forest dynamics note

8/9/2019 Forest Dynamics Note

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FOREST DYNAMICSFOREST DYNAMICS


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Forest is an important biological resources. It has the characteristicsof wide distributions and long growing period. Changes often take

place under the actions of man-made elements and natural

elements.

Promptly and accurately monitoring dynamic changes of forest

resources, mastering the changing regularity of forest resources,have an important social, economic and ecological significance.

Gaps, the result of natural canopy perforation, are the kernels of

forest regeneration of tropical rainforests.

The process of canopy perforation, and hence the formation of

canopy gaps drives the regeneration cycle of the tropical rainforest.


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Canopy gaps constitute small to mid-scaled disturbances created

by the fall of the structural elements of the forest.

In places where gaps are formed, new forest patches start to

regenerate and grow until they eventually reach a stage of maturity,

from which gaps are formed again.

In general, gaps create spatial and temporal habitat heterogeneity,release a free space for tree regeneration, and allow sunlight to

reach the understory.

All of these factors, bound to plant response to gaps influence

forest diversity, structure, and composition.

Gap shape, together with gap area and orientation has been

considered as an additional factor influencing habitat

heterogeneity.


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Gap shape is of crucial importance for the penetration of sunlight to

the understory, hence having a share in the influence of the gap

microclimate.

Gap size, instead of shape and orientation, is more important for

the determination of the general gap light regime. Finally, the height

of the trees that create gaps is the main determinant of gapmorphology, especially gap size.

Gaps in the rainforest are also created anthropogenically (e.g. by

logging). Therefore, the application of gap theory, and the

understanding of the functioning of the forest are very important

and promising issues to be considered in the conservation of

tropical rainforests.


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A PRELIMINARY ASSESSMENT OF FOREST GAPS

CAUSED BY WINDSTORM IN PASOH FOREST

RESERVE, MALAYSIA

By,

Zulhazman Hamzah1, Rongsheng Li2,

NorZaneedarwaty Norman3 & Nor Aznan Mahmood4

Study Case 1


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Gaps are colonized by seedlings, which grow up and become

saplings. Then they transforms into poles before attaining maturity.

Where a tree dies of old age, its crown slowly dies back and then

the limbs and finally the bole disintegrate. In other cases, tree may

die suddenly, struck by lightning or blown over, or snapped off by

wind. Such instances are very rare in tropical rain forest especially

in Malaysia where windstorm blows and creates a huge forest gap.

In Pasoh Forest Reserve (F.R.), Malaysia, a windstorm incidence in

July 2001 created unusually huge forest gaps. Many large-sized

trees were thrown over resulting in gaps which were in the form of

discontinued clearing or pockets.

The sizes of gaps also differ from place to place depending on

velocity and intensity of the windstorm, altitude, canopy tree sizes

and distribution patterns, existence of climbers or lianas and

whether or not tree has buttress or root.


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Class Direct fall Hit by tree Pull by climbers Total %

Emergent 2 0 0 2 1.44

Main canopy 17 3 9 29 19.42

Understorey 9 36 63 108 79.13

Total 28 72 39 139 -

% 20.14 51.80 28.06 - 100.00

Percentage of tree canopy category and tree fall pattern.

Result


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FOREST FILLED WITH GAPSThe effect of gap size on microclimate, water and

nutrient cycling: A study in Guyana.

By:

Oscar van Dam

Summary PhD thesis Utrecht University, defended on 14 May 2001

Study Case 2


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This thesis is about gaps; about canopy gaps in the tropical rain

forest of Guyana which are created by selective harvesting of trees,and about gaps in our knowledge on how these canopy gaps affect

microclimatic and edaphic conditions.

Canopy gaps are a natural feature of the forest and important for

the regeneration of plant species (Bongers and Popma 1988,

Brokaw and Schneider 1989, Whitmore 1989).

As such, trees and gaps define the forest. However, large parts of

the forests in Guyana are logged selectively and as a result,

logging gaps are created. The commercial tree species that are

felled often have heavy seeds, which have a small dispersal radiusso that a clumped distribution of these species is common (ter

Steege 1990). Exploitation of these species ultimately results in

areas of variable sizes being opened up.


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The size of the gap is of particular importance, since research has

shown that trees partition gaps of different sizes (Brown and

Whitmore 1992, Denslow 1980), caused by differences in

microclimatic conditions, soil water availability and nutrient

limitations.

