro-invertebrates were sampled in soil from sev-

enty-eight grazed pastures on twenty-one dairy farms

in Pennsylvania, USA, in the spring of 1994. On ®ve of

these farms, macro-invertebrates were sampled (four

pastures per farm) in the spring, summer and autumn

seasons of 1994, 1995 and 1996. In 1997, macro-

invertebrates were sampled in soil during spring,

summer and autumn from (four pastures per farm) on

three farms in New York, and during spring and

summer on three farms in Vermont. Species richness

ranged from two to twelve species (mean 6á4) per

pasture site in Pennsylvania and ®ve to eighteen species

(mean 10á7) in New York and Vermont. The commu-

nities were dominated at most sites by earthworms.

Earthworms were correlated with soil basal and sub-

strate-induced respiration/carbon ratio, and soil mois-

ture, but were negatively correlated with cows per

hectare and herbage biomass in Pennsylvania. Sitona

larvae were recorded at nineteen of the twenty-one

farms during the spring of 1994 across Pennsylvania

and occurred at populations >5 m)2 in 68% of the

sampled pastures. Sitona larvae were less abundant in

New York and Vermont. Elaterid larvae comprised a

complex of seven species of which Aeolus melillus (Say)

and Melanotus communis (Gyllenhal) comprised 35%

and 39%, respectively, of the elaterids collected in

Pennsylvania. Agriotes mancus (Say) and Ctenicera

destructor (Brown) comprised 41% and 26%, respec-

tively, of four species collected in New York and

Vermont. Scarabaeid larvae, comprising a complex of

eight species, were detected at only 27% of the seventy-

eight pastures sampled in spring 1994 in Pennsylvania.

Five species were collected in ten of the twelve New

York pastures and four species in nine of the twelve

Vermont pastures. Populations of scarabaeid larvae

averaged <25 m)2 in all three states, except in three

Pennsylvania pastures in spring 1994. Detrended

canonical correspondence analysis (DCCA) showed

pasture standing biomass, legume diversity, pre-winter

stubble height, white clover pasture content, and soil

phosphorus levels in¯uenced numbers of invertebrate

species more than climatic factors, such as temperature,

rainfall, altitude, latitude and seasonal water table.

DCCA also showed most pastures to be close to the

average of environmental factors. The extremely low

density of herbivorous macro-invertebrates in soil and

the absence of pest outbreaks may indicate a stable soil

ecosystem.

Introduction

Grazing pastures for dairy production instead of cutting

them by machines has become rare since the 1930s in

the north-eastern US because farming methods and

associated research have emphasized forage production

for mechanical harvesting and feeding to housed

animals (Fales et al., 1993). Consequently, little is

known of the invertebrate fauna of grazed pastures in

Correspondence to: Dr R. A. Byers, USDA-ARS, Pasture

Systems and Watershed Management Research Unit,

3702 Curtin Road, University Park, PA 16802±3702, USA.

E-mail: [email protected]

Received 26 July 1999; revised 22 November 1999

Ó 2000 Blackwell Science Ltd. Grass and Forage Science, 55, 253±270 253

the region. Literature of the 1930s and 1940s (e.g. Fluke

et al., 1932; Osborn, 1939) is not relevant, especially to

intensively managed pastures of the farms of today,

because the swards that existed 50±60 years ago were a

more biologically diverse, less productive systems.

Insects and other invertebrates are intrinsic compo-

nents of pasture ecosystems. The estimate that the

biomass of these animals, of which >70±98% occurs

below ground (Curry, 1994), often exceeds that of

domestic livestock (Blocker, 1969) and is indicative of

the energy they consume. Indeed 40±90% of net

primary productivity occurs below ground and a high

proportion of this is consumed by soil-dwelling inver-

tebrate herbivores (Scott et al., 1979; East et al., 1981;

Blackshaw, 1984). Thus, herbivorous invertebrates in

pastoral land are often viewed as pests because they

reduce forage available to livestock.

Soil macro-faunal communities play a key role in the

ecology of the soil system (Curry, 1987; 1989; Stork and

Eggleton, 1992; Bond, 1994; Wardle et al., 1999). Their

diversity and distribution among functional groups is

highly relevant to the development of major soil

processes such as litter decomposition and mineraliza-

tion. Thus, any management regime that modi®es the

community structure of soil macro-invertebrates is

likely to have important effects on processes that

ultimately regulate the provision of forage for livestock.

In the past 10±15 years, increasing concern about the

negative environmental effects of con®nement feeding

(Lanyon and Beegle, 1989), rising costs for machinery

and housing, and reduced pro®t margins for milk

production (Hastings, 1987; Ford, 1996) have led to a

renewed interest in lower-input, pasture-based systems

for dairy farms in the north-eastern USA. Pastures were

once located primarily on less tillable soils (Baylor and

Vough, 1985) and managed with low intensity. Now

there is increasing conversion of arable cropping land to

pastures and management-intensive grazing pro-

grammes imposed. Studies elsewhere in the world have

demonstrated clearly that differences in management

practices, such as grazing intensity and levels of fertil-

izer application, have profound effects on the inverteb-

rate fauna of temperate pastures (e.g. Curry, 1994;

Tscharntke and Greiler, 1995). Information is presently

not available to forecast the nature and consequences of

changes in the soil faunas of north-eastern USA

pastures associated with adoption of intensive grazing

programmes. We collected data on soil-dwelling macro-

invertebrates as part of a larger study on the ecosystem

level changes associated with implementation of man-

agement-intensive grazing by dairy cattle on pastoral

land in Pennsylvania, New York and Vermont. Our

principal objectives were: (i) to estimate the relative

contributions of environment and farm management

regimes in in¯uencing community assemblage and

abundance of these soil invertebrates; and (ii) identify

species that potentially may affect sustainability of

intensive grazing systems.

Materials and methods

Survey sites

Twenty-one dairy farms, on which rotational grazing

of milking cows was practised during the pasture

growing season, were selected to provide coverage

of the physio-geographical regions of Pennsylvania.

Within each farm, one to ®ve pastures were selected

depending on the amount of topographic variation, to

provide a total sample size of seventy-eight pastures.

In 1997, three farms in New York and three farms in

Vermont with four pastures per farm were chosen to

provide twenty-four additional pastures (Figure 1 and

Table 1).

Invertebrate sampling

Each pasture in Pennsylvania was sampled for soil-

dwelling macro-invertebrates in spring (late May or

early June) in 1994. A ®ve-farm subset of twenty

pastures, four each on farms 2, 8, 13, 15, and 18, were

further sampled in the same manner in July (summer)

and September (autumn) 1994; May, July and Sep-

tember 1995; and May, July and September 1996.