Extensive knowledge of these abiotic variables is needed to assess

the effects of gaps on the regeneration of the forest in general and

for tropical rain forest management of commercial tree species in

specific. This information is needed to devise a forest management

system that is economically beneficial and ecologically sustainable.


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Microclimate in gaps: size matters

Microclimatic conditions were strongly affected by gap size and

shape. The effect of the gap on the microclimate was noticeablebeyond the perpendicular projection of the canopy opening, up to

10m from the gap edge in the largest 3200m2 gap.

Gaps with irregular shaped edges experienced microclimatic

conditions that were similar to smaller gaps, which implies that gapsize alone was not always a good indicator of the potential impact

of a gap on the microclimate.

Microclimate in gaps was regulated by the amount of solar

radiation, which increases soil and air temperature and decreases

air humidity.

The amount of radiation increased with increasing gap size, but air

temperature did not increase above a gap size of approximately

600m2.


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Due to the regeneration of the vegetation in the gaps, airtemperature decreased after two to three years. Soil temperature

was more influenced by soil moisture content and especially by soil

cover than by gap size.

In conclusion, the increasing radiation, temperature and decreasing

humidity with increasing gap size increased the vapour pressure

deficit and thus the amount of direct soil evaporation, which

reduces the amount of soil moisture in the topsoil.

A decreasing amount of soil moisture with increasing gap size can

seriously limit seedling establishment and growth in large gaps.


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A Licence to Fell?

A study on the forest dynamics of the undisturbed forest in the PGEresearch site showed that 95% of the natural tree fall gaps were

smaller than 300m2 and 55% of the gaps were between 25 and

100m2.

These are important figures, since they indicate that the naturalregeneration of the forest occurs within these gap sizes. If it is the

objective of a forest management system to preserve the current

species composition and biodiversity, any logging operation should

not disrupt these figures too much.

Preferably, logging gaps should not be larger than 300m2. Byway of illustration, the mean gap size area that is opened up by

conventional selective logging of one single tree is 181m2 and by

two trees 355m2 (van der Hout 1999).


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Microclimatic conditions in gaps are regulated by the amount of

solar radiation, which is directly related to gap size.

The study of Rose (2000) showed that with increasing gap size,

pioneer species are likely to thrive better than shade-tolerant

species. These latter species are usually commercially interesting

trees.

Modelling the amount of radiation in gaps showed that elongated

gaps, gaps with irregular edges and forest fragments in gaps

notably decrease the amount of radiation in gaps.

A forest management that aims at providing optimal growthconditions for commercial tree species should be aware that

irregular gap edges and forest fragments in logged sites can

promote the growth performance of commercial tree species.


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Nutrient availability can act as a discriminating factor between species

performance in relation to gap size.

In gaps smaller than 200m2, no nutrients were lost due to leaching

and little leaching occurred in gaps of 200 to 400m2.

In gaps larger than 400m2, leaching, acidification and the

mobilisation aluminium strongly increased with gap size.

Considering these aspects of hydrochemistry, logging gaps

should not exceed 400m2.

In conclusion, the research has pointed out that in logging gaps, the

disturbance of the nutrient cycle in gaps larger than 400m2 generatesedaphic conditions that are potentially limiting for all plant species.

Gaps created by selective logging should preferably be smaller that

400m2 size.


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Forest Microclimates

Species differ in the microclimate in which they successfully

regenerate. It is important therefore to gain an understanding of the

microclimates within the rainforest. They are mainly determined

by size of canopy gap.

The microclimate above the forest canopy, which is similar to that in

a large clearing, is substantially different from that near the floor

below mature phase forest.

Close to the ground within to the forest, CO2 content of the air

remains high all the time but up in the canopy it drop in the day dueto uptake by photosynthesis.


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The light climate within the forest is complex. There are 4

components:

1) Skylight coming through canopy holes

2) Direct sunlightseen as sunflecks on the forest floor

3) Light transmitted through leaves

4) Light reflected from leaves, trunks and other surfaces

Light transmitted through or reflected from leaves is greenish

because the orange to red wavelength have been absorbed and

utilized for photosynthesis.

The waveband 400 to 700 nm (approx. the visible spectrum) is

utilized for photosynthesis and is known as photosynthetically Active

Radiation (PAR).


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The forest floor only receives up to 0.2% of PAR incident on the

forest canopy, and 50-80% of this is contained in sunflecks.

Plants living below closed forest probably rely on the sunfleck

component of the light climate for photosynthesis, the other

components are too small to be utilizable.

Within a gap, the microclimate is most extreme in the centre andchanges outwards to the physical gap edge and beyond. The larger

the gap the more extreme the microclimate of its centre.