Pastures in the New York farms were sampled in May,

July and September 1997; and pastures in the Vermont

farms were sampled in June and August 1997. On each

sampling occasion, four soil cores, 10 cm diameter to

10 cm depth, were taken with a golf course cup maker

at each of six locations at 30±100-m intervals along a

transect across the pasture to give a total sample size of

twenty-four cores per pasture. The six locations in a

pasture were near the site of pitfall traps used in a study

of surface dwelling insects, which will be reported in

another publication. These cores were processed in the

®eld by hand crumbling and sorting on a tray. Macro-

fauna were identi®ed to recognizable taxonomic units

and counted. Voucher specimens were collected and

preserved in 70% alcohol for subsequent identi®cation

to species or species groups by the authors and other

specialists. Earthworms were counted but their species

identity was not determined.

Collection of environmental information

Most of the environmental information was intended

for the spring 1994 sampling of the seventy-eight

pastures. Data on age of the pasture (years), duration

of grazing (years), stocking rate (cows ha)1 of pasture),

height of the stubble at the beginning of the previous

254 R. A. Byers and G. M. Barker

Ó 2000 Blackwell Science Ltd, Grass and Forage Science, 55, 253±270

winter, and fertilizer and lime application histories were

obtained from the farm manager or owner. Altitude was

estimated from topographical maps. Daily maximum,

minimum and mean air temperatures, and total rainfall

for each of the 48 months preceding the study were

obtained from the National Weather Service, for mete-

orological stations located nearest the sampling sites.

Soil physical information was taken from soil surveys

published by the US Department of Agriculture (1963;

1968; 1970; 1975; 1978; 1981a;b;c;d; 1982a;b; 1983;

1985a;b; 1986). Data on pH, nutrient status (Olsen P,

exchangeable Ca, exchangeable K, cation exchange

capacity), moisture content (weight loss upon drying at

105°C for 24 h), total organic N and C, and microbial

respiration, were determined for soil samples collected

to 10 cm depth in spring 1994. Basal respiration was

determined for 15 g (wet weight) subsamples incubated

at 22°C in airtight containers. The total CO2-C released

(qCO2-C g)1 soil h)1) between 1 and 5 h into the

headspace of each container was measured by injecting

1-mL subsamples into an infrared gas analyser. Sub-

strate-induced respiration (SIR) was determined as for

basal respiration but amended with 15 000 lg g)1

glucose, according to Wardle and Parkinson (1990).

The microbial metabolic quotient (qCO2) was calculated

from the ratio of basal respiration: SIR as a relative

measure of microbial ef®ciency (Anderson and Domsch,

1985; Wardle, 1993).

To provide estimates of the botanical composition of

the pasture, during spring 1994, herbage was cut to a

height of 25 mm above ground from four

300 ´ 300 mm quadrats about 1 m apart and bulked

for each of six locations within each pasture. On return

to the laboratory, these herbage samples were separated

by species for forage grasses (up to fourteen species) and

legumes (three to four species) and into an aggregated

category for weeds (seventeen species), dried at 140°Cfor 24 h and then weighed. These data were expressed

as standing herbage biomass, percentage composition

by dry weight for each separate component, and

diversity of both grass and legume components calcu-

lated as the Shannon±Weaver function, H¢ (Shannon

and Weaver, 1949).

Statistical analysis

Data on richness and abundance for invertebrates

sampled at the seventy-eight pasture sites in spring

1994 were subjected to analysis of variance (ANOVAANOVA)

to examine inter- and intra-farm differences. These

types of data from the seasonal sampling of the ®ve-

farm subset were examined by ANOVAANOVA for farm, year,

and seasonal effects. Data for the New York and

Vermont farms were also examined by ANOVAANOVA for

between- and within-farm (pasture) effects. Abun-

dance of invertebrates in twenty-four cores per pasture

Figure 1 Map of Pennsylvania, New

York and Vermont, north-eastern USA,

showing location of the dairy farms on

which pastures were sampled for soil

invertebrates. All pastures in Pennsylvania

were sampled in spring 1994, while pas-

tures on ®ve farms ± 2, 8, 13, 15 and 18

(underlined), were also sampled seasonally

in 1994, 1995 and 1996. Pastures on farms

in New York and Vermont were sampled

seasonally in 1997. (See Table 1 for further

details).

Soil invertebrates in pastures 255


was expressed as numbers per m2, with data subjected

to natural logarithmic transformation (Ln + 1) prior to

analysis. Richness was expressed as the number of

species or species groups per pasture. Diversity was

expressed as the product of abundance and richness,

employing the Shannon±Weaver function, H¢. Data

analyses were performed using the SYSTATSYSTAT statistical

package (Wilkinson, 1992).

Discrimination of pastures according to attributes of

the ¯ora recorded for the seventy-eight pastures in

spring 1994 was examined by the polythetic divisive

technique of indicator species analysis (ISA) (Hill

et al., 1975), as implemented in the Cornell ecology

program TWINSPANTWINSPAN (Hill, 1979). Data were input as

the percentage of species of the standing herbage

biomass and the analysis performed on abundance

classes of 0, 1, 2, 3, 5 and 10 as cut points.

Dendrograms showing relationships of the identi®ed

pasture groups were generated as primary outputs,

with indicator species for each level of division in the

classi®cation. Differences among the groups identi®ed

by ISA in ¯oral and environmental attributes and

macro-invertebrate abundance were determined using

ANOVAANOVA.

The data for spring 1994 for invertebrates were

subjected to detrended canonical correspondence ana-

lysis (DCCA) using the CANOCOCANOCO program (Ter Braak,

1986; 1987) to examine broad-scale relationships

between the assemblage of the invertebrate species

and environmental variables of the pasture site, includ-

ing those relating to on-farm management. The envi-

ronmental variables evaluated in DCCA are listed in

Appendices 1 and 2. Natural logarithm transformation

of the invertebrate data was employed and several

CANOCOCANOCO runs were carried out to optimize the choice of

environmental variables, with `stepwise' DCCA to select

the most important variables for the ®nal analysis.

CANOCOCANOCO's Monte Carlo permutation routines were

used for signi®cance testing of relationships between

invertebrate assemblages and environmental/manage-

ment variables. In each permutation, the environmen-

tal variables were assigned randomly to the sites and the

Table 1 Location and some attributes of dairy pastures in Pennsylvania (PA), New York (NY) and Vermont (VT) sampled for soil

invertebrates. (See also Figure 1).

Farm

Pasture

site

number

County

and

State

Pasture

age

(Years)

Grazing

period

(Years)

Stocking rates

(Cows ha)1 d)1 for

each grazing event) Soil series

1 1±5 Lancaster, PA 35 5 76 Genely

2 6±9 Berks, PA 1 1 152 Weikert

3 10±13 Berks, PA 4 4 127 Berks

4 14±17 Lehigh, PA 20 3 89 Trexler, Montevallo

5 18±19 Schuylkill, PA 25 20 64±95 Harleton

6 20 Monroe, PA 150 125 13 Valousia-Lordstown

7 21±23 Luzerne, PA 35 8 89 Lackawanna

8 24±28 Tioga, PA 4±14 4±14 114 Oguaga, Valousia

9 29±32 Tioga, PA 7 7 44 Valousia

10 33±36 Bradford, PA 5 5 76 Valousia, Mardin

11 37±40 Huntingdon, PA 17 11 140 Hagerstown

12 41±44 Mif¯in, PA 3±100 3 152 Hagerstown

13 45±48 Juniata, PA 3±13 3±13 38±51 Edom

14 49±50 Warren, PA 4±16 4±16 28 Venango

15 51±54 Venango, PA 2 2 64 Wharton, Brinkerton

17 59±62 Lawrence, PA 2 2 102 Can®eld, Ravenna

18 63±66 Westmoreland, PA 20 9 68 Upshur-Gilpin, Weikert

19 67±70 Westmoreland, PA 6 6 127 Gilpin

20 71±74 Somerset, PA 9 9 178 Cavode, Rayne-Gilpin

21 75±78 Somerset, PA 7±15 7 89±178 Rayne-Gilpin, Ernest, Atkinson

22 79±82 Chemung, NY 30 30 55±60 Nardin, Valois

23 83±86 Tompkins, NY 9 9 45±50 Howard

25 87±90 Grand Isle, VT 5 5 65 Benson

26 91±94 Franklin, VT 1±10 1±10 50 Marlow

27 95±98 Washington, VT 10 10 20 Cabot

28 99±101 Chenango, NY 9 9 100±120 Valusia



sites ordinated, resulting in a distribution of randomly

generated eigenvalues for comparison with those from

the actual data. In each case, ninety-nine permutations

were performed, allowing P � 0á01 resolution.

Based on the results of the DCCA analysis, scatter

plots and polynomial regression analyses were then

used to explore the relationships between abundance in

selected invertebrate species and environmental vari-

ables using SYSTATSYSTAT.

Results

The macro-invertebrates recorded from the soil samples

are listed in Table 2. Sampling across the seventy-eight

pasture sites in spring 1994 produced richness estimates

that ranged from two to twelve species per pasture site

(mean 6á44 � 0á28). Species richness (F � 4á55;

d.f. � 20, 53; P < 0á01) and diversity (F � 4á55;

d.f. � 20, 53; P < 0á01) varied between farms but not

between pastures within farms (F � 1á80 and 1á22

respectively; d.f. � 4, 53; P > 0á05). Diversity increased

with stocking rate (H¢ � 0á926 + 0á0067 cows ha)1;

R2 � 18á4; P < 0á001).

Sampling across New York and Vermont pastures in

1997 produced richness estimates that ranged from

®ve to eighteen species per pasture site (mean

10á7 � 0á9 s.e.). Species richness (F � 7á05; d.f. � 5,

15; P < 0á01) and diversity (F � 3á54; d.f. � 5, 15;

P � 0á03) varied between farms but not between

pastures within farms (F � 1á46 and 0á69, respectively;

d.f. � 3, 15; P > 0á05).

Earthworms

Sampling in the seventy-eight pastures in spring 1994

revealed that lumbricid earthworms varied in abun-

dance from 0 to 583 m)2, with a mean of 132 m)2.

There was marked variation between farms in earth-

worm abundance (F � 6á57; d.f. � 20, 57; P < 0á001)

but little apparent variation in their abundance

between pastures within farms (F � 1á46; d.f. � 4, 53;

P > 0á05). When present, earthworms generally were

the numerically dominant faunal group. Analysis of the

data from the ®ve-farm subset sampled seasonally over

3 years indicated strong interactive effects of farm, year

and season on earthworm abundance. Again, no

between-pasture variation within farms could be

detected (F � 0á94; d.f. � 3, 160; P > 0á05).

Analysis of data from New York farms indicated strong

interactive effects of farm (F � 23á02; d.f. � 2, 60;

P < 0á01) and season (F � 65á13; d.f. � 2, 60; P < 0á01)

for earthworm abundance. Between pasture variation

was also detected (F � 2á35; d.f. � 9, 60; P � 0á02).

Analysis of data from Vermont sampled seasonally for

earthworms indicated interactive effects for farm

(F � 23á11; d.f. � 2, 60; P < 0á01) but not for season

(F � 0á28; d.f. � 1, 60; P � 0á60). However, between

pasture variance was detected (F � 6á01; d.f. � 9, 60;

P < 0á01).

Potential pest species

Of taxa recognized as potential pests in pasture, elaterid

larvae, Sitona larvae, and scarabaeid larvae were most

widespread and abundant during the sampling in spring

1994 across Pennsylvania.

Elaterid larvae

Elaterid larvae comprised a complex of seven species

(Table 2), of which Aeolus mellitus (Say) and Melanotus

communis (Gyllenhal) comprised 35% and 39% of

macro-fauna individuals collected respectively. Collec-

tively, elaterid larvae ranged in abundance at individual

pasture sites from 0 to 48 m)2 (mean 7á5 m)2). Their

abundance varied signi®cantly between farms

(F � 4á58; d.f. � 20, 57; P < 0á001) but could not be

shown to vary between pastures within farms

(F � 3á09; d.f. � 1, 56; P > 0á05).

Sampling on the ®ve-farm subset over 3 years further

indicated differences in the abundance of elaterid larvae

between farms (F � 11á85; d.f. � 4, 168; P < 0á001), but

less variation between pastures within farms (F � 0á85;

d.f. � 3, 168; P > 0á05), between years (F � 1á69;

d.f. � 2, 168; P > 0á05), and between seasons

(F � 0á15; d.f. � 2, 168; P > 0á05). All seven elaterid

species were represented in soil samples taken in spring,

summer and autumn. Farm mean abundance in elate-

rid larvae was as follows: farm 2, 1á9; farm 8, 5á2; farm

13, 1á3; farm 15, 5á7; farm 18, 10á0 m)2 (pooled s.e.

1á02).

Four species of elaterid larvae, A. mellitus (Say),

M. communis (Gyllenhal), Ctenicera destructor (Brown)

and Agriotes mancus (Say) were found in New York and

Vermont soils. A. mancus and C. destructor comprised

41% and 26% of the total (ninety individuals) respect-

ively. Their abundance at pasture sites ranged from 0 to

61á7 m)2 for New York (mean 9á57 � 1á16 m)2) to 0±

185á1 m)2 (mean 4á49 � 1á60 m)2) for Vermont. Their

abundance in New York did not vary signi®cantly

between farms (F � 0á78; d.f. � 1, 60; P � 0á46) but

varied signi®cantly between paddocks (F � 2á72;

d.f. � 9, 60; P < 0á01).

Abundance of elaterid larvae in Vermont did not vary

between farms (F � 1á95; d.f. � 2, 60; P � 0á15) or

between paddocks within farms (F � 1á12; d.f. � 9, 60;

P � 0á36), but varied signi®cantly between seasons

(F � 5á48; d.f. � 1, 60; P � 0á02). There were over six

times more elaterid larvae collected in the spring than

in summer.