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Pioneer Tree Species

Pioneer species germinate and establish in a gap after its creation.

They grow fast in height and laggards are suppressed so the canopy

grows up with a strong tendency to be one-layeded.

Below the canopy seedlings of climax species establish and, as the

pioneer canopy breaks up after the death of individual trees, the climaxspecies are released and grow up as a second growth cycle.

Succession has occurred as a group of climax species replaces the group

of pioneer species.

Pioneer species are also called light-demanders or (shade-) intolerants in

reference to their seedling requirements for solar radiation.

Sometimes they are called secondary species because they form

secondary or regrowth forest on cleared surfaces


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Climax Species

Climax species usually germinate and establish below a canopy,

therefore they are perpetuate in situ.

They are called primary species or, with reference to their

seedlings, (shade-) tolerants or shade-bearers.

This is the group which climax (primary) forest is composed, and

climax plant communities are defined as those that are self-

perpetuating, in a state of dynamic equilibrium.


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The main characters of pioneer and climax tree species in tropical rain forests

Character Pioneer Climax

1) Common alternative name Light-demander. (shade-) intolerant,secondary

Shade-bearer, (shade-) tolerant,primary

2) Germination Only in canopy gaps open to the sky

which receive some full sunlight

Usually below canopy

3) Seedlings Cannot survive below canopy in

shade, never found there

Can survive below canopy,

forming a seedling bank

4) Seeds Usually small, produced copiouslyand more or less continuously, and

from early in life

Often large, not copious, oftenproduced annually or less

frequently and only on trees that

have (almost) reached full height

Soil seed bank Many species Few species

Dispersal By wind or animals, often for a

considerable distance

By diverse means, including

gravity, sometimes by only a

short distanceDormancy Capable of dormancy (orthodox),

commonly abundant in forest soil as

a seed bank

Often with no capacity for

dormancy (recalcitrant), seldom

found in soil seed bank

5) Growth rate Carbon fixation rate, unit leaf rate,

and relative growth rates high

These rates low


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Character Pioneer Climax

6) Compensation point High Low

7) Height growth Fast Often slow

8) Branching Sparse, few orders Often copious, often several

orders

9) Growth periodicity Indeterminate (sylleptic), no

resting buds

Determinate (proleptic), with

resting buds

10) Leaf life Short, one generation present, viz.high turn-over rate

Long, sometimes severalgenerations, present so slow

turn-over rate

11) Herbivory Leaves susceptible, soft, little

chemical defense

Leaves sometimes less

susceptible due to mechanical

toughness or toxic chemicals

12) Wood Usually pale, low density, not

siliceous

Variable, pale to very dark, low to

high density, sometimes siliceous

13) Ecology range Wide Sometimes narrow

14) Stand table Negative Positive

15) Longevity Often short Sometimes very long


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SuccessionSuccession

The shift from a secondary forest of pioneers to a primary forest of climaxspecies is called succession

In some big gap pioneer and climax species grow up together, the former

from seed the latter either from seedlings which survived gap formation or

from stem or root sucker shoots.

In this case, where the forest floor has not been completely disrupted,

succession is by simultaneous colonization with the pioneers growing

fastest and initially dominant.

Both modes of succession can be found in the same forest, dependent on the

severity of disturbance.


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Climax species arrive a canopy and establish seedlings under the canopy of a

secondary forest. As the mature phase of pioneers ages, individual trees orsmall groups die and create small gaps.

In these, the climax seedlings are released and grow up as a second growth

cycle below whose canopy climax species establish again.

As that mature phase canopy breaks up these seedlings are released asanother growth cycle.

Climax species as a group thus perpetuate themselves in situ, there is no

directional change in species composition. This is called cyclic regeneration

or replacement.

In a small gap, pre-existing climax seedlings are released. In a large gap,

pioneers which appear after gap creation, form the next forest growth cycle.


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As with pioneers, different climax species may be more successful on someparts of the forest floor.

Dipterocarps are confined to the lowlands and do not penetrate lower

montane rainforest.

The upper limit was shown to be set by the inability of the radicle of agerminating seed to penetrate peat, which develops on the surface above

1050 m elevation.

Seedling establishment is most successful on flat microsites; seedling

stocking diminishes with increasing slope, rapidly at microsites steeper than

45 and falling to nil at 65 slope.

This explains the decrease in numbers of dipterocarps with elevation where

the land becomes more rugged.

Microsite for EstablishmentMicrosite for Establishment


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Many seeds fall near the parent tree and dense carpet of seedlings form.

In several forests, mortality has been shown to be density dependent and,therefore, is greatest near the parent, due to pathogens and herbivores.

The fewer seeds which disperse to a greatest distance are most likely to

grow into seedlings that survive.

This so-called escape hypothesis has been invoked as a mechanism

which prevents rain forest trees forming single-species stands, although

there are exceptions.

For the dipterocarps Shorea leprosula and S. macroptera it was found that

mortality depended more on microsite, and had no relationship to density

or to distance from the parent.

Dipterocarps bear fruit heavily only once every several years. Seedling

populations are then augmented and many attain a density of over one

million per hectare.

Seedling SurvivalSeedling Survival


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Di HHT - Musim pembungaan dan buah berlaku pada setiap waktu di

sepanjang tahun

Tetapi spp. pokok secara individu yang berbunga sepanjang tahun adalah

sangat sedikit

Majoriti pokok - berbunga sekali @ lebih sepanjang tahun dengan renj

yang berbeza

Spp. yang sama biasanya adalah berbunga hampir serentak dalam j/masa

yang panjang merangkumi satu kawasan yang luas

HHT sebagai satu komuniti mempunyai waktu berbunga dan berbuah yang

maksimum dan minimum

Waktu max & min - tidak boleh ditentukan dengan tepat dan berubah-ubah

setiap tahun bergantung kepada faktor-faktor abiotik seperti iklim

Cont: hujan tahunan - jika dapat disukat dengan tepat dan konsisten pada

setiap tahun - waktu 'peak' berbunga dapat dijangkakan

FinologiFinologi


29/43

McClure (1966) dan Medway (1972)

Mixed dipterocarp forest - Ulu Gombak, Selangor

Mencatatkan pembungaan & pembuahan drp 61 pokok (45 spp.) - tahun

1960-69

Kesemua pokok adalah berstrata kinopi

Pemerhatian:Pembungaan adalah max pada bulan Feb-Jun (5 bulan) -

bermula pada awal musim kemarau sehingga mula musim hujan

Bulan Julai - musim berbunga mula menurun

Bulan Dis-Jan - pembungaan di tahap minimum (musimtengkujuh - the wettest of the year)

Musim bunga dan buah adalah bergantung kepada musim hujan

di mana ianya tidak seragam dari tahun ke tahun (1960-69)


30/43

Frankie et al. (1974)

La Selva, Costa Rica

Pemerhatian terhadap pembungaan dan pembuahan selama 2 tahun

Iklim adalah > bermusim berbanding dengan Ulu Gombak. Hujan tahunan

adalah tinggi

Gambarajah A - Pokok-pokok 'overstorey'

- Terdapat 2 'peak of flowering' - but not clearly separated

- Pembungaan bermula dari musim hujan yg pertama (Mei-Jun)

- Minimum of flowering - bulan Nov - 2nd raining season

Gambarajah B - Pokok-pokok 'understorey'- Kurang jelas musim berbunga berbanding dengan pokok besar

- Menunjukkan 3 'peak of flowering' - 2 drpnya terkeluar drp fasa

berbunga pokok besar


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Frankie et al. (1974)

Deciduous forest (tropical dry forest) - Comelco Ranch, western CostaRica

Hujan tahunan - 1533 mm

Musim kering yang panjang (5 bulan) - purata hujan tahunan pada bulan-

bulan tersebut - < drp 100 mm

Pemerhatian:

- Semua pokok adalah 'strongly seasonal in behaviour'

- 'Peak periods of flowering' bermula semasa musim kering yang

panjang - Dis-April

- Menurun apabila bermula musim hujan - Mei-Jun- Musim buah yang max adalah pada penghujung musim kering

tersebut

- Hanya sedikit sahaja spp. pokok yang berbunga pada 3 bulan

terakhir setiap tahun


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Di Afrika - maklumat mengenai musim berbunga adalah amat sedikit

J. S. Gartlan's data (unpublished) (1975-78):

- Dauala Edea Reserve, Cameroon

- Hujan tahunan - 3000-4000 mm- 3 musim kering

- Kajian menunjukkan peratusan pokok-pokok secara individu

berbunga sangat tinggi pada lewat musim kering dan di awal

musim hujan (Feb-Mei)