Table 2 Soil-dwelling macro-invertebrates recorded in Pennsylvania, New York and Vermont dairy pastures.

Class Order Family Genus species

Code used in the ordination

diagram (Figure 2)

Annelida Clitellata Lumbricidae Four unidenti®ed species Lum

Mollusca Stylommatophora Succineidae Succinea putris (Linnaeus) Sup

Cochlicopidae Cochlicopa lubrica (MuÈ ller) Col

Valloniidae Vallonia pulchella (MuÈ ller) Vae

Agriolimacidae Deroceras reticulatum (MuÈ ller) Der

Deroceras laeve (MuÈ ller)

Arionidae Arion fasciatus Nilsson Arf

Crustacea Isopoda Porcellionidae Tracheoniscus rathlei Brandt

Chilopoda Geohilomorpha Three unidenti®ed species Cen

Diplopoda Julida One unidenti®ed species Mil

Insecta Thysanura Campodeidae Unidenti®ed sp.

Isoptera Rhinotermitidae Reticulitermites ¯avipes (Kollar)

Dermaptera For®culidae For®cula auricularia (Linnaeus) Foa

Homoptera Cicadidae Tibicen canicularis Harris

Coleoptera Curculionidae Sitona hispidulus (Fabricius) adults ShA

Sitona larvae ShL

Sphenophorus minimus (Hart) adults SpA

Sphenophorus minimus (Hart) larvae SpL

Elateridae Aeolus melillus (Say) adults A1A

Agriotes mancus (Say) larvae AmL

Ctenicera aeripennis destructor (Brown) larvae CdL

Conoderus lividus (DeGeer) larvae

Ctenicera sp.1 larvae

Limonius agonus (Say) larvae LaL

Melanotus communis (Gyllenhal) larvae MeL

Aeolus amabilis (LeConte) adults A2A

Alaus occulatus (Linnaeus) adults

Limonium sp.1 adults L1A

Melanotus sp.1 adults M1A

Melanotus sp.2 adults M2A

Elateridae sp.1 adults E1A

Elateridae sp.2 adults E2A

Scarabaeidae Anomala innuba (Fabricius) larvae

Cyclocephala immaculata Olivier larvae CiL

Diplotaxis sp. larvae

Maladera castanea (Arrow) larvae McL

Onthophagus hectate (Panzer) larvae

Phobetus comatus sloopi Barrett larvae

Rhizotrogus (Amphimallon) majalis

(Razoumowsky) larvae

Phyllophaga spp. larvae P1L

Phyllophaga hirticula (Knoch) larvae

Popillia japonica Newman larvae PjL

Aphodius granarius (Linnaeus) adults A3A

Aphodius erraticus (Linnaeus) adults A4A

Aphodius ®metarius (Linnaeus) adults

Ataenius strigatus (Say) adults

Onthophagous taurus (Schreber) adults



Table 2 (Continued).

Class Order Family Genus species

Code used in the ordination

diagram (Figure 2)

Carabidae Pterostichus sp. larvae

Agonum muelleri (Herbst) adults

Agonum punctiforme (Say) adults

Amara aenea (DeGeer) adults AaA

Anisodactylus sanctaecrucis (Fabricius) adults

Anisodactylus rusticus (Say) adults ArA

Bembidion mimus Hayward adults

Bembidion obtusum Serville adults

Bembidion quadrimaculatum oppositum

Say adults

Bembidion rapidum (Le Conte) adults

Bradycellus ruprestris (Say) adults

Cyclotrachelus sodalis (Le Conte) adults

Harpalus herbivagus Say adults

Harpalus af®nis (Schrank) adults HaA

Harpalus fulgens Csiki adults HfA

Omophron tesselatus Say adults

Poecilus chalcites (Say) adults

Poecilus lucublandus (Say) adults PlA

Pterostichus corvinus (Dejean) adults

Staphylinidae Staphylinidae sp.1 larvae S1L

Staphylinidae sp.2 larvae S2L

Astenus sp. adults

Lathrobium pallidum (Le Conte) adults

Neohypnus obscurus Erichson adults NoA

Philonthus cognatus Stephens adults PcA

Philonthus varius-carbonarius (Gravenhorst)

adults

PvA

Platydracus mysticus Erichson adults

Platystethus sp. adults

PlamysA

Cantharidae Chauliognathus pennsylvanicus (De Geer)

adults

C1A

Cantharidae sp.1 adults C2A

Cantharus sp.1 larvae C1L

Cantharus sp.2 larvae C2L

Lampyridae Photoris pensylvanicus De Geer adults

Lampyridae sp. 1 larvae

Meloidae Meloidae sp. 1 larvae M1L

Diptera Stratiomyiidae Stratiomyiidae sp. 1 larvae S3L

Tipulidae Limonia sp. 1 larvae L1L

Tipula sp.1 larvae T1L

Tipula sp.2 larvae T2L

Tabanidae Tabanus spp. larvae T3L

Lepidoptera Noctuidae Spodoptera frugiperda (J.E. Smith) larvae

Noctuidae sp. 1 larvae N1L



Sitona larvae

Analysis of data from Sitona larvae were recorded at

nineteen of the twenty-one farms sampled in spring

1994 and occurred at detectable population levels

(>5 m)2) in 68% of the sampled pastures. Populations

ranged from 0 to 138 m)2 (mean 16á5 m)2). Only in

three pastures did Sitona larvae approach population

levels that may be regarded as pest potential: pasture 1,

138 m)2; pasture 2, 111 m)2; and pasture 64, 101 m)2.

Abundance of Sitona larvae varied between farms

(F � 4á09; d.f. � 20, 57; P < 0á001), but not between

pastures within farms (F � 0á68; d.f. � 1, 56; P > 0á05).

Analysis of the data from the ®ve-farm subset sampled

seasonally over 3 years indicated strong interactive

effects of farm, year and season on Sitona larval

abundance. Larvae occurred in soil almost exclusively

in spring and were more abundant in 1994 than in the

following 2 years. Variation in abundance within farms

could not be detected (F � 0á73; d.f. � 3, 168; P > 0á05).

Sitona larvae were recorded at all three farms in New

York but in only ®ve of twelve pastures at populations

of 0±30á9 m2 (mean 0á86 � 0á34 m)2). Abundance of

Sitona larvae did not vary signi®cantly between farms

(F � 0á51; d.f. � 2, 60; P � 0á60) or between paddocks

within farms (F � 1á01; d.f. � 9, 60; P � 0á43). Sitona

larvae were recorded at all three farms in Vermont, but

in only six of twelve pastures at populations of 0±

61á7 m)2 (mean of 2á14 � 0á72 m)2). Abundance of

Sitona larvae did not vary between farms or between

paddocks within farms (F � 1á81; d.f. � 2, 60; P � 0á17;

F � 0á80; d.f. � 9, 60; P � 0á59 respectively). However,

abundance of Sitona larvae varied between seasons

(F � 5á84; d.f. � 1, 60; P � 0á02) (3á8 m)2 in spring and

0á4 m)2 in summer).

Scarabaeid larvae

Scarabaeid larvae, comprising a complex of eight species

(Table 2), were detected in only 27% of the seventy-

eight pastures sampled in spring 1994. Populations

ranged from 0 to 53 m)2 (mean 4á2 m)2) with signi®-

cant variation between farms (F � 2á96; d.f. � 20, 56;

P < 0á001). Within-farm (F � 3á65; d.f. � 1, 56;

P > 0á05) differences in scarabaeid larval abundance

could not be detected. Phyllophaga spp. were most

frequently encountered. Only in three pastures were

the populations considered of potential pest status

(pasture 20, 26á5 m)2; pasture 55, 53á0 m)2; pasture

62, 26á5 m)2): in each case these populations comprised

only Phyllophaga spp.

Scarabaeid larval assemblages on the ®ve-farm subset

ranged from one to six species. Abundance tended to be

highest for pastures on farm 18, where Anomala innuba

(Fabricius) dominated a complex of six species, in

samples from 1994, and in samples taken in autumn.

However, abundances were subject to interactive effects

of farm, year and season. Scarabaeid larval abundance

could not be shown to vary between pastures within

farms (F � 0á32; d.f. � 3, 168; P > 0á05).

Five species of scarabaeid larvae, Maladera castanea

(Arrow), Popillia japonica Newman, A. innuba, Cyclocep-

hala immaculata Olivier, and Rhizotrogus majalis (Razou-

mowsky), were collected in ten of the twelve New York

pastures. Populations ranged from 0 to 185á2 m)2

(mean 11á7 � 1á8 m)2) with signi®cant variation

between farms (F � 15á51; d.f. � 2, 60; P < 0á01).

Within-farm differences in the abundance of scarabaeid

larvae could not be detected (F � 1á10; d.f. � 9, 60;

P � 0á37). P. japonica larvae were most frequently

encountered.

Four species of scarabaeid larvae, Phyllophaga hirticula

(Knoch), P. japonica, C. immaculata, and R. majalis, were

collected in nine of the twelve Vermont pastures at

populations ranging from 0 to 92á6 m)2 (mean

3á64 � 0á98) with no signi®cant difference between

farms (F � 0á50; d.f. � 2, 60; P � 0á61). There were no

signi®cant differences (F � 1á84; d.f. � 9, 60; P � 0á08)

for pastures within farms. C. immaculata was the species

most frequently encountered.

Patterns of community composition

The results of DCCA of the spring 1994 sampling at

seventy-eight pasture sites are presented as an ordina-

tion diagram in Figure 2 (eigenvalues: axis 1 � 0á402,

axis 2 � 0á264). The species and site points jointly

represent the dominant patterns in community compo-

sition in environmental space. By reference to the

species-environmental variables interset correlation co-

ef®cients (Table 3) and the DCCA ordination diagrams, it

was evident that the recorded environmental variables

most strongly associated with axis 1 were geographical

position as estimated from altitude, temperature, rain-

fall, soil ®ne particle content, soil seasonal water table,

soil moisture content, soil exchangeable potassium

content, soil SIR/C ratio, pasture legume and grass

species diversity, and pasture content of Trifolium repens.

In axis 2, the dominant variables were stocking rate,

temperature, rainfall, soil moisture content, soil phos-

phorus content, soil basal respiration rate, pasture

standing biomass, and pasture grass species diversity.

Because each site point lies at the centroid of the

species points that occur at that site, one may infer from

the ordination species that are likely to be present at a

particular site. Also, in so far as canonical correspon-

dence analysis is a good approximation to the ®tting of

Gaussian response surfaces, the species points are

approximately the optima of these surfaces; hence the

abundance or probability of occurrence of a species



Figure 2 Detrended canonical correspondence analysis of soil dwelling macro-invertebrate assemblages in seventy-eight

Pennsylvania (PA) dairy pastures sampled in spring 1994. (a) Pasture site ordination (see Table 1 for pasture site identi®cation and

description), with dominant environmental gradients overlaid as vectors (arrows) and centroids h. (b) Invertebrate species

ordination (See Table 2 for species codes). Gradients of axes 1 and 2 are signi®cant (P < 0á05) according to a Monte Carlo

permutation test (see Materials and methods). Soil SIR/C, Soil substrate-induced respiration/carbon ratio.



decreases with distance from its location in the ordina-

tion diagram. The environmental variables accounted

for 49% of the variance in the weighted averages of the

®fty-seven invertebrate species (species groups) included

in the ordination. However, for the most part, the

placement of individual species in the ordination was

not robust, due to the low numbers of these macro-

invertebrates in the soil samples.

Earthworms (an aggregate of several lumbricid spe-

cies) were placed at no great distance from the origin of

the ordination diagram (Figure 2B). The high percen-

tage of variance accounted for (57% and 19% for axes 1

and 2 respectively) indicates that placement in the

ordination space genuinely re¯ects habitat optima of

these animals. Regression analyses indicated a negative

association of earthworm abundance with the stock-

ing rate (earthworms m)2 � 255á9 ± 1á202 cows ha)1;

r2 � 0á136; P < 0á01). Earthworm abundance was pos-

itively related to soil moisture content (Ln + 1 earth-

worms m)2 � 2á118 + 0á082% soil moisture content;

r2 � 0á276; P < 0á001). While soil qCO2 was not

signi®cantly correlated with the ordination axes, scatter

plot evaluation and regression analysis indicated re-

striction of high earthworm abundance to sites of low

microbial metabolic quotient [Ln + 1 earthworms

m)2 � 3á483 + 0á085 (1/qCO2); r2 � 0á088; P < 0á01].

Sixty-three per cent of the variance in Sitona larval

abundance was accounted for in axis 1 of the DCCA

ordination, consistent with the gradient for pasture

content of T. repens L., one of the primary host plants of

Sitona. However, scatter plot and regression analyses

failed to detect any association between Sitona larval

abundance and the environmental variables aligned with

axis 1. Axes 1 and 2 together accounted for less than 5%

of the variance in Sitona hispidulus adult abundance.

Sphenophorus larvae were strongly aligned to axis 2 in the

ordination,with52%ofvarianceinabundanceaccounted

for. The placement near the origin of the ordination

adult Sphenophorus minimus (Hart) and S. parvulus

Gyllenhal and the low proportion of variance explained

indicated that their habitat optima were not perfectly

de®ned by the sites included in our sample.

For the elaterids recorded in the samples, habitat

optima were not well de®ned. Ctenicera aeripennis

destructor (Brown) larvae were aligned with axis 1 of

the DCCA ordination, but with 9% variance in abun-

dance explained by the linear combination of environ-

mental variables input into DCCA. Likewise, A. mancus

(Say) larvae were aligned with axis 2, with 18% of

variance explained.

The larvae of the scarabaeids M. castanea (Arrow), and

Phyllophaga spp. were placed near the origin of the

DCCA ordination and the low proportion of variance

accounted for indicated that their habitat optima were

not perfectly de®ned by our sample set. The larval

stages of the dynastine C. immaculata Olivier and the

ruteline P. japonica Newman were most strongly aligned

with axis 1 and 2, respectively, but again only a low

proportion of variance in their abundance was accounted

for (14% and 6%) in the ordination.

Pearson's correlation coef®cients

Axis 1 Axis 2

Pasture age )0á014 )0á100

Stocking rate 0162 0á264

Nitrogen fertilizer usage 0á142 )0á031

Phosphorus and potassium fertilizer usage 0á053 )0á030

Altitude )0á297 )0á041

Mean monthly maximum temperature 0á350 )0á261

Mean monthly minimum temperature 0á310 )0á071

Annual rainfall 0á257 )0á255

Soil <200 l particle content )0á353 )0á186

Soil seasonal water table )0á443 )0á118

Soil moisture content )0á280 )0á307

Soil phosphorus content )0á020 0á326

Soil exchangeable potassium content 0á345 0á207

Soil substrate induced respiration/carbon ratio )0á223 0á032

Soil basal respiration rate )0á076 0á295

Pasture standing biomass 0á186 0á247

Pasture legume species diversity 0á345 0á085

Pasture grass species diversity )0á279 )0á250

Pasture Trifolium repens content 0á366 )0á065

Values in bold signi®cant at P < 0á05.

Table 3 Interset correlations of

environmental variables with axes one and

two in a detrended canonical

correspondence analysis for soil-dwelling

macro-invertebrate assemblages in grazed

Pennsylvania dairy pastures.



Of the predatory macro-fauna, comprising primarily

of centipedes, Carabidae and Staphylinidae, only the

adult stage of the staphylinid Neohypnus obscurus Erich-

son was robustly placed in the ordination, with 18% of

variation in abundance accounted for in axis 2. Axis 3

explained 46% of the variance in abundance of milli-

pedes, a likely important macro-fauna element of the

detritivore guild.

Indicator species analysis

Fourteen pasture groups were recognized from the ISA

of the ¯oral data (Figure 3). While many of the pasture

sites on a particular farm were grouped together, there

were numerous exceptions. Indeed, pastures from

geographically dispersed farms were frequently classi-

®ed as having similar ¯oral assemblages. ANOVAANOVA indi-

cated signi®cant differences between the fourteen

pasture groups in grass and legume contributions, and

in seven of the environmental variables that correlated

with axes 1 and 2 in the DCCA ordination (Table 4)

(These results will be discussed in more detail in a

subsequent paper). There were no signi®cant differences

in soil macro-invertebrate species richness or diversity

between these ISA pasture groups (data not presented)

but abundance of some invertebrate species did vary

among pasture groups (Table 5).

Discussion

The low species richness in macro-invertebrates, dom-

inated at most sites by earthworms, found in this study

is typical of managed temperate grassland soils (Peter-

sen, 1982; Curry, 1989). Earthworms are recognized as

being important in maintaining soil fertility and struc-

ture (e.g. Waters, 1951; Edwards and Lofty, 1972; Syers

and Springett, 1983; Curry, 1989) and their presence

has been demonstrated to have bene®cial impacts on

grassland productivity (Stockdill and Cossens, 1966;

Edwards and Lofty, 1980; Curry and Boyle, 1987). They

Figure 3 Dendrogram showing rela-

tionships between the fourteen pasture

groups identi®ed by indicator species

analysis of the ¯oral data, with indicator

species (abundance class in parenthesis)

for each division.



are also important in reducing surface run-off of soluble

P and N (Sharpley et al., 1979). In the present study, a

number of dairy pastures were identi®ed as having few

earthworms, with the variation occurring at the farm

level rather than between pastures within farm. For

longer sustainability of intensive grazing, it may be

Table 4 Floral and environmental attributes of fourteen pasture groups identi®ed by indicator species analysis of ¯oral composition

of seventy-eight Pennsylvania dairy pastures sampled in spring 1994. Results from ANOVAANOVA and mean values are given for each

continuous site factor that was signi®cantly correlated with axes one and two in detrended canonical correspondence analysis and

differed between groups.

T W I N S P A NT W I N S P A N group 1 2 3 4 5 6 7 8 9 10 11 12 13 14

F-value

signi®cance

Grasses, percent of

biomass

63 77 65 65 76 71 68 68 80 82 76 58 70 37 2á80**

Legumes, percent

of biomass

28 17 19 16 7 16 27 22 8 5 11 32 18 54 5á59***

Grass species

richness

(no. of species)

6á5 5á8 5á1 5á2 7á1 6á6 6á0 5á3 7á3 6á0 5á0 6á3 4á0 3á5 2á95**

Grass species

diversity (H¢)1á8 1á6 1á6 1á5 2á1 1á9 1á7 1á4 2á2 1á7 1á4 2á1 0á5 1á2 3á49***

Legume species

diversity (H¢)0á7 0á3 0á2 0á7 0á8 0á3 0á3 0á4 0á9 0á5 0á2 0á6 0á8 1á5 2á28*

Altitude (m) 396 455 504 372 335 350 284 215 297 278 152 230 151 168 5á42***

Minimum

temperature (°C)

3á5 2á9 2á8 3á6 2á9 3á7 4á6 4á8 3á7 4á9 5á5 4á8 5á0 4á8 4á81***

Slope (degrees

incline)

10 6 16 12 14 11 27 14 20 16 5 10 33 20 2á08*

Soil ®ne particle

content (%)

30 72 71 60 61 65 55 67 45 45 17 60 21 50 2á78**

Soil substrate-

induced

respiration rate

(lg CO2-C g)1 soil h)1)

10á2 8á2 14á2 11á4 13á6 11á1 13á0 6á7 11á2 9á4 6á0 11á5 4á7 5á4 2á66**

Soil water-

holding

capacity (mm)

432 457 432 406 406 458 482 407 305 330 229 405 230 356 3á08***

Stocking rate

(cows ha)1)

127 133 137 91 92 85 71 71 72 96 127 140 131 152 2á66**

Degrees of freedom = 13, 64, * P < 0á05, ** P < 0á01, *** P < 0á001.

Table 5 Abundance (numbers m)2) in selected macro-invertebrates for fourteen pasture groups identi®ed by indicator species

analysis of ¯oral composition of seventy-eight Pennsylvania dairy pastures sampled in Spring 1994.

T W I N S P A NT W I N S PA N group 1 2 3 4 5 6 7 8 9 10 11 12 13 14

F-value

signi®cance

Earthworms 51á5 14á8 11á8 27á6 25á5 23á2 32á7 46á1 17á0 8á12 7á0 31á3 37á3 71á5 2á20*

Sitona larvae 12á5 5á2 3á9 2á6 1á3 2á1 10á0 0á9 6á7 3á2 0á5 2á3 2á0 1á5 3á87***

Elateridae larvae 2á0 0á4 1á2 0á8 1á7 0á8 2á0 1á4 1á7 1á0 2á0 4á3 0á3 4á5 2á60*

Elateridae adults 0á0 0á0 0á4 0á0 0á3 0á0 0á0 0á6 0á0 0á1 0á0 0á0 0á0 0á0 1á03*

Scarabaeidae larvae 0á0 0á2 0á4 1á2 1á3 0á1 0á3 0á6 1á7 0á5 1á5 0á7 1á7 3á5 1á18*

Tipulidae larvae 0á0 1á2 0á8 0á0 0á1 0á0 0á3 0á3 0á7 0á0 0á0 0á0 0á0 0á0 2á42**

Carabidae 0á0 0á2 0á2 1á6 0á3 0á3 0á0 0á1 0á3 0á5 0á5 0á0 0á7 0á0 2á47**

Staphylinidae 0á5 0á2 0á4 1á6 0á2 0á3 0á0 0á1 0á0 0á0 0á0 0á3 0á3 0á0 1á60*

A N O V AA N O VA performed on Ln + 1 transformed data. Degrees of freedom = 13, 64, * P < 0á05, ** P < 0á01, *** P < 0á001.



bene®cial to increase numbers of earthworms at these

sites, either by introduction (Stockdill, 1982; Hoogerk-

amp et al., 1983; Curry and Boyle, 1987) or by soil

amendment to promote population increase.

The DCCA did not provide for clear de®nition of the

habitat optima for the earthworm species complex

present in the sampled Pennsylvania pastures. Regres-

sion analysis, however, clearly indicated high abun-

dance of earthworms to be associated with low stocking

rates and high soil moisture content: these two envi-

ronmental factors were not correlated but constituted

opposing gradients in the DCCA ordination. Laboratory

and ®eld microcosm studies have demonstrated the

signi®cance of the soil fauna in stimulating microbial

activity and release into the soil solution of nutrients

immobilized in microbial biomass (e.g. Anderson et al.,

1983; 1985). For the Pennsylvania pastures in our

study, high abundance of earthworms (200±600 m)2)

was con®ned to soils with low values of the microbial

metabolic quotient, qCO2, which in turn were con®ned

to the higher moisture content of the soils (>30%).

However, low numbers of earthworms (<100 m)2)

were recorded along the full qCO2 gradient (basal

respiration: substrate-induced respiration ratios 0á05±

0á55) and moisture contents (15±49%). In the past,

qCO2 has been used as an index of ecosystem develop-

ment based on Odum's theory of ecosystem succession,

during which it is predicted to decline (increasing

microbial ef®ciency); conversely, during disturbance

qCO2 is predicted to increase (reduced microbial ef®-

ciency) (Anderson and Domsch, 1985; Wardle, 1993).

However, Wardle and Ghani (1995) found that qCO2 is

often insensitive to disturbance and ecosystem devel-

opment, fails to distinguish between effects of distur-

bance and stress, and does not decline predictably in

response to ecosystem development whenever stress

increases along successional gradients. Nonetheless, one

interpretation of our data on qCO2 is that occurrence of

high earthworm abundance in Pennsylvania dairy

pastures is con®ned to undisturbed or low-stress situ-

ations. Many of the sampled Pennsylvania soils are

drought-prone, with low water-holding capacity and

subject to high evaporative demands during summer ±

thus instability in moisture availability may be a key

stress factor, accentuated by disturbance associated

with highly intensive grazing. The sampling on the

®ve-farm subset indicated differences in abundance of

earthworms that occurred between years and seasons

varied with farm, suggesting a farm location or

management factor contributed to the differences in

earthworm populations. The sampling on New York

farms indicated differences in the abundance of

earthworms between seasons, probably re¯ecting low-

er soil moisture conditions in summer. The sampling of

Vermont farms did not detect seasonal differences in

the abundance of earthworms because soil moisture

was more uniform during the year.

While several recognized pest (herbivorous) species

occurred widely, their populations were generally low

and no evidence of damage to the swards was observed.

There are two species of Sitona, S. hispidulus (Fabricius)

and S. ¯avescens (Marsham) in Pennsylvania. We

assumed most of the larvae were S. hispidulus, the

dominant species, but there are no published larval keys

to species. Both species feed on Trifolium spp. but only

S. hispidulus larvae can survive on Medicago sativa (Byers

and Kendall, 1982). Larvae of Sitona were widely

dispersed and of common occurrence in north-eastern

USA dairy pastures, although infrequently at high

abundance. Although S. hispidulus was reported as early

as the 1930s attacking Trifolium in north-eastern USA

(Bigger, 1932), and is of well-known pest status in

M. sativa forage crops (Hower et al., 1993), the status of

this insect has received little attention as a pasture pest

in the region. The position of this species in the DCCA

ordination was consistent with the gradient of its

principal host plant in pastures, namely the legume

T. repens. Our failure to con®rm a relationship between

S. hispidulus and T. repens content in the regression

analyses, and the absence of a consistent association

with the ISA pasture groups of high legume content,

suggests a complex of factors regulating larval abun-

dance in this curculionid species. The seasonal sampling

on the ®ve-farm subset demonstrated marked between-

year variation, and also a farm ´ year interaction in the

variation, in abundance of Sitona larvae; this suggests

the role of both the broad climate pattern and on-farm

management on populations. Furthermore, the abun-

dance of Sitona larvae was very low in the New York

and Vermont pastures, but the pastures may have been

sampled too early in the season to detect the peak

numbers. The importance of Sitona larvae as a pest of T.

repens in dairy pastures in the north-eastern USA,

particularly under intensive grazing, warrants further

investigation.

Scarabaeid larvae are recognized as important pests in

grassland systems in many parts of the world, including

the USA (Ueckert, 1979; Potter, 1982; Watts et al.,

1982; Tashiro, 1987; 1990; Potter and Braman, 1991).

Characteristically they cause acute damage to grassland

turfasaresultof a localandsporadic (oftencyclical)build-

up of populations. Although these insects are generally

versatile in their habits, they may display marked host

plant (e.g. Crutch®eld and Potter, 1994) and habitat

preferences (e.g. Katovich et al., 1998). Scarabaeidae

were generally of infrequent occurrence and low

abundance in our spring 1994 sample of seventy-eight

pastures. Phyllophaga spp. were most frequently

encountered and approached populations that may be

considered of potential pest status in three pastures.



Because of the general low frequency and abundance of

Scarabaeidae in our samples, the DCCA did not allow

for robust assessment of the environmental or manage-

ment factors determining assemblage of these insects in

Pennsylvania dairy pastures, although associations of

P. japonica and C. immaculata with gradients of stocking

rate and pasture legumes, respectively, were indicated.

Future studies should consider the in¯uence of stocking

density on populations of these important macro-

invertebrates.

There is general agreement in the literature that the

complex invertebrate communities characteristic of

unmanaged grasslands are replaced by simpli®ed com-

munities which can tolerate disturbance and which are

adapted to exploit the greater productivity of managed

swards (Andrzejewaka, 1979; Pottinger, 1993). Com-

munities in simple swards are more prone to pest

outbreaks (less stable) than those of mixed vegetation

(Pimentel, 1961; Root, 1973; Pottinger, 1976). Increas-

ing stocking rates generally increases the sensitivity of

grazing systems to losses in herbage production from pest

damage (Kain, 1979). Earthworms are usually most

abundant under conditions of high fertility and intensive

utilization (Curry, 1969, 1976). However, Hutchinson

and King (1980) recorded peak values in abundance and

biomass for earthworms and Scarabaeidae at intermedi-

ate stocking levels. Roberts (1973) has pointed out that

the response to stocking level for any invertebrate group

may be a composite based on separate relationships for

each species; this was illustrated by differences in the

responses of two major root-feeding scarabaeid larvae in

pasture sites grazed at three stocking rates.

Future work with soil macro-invertebrates will focus

on whole farm oriented research utilizing plant species

diversity studies with the overall objective to sustain

productivity. Species richness can be expected to

increase under long-term, undisturbed pasture condi-

tions (Edwards, 1983; Fraser et al., 1996). Rotational

grazing of dairy pastures is likely to become more

intensive in the future as farmers seek to increase pro®ts

by increasing herd size. The increased stocking rates may

lead to pest problems not evident now because most

pastures in the region are underused. The challenge will

be to manage the stocking rate to increase pro®t without

making pastures susceptible to pest outbreaks.

Acknowledgments

We thank the following producers who allowed us to

sample their pastures: J. and K. Beary, W. Chamberlain,

N. and P. Clark, W. Comely, R. Daubert, C. and

B. Dietrich, R. Field, H. and S. Forgues, J. Gebhart,

R.Gilkinson,H.Guyer,W.Harman,B.Hawthorne,L.and

R. Hibbard, J. Hoover, A. Linde, T. Miller, G. Moyer,

T. Murphy, L. Queitzsch, J. Rodgers, M. Smith,

F. Stricker, E. VanTassel, J. Welch, G. Vandeweert and

M. Widman. Thanks are due to A. C. Firth (deceased)

for assistance with DCCA, and D. A. Wardle for the soil

microbial respiration analyses. We are indebted to

R. Davidson for identi®cation of the Carabidae and

R. Hoebeke, for identi®cation of the Staphylinidae

and to B. Pass, G. Baker, B. Barratt, P. Murray and

R. T. Sherwood for reviewing earlier versions of the

manuscript. Finally, we thank J. Everhart, R. Hald-

eman, S. LaMar and numerous students for technical

assistance.

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Appendix 1

Management-related variables used in detrended

canonical correspondence analysis of soil macro-inver-

tebrate assemblages in grazed Pennsylvania dairy

pastures.

Continuous variables

Age of pasture (years) (1±150; mean 16á0 � 2á6)

Stocking rate (Cows ha)1, based on paddock area and number

of cows in herd) (13±178; mean 103á0 � 12á2)

Prewinter sward defoliation height (cm) (25±150; mean

59á2 � 3á7)

Categorical variables

Nitrogen fertilizer applied

Phosphorus and potassium fertilizers applied

Lime applied

Composted manure applied

Appendix 2

Environmental variables used in detrended canonical correspondence analysis of soil-dwelling macro-invertebrate

assemblages in grazed Pennsylvania dairy pastures.

Continuous variables

Latitude (degrees North) (39á50±41á58; mean 40á53 � 6á20)

Longitude (degrees East) (75á17±80á29; mean 77á69 � 17á70)

Altitude (m) (104±610; mean 330á3 � 15á6)

Slope (degree incline) (0±40; mean 14á5 � 1á1)

Mean monthly maximum temp °C (12á7±18á2; mean 15á9 � 0á1)

Mean monthly minimum temp °C (1á2±5á8; mean 3á7 � 0á2)

Average total rainfall (mm) (848á1±1227á1; mean 1026á9 � 13á2)

Distance from nearest forest or substantial shelterbelt/hedgerow (m) (40±1000; mean 384á7 � 42á0)

Soil* content of coarse stone (%) (0 � 46; mean 12á1 � 1á5)

Soil* content of particles passing 200-l mesh (%) (15±87; mean 57á9 � 2á6)

Soil* water holding capacity (mm in pro®le) (228±559; mean 406 � 99)

Soil pH (5á1±7á3; mean 6á55 � 0á06)

Soil phosphorus (Olson P) (7±90; mean 30á5 � 2á0)

Soil total nitrogen (%) (0á1±0á5; mean 0á27 � 0á01)

Soil carbon (%) (2á3±6á9; mean 4á12 � 0á11)

Soil carbon\nitrogen ratio (10á8±26á0; mean 15á9 � 0á3)

Soil basal respiration (lg CO2-C g)1 soil h)1) (0á36±1á92; mean 1á13 � 0á04)

Soil substrate-induced respiration (SIR) (lg CO2-C g)1 soil h)1) (2á32±19á32; mean 10á76 � 0á54)

Soil basal/substrate-induced respiration ratio (qCO2) (0á04±0á53; mean 0á14 � 0á01)

Soil substrate-induced respiration/carbon ratio (0á63±4á42; mean 2á56 � 0á11)

Soil moisture content (% moisture/dry weight) (15á4±48á6; mean 27á16 � 0á92)

Soil exchangeable potassium (milli-equivalents percentage) (0á17±1á40; mean 0á55 � 0á03)

Soil exchangeable magnesium (milli-equivalents percentage) (0á7±3á7; mean 1á81 � 0á06)

Soil exchangeable calcium (milli-equivalents percentage) (2á8±16á8; mean 7á75 � 0á25)

Soil cation exchange capacity (milli-equivalents percentage) (8á7±17á6; mean 12á39 � 0á23)



Categorical variables

Soil* moisture holding capacity (low/high)

Soil* permeability (low/high)

Soil* seasonal water table within 30á3 cm of surface (presence/absence)

Soil* series characterized by hard bedrock (presence/absence)

Soil* series derived from shale (presence/absence)

Soil* series derived from sandstone (presence/absence)

Soil* series derived from limestone (presence/absence)

Soil* series derived from calcareous shale (presence/absence)

* From US Department of Agriculture, Soil Survey publications 1963±86.



soil dwelling macro-invertebrates in intensively grazed dairy pastures in pennsylvania, new york and...

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