- Pembungaan adalah minimum pada bulan Ogos - bulan yang

terlembap

Di HHT - musim berbunga dan berbuah, seperti juga penghasilan daun

adalah juga dipengaruhi secara langsung atau tidak oleh faktor keadaan

tanah

Cont: Hutan Paya di Amazonia dan Zaire

- Air pasang berlaku dalam satu jangka masa yang panjang

- 'Mass flowering' berlaku apabila tiba musim air surut


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Kebanyakkan pokok-pokok di HHT adalah berbunga pada masa-masatertentu sahaja

Corner (1988)

- Terdapat spp. pokok di HHT di Malaysia adalah sentiasa

berbunga - 'ever-flowering

- Iaitu ianya mula berbunga pada umur yang muda dan

berterusan sehingga pokok mati

- Kebanyakkannya adalah drp spp. pokok perintis - contohnya:

Adinandra dumosa (Tetiup) - mula berbunga pada umur 2/3

tahun dan berterusan sehingga pokok mati

- Dillenia suffruticosa (Simpoh ayer) - mula berbunga pada umur

18 bulan dan berterusan sehingga 40-50 tahun

Pembungaan Bagi Spesies individuPembungaan Bagi Spesies individu


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'Ever-flowering' bermaksud pokok-pokok secara individu boleh dijumpai

berbunga pada setiap masa di sepanjang tahun tetapi tiada individu pokok

yang dapat berbunga secara berterusan tanpa waktu 'rehat'

Contohnya:

- Dillenia triquetra (Simpoh spp.) di Sri Lanka - ianya berbunga

sepanjang tahun, tetapi pada tahun berikutnya terdapat 1 atau 2

tempoh rehat

- Rhizophora mangle (bakau spp.) di Hutan Bakau Florida -

bunga sentiasa kelihatan sepanjang tahun tetapi tiada pokok

individu yang berbunga secara berterusan

Bagi hutan primer - pokok pokok 'ever-flowering' jarang dijumpai - hanya

berlaku kepada pokok-pokok perintis

Kebanyakkan pokok-pokok di HHT mempunyai musim-musim berbunga

yang tertentu dan pelbagai dari segi frekuensi, j/masa dan keseragaman

waktu berbunga


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Rekod pembungaan pokok di hutan asli dan pokok yang di tanam

(arboretum) menunjukkan perlakuan yang berbeza

- Ashton (1982) mencatatkan 2 spp. pokok dipterocarp di

Arboretum (FRIM, Kepong) adalah berbunga setiap tahun- Tetapi di habitat sebenar ianya berbunga selang beberapa tahun

Corner (1988):

- Pokok-pokok di pinggir hutan di Malaysia biasanya berbunga

setahun sekali, contohnya: Koompassia excelsa (Tualang), Parkia

speciosa (Petai)- Albizia falcataria - 2 tahun sekali

- Syzygium grandis (Kelat) dan Rhodamnia cinerea (Mempoyan) -

beberapa tahun sekali

Holttum (1931; 1935; 1940 & 1953) di Singapura

- Kebanyakkan pokok berbunga dalam j/masa yang seragam - 12

bulan sekali

- Delonixregia dan Lagerstroemia (Bungor) - 7-10 bulan secara

seragam

- Homalium grandiflorum (Telor buaya) - dicatatkan berbunga 12

dan 26 tahun sekali - sangat tidak konsisten


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Pembungaan yang berlaku serentak terhadap sebahagian besar individu

daripada spp. yang sama pada satu-satu masa

Biasanya fenomena ini akan merangkumi satu kawasan hutan yang luas -

> drp 100 km2

Contohnya:

- Dipterocarpaceae - very well known

- Buluh

- Orkid dan pepanjat - kebanyakkan di Malaysia

- Calycolobus heudelotii- di Afrika

Kuantiti bunga yang dihasikan adalah tidak terkira dan diikuti dengan

jumlah biji benih dan anak benih pokok yang sangat banyak

Mass FloweringMass Flowering


37/43

Pembungaan yang tinggi spp. Dipterocarp di H. S. Sepilok, Sabah (1955)

menghuraikan:

"lantai hutan dipenuhi oleh bunga-bunga yang kelihatan seperti

hamparan permaidani"

Gerard (1960):

- Mass flowering of Gilbertiodendron dewevrei, di Zaire

- 11,042,325 bunga dan 10,721 biji benih terdapat dalam satu ha

Biasanya setiap pembungaan secara menyeluruh ini akan mengambil

masa beberapa minggu


38/43

Kebanyakkan spp. drp pelbagai genera ini adalah berbunga dengan

banyak dalam sesuatu masa dan merangkumi satu kawasan yang luas

Tujuannya:

- Menghasilkan bekalan anak benih yang mencukupi dalam

j/masa yang singkat- Sebagai strategi untuk mengelakkan drp pemangsa biji benih

Malesian Dipterocarpaceae:

- Berbunga sekali dalam beberapa tahun, tidak seperti hutan di

Southest Asia yang berbunga setiap tahun

- Secara puratanya 9-11 tahun sekali - 'heavy' flowering- Merangkumi kawasan yang luas

Flowering of DipterocarpsFlowering of Dipterocarps


39/43

Contohnya di Borneo (1955):

- Seluruh Sabah dan Sarawak dipenuhi oleh bunga-bunga drp

famili dipterocarp

- 'Light' flowerings occur between heavy flowerings- > drp 100 spp. dipterocarp yang berlainan berbunga serentak

- tetapi tidak semua spp. individu yang matang berbunga

- juga dicatatkan, terdapat spp. daripada famili lain juga berbunga

pada ketika itu - Koompassia excelsa

Di S. Malaysia, kebanyakkan dipterocarp berbunga di antara bulan Mac-Mei - di hujung musim kemarau pada sesuatu tahun

- J/masa berbunga adalah berbeza di antara spp.

- Biasanya 2-3 minggu

Finologi dipterocarp adalah berbeza mengikut habitat - Shorea albida di

Sarawak tidak berbunga pada masa yang paling kering dalam sesuatutahun

Di Sabah pada tahun 1955 - dipterocarp di kawasan berbukit berbunga

lewat 2 minggu berbanding dengan kawasan pamah


40/43

Buah dipterocarp mengambil masa kira-kira 3 bulan untuk masak. Chan

(1980) mencatatkan buah drp spp. yang lewat berbunga mengambil masa

lebih cepat untuk berkembang berbanding dengan spp. yang berbunga

cepat- Jadi, fenomena ini menjadikan buah daripada spp-spp. tersebut

akan masak serentak

Kehilangan/kerosakan buah dan bunga yang disebabkan oleh pemangsa

dan hujan yang lebat adalah sangat serius

- Oleh itu, 'heavy flowering' adalah penting untuk menghasilkananak benih yang mencukupi untuk survival

- Hanya sedikit sahaja anak benih yang sihat dihasilkan pada

ketika lain

Kajian secara praktikal terhadap fisiologi pembungaan dipterocarp adalahsangat sedikit

Namun, telah terbukti bahawa faktor-faktor iklim memainkan peranan yang

penting - tetapi saling hubungan di antara keduanya adalah terlalu

kompleks dan sukar dihuraikan


41/43

Contohnya, Poore (1968) menyatakan pembungaan dipterocarp adalah

bergantung kepada kekurangan air (water stress) dan diikuti dengan

musim kemarau/kering

Tetapi di Borneo (Wood, 1955) dan di S. Malaysia (Burgess, 1975)

menyatakan 'heavy flowering' yang terjadi adalah tidak konsisten dengan

kadar hujan yang rendah

Terdapat juga bukti menunjukkan terdapat hubungan di antara

pembungaan dipterocarp dengan ketinggian kawasan

Wycherley (1973) menerangkan pembungaan spp. dipterocarp di S.

Malaysia dan Sarawak tidak begitu jelas dipengaruhi oleh kadar hujan

yang rendah tetapi menunjukkan ianya mempunyai hubungan korelasi

yang signifikan dengan renj dan min suhu tahunan

Ashton (1982) menyatakan spp. dipterocarp tidak akan berbunga sehingga

ianya mencapai ketinggian yang secukupnya ataupun sekurang-kurangnya

sebahagian drp kinopinya terdedah kepada cahaya matahari


42/43

Kadar pembungaan pokok yang maksimum dan minimum selalunya akan

diikuti oleh penghasilan buah yang juga maksimum dan minimum

Di S. Malaysia, Medway (1972) menyatakan pada tahun 1963-69, purata

peratusan pokok berbunga sangat tinggi pada bulan Jun-Julai dan diikuti

oleh penghasilan buah yang maksimum kira-kira 8 minggu kamudian

Di La Selva, Costa Rica - 'Peak of flowering' bagi pokok 'overstorey' adalah

pada bulan Mei dan diikuti dengan 'peak of fruiting' pada bulan September

- beberapa bulan kamudian buah akan masak seterusnya

mengugurkan biji benih

- 'Peak of fruiting' bagi pokok 'understorey' adalah lambat sedikit

berbanding dengan pokok 'overstorey' iaitu pada bulan Oktober

(Frankie et al., 1974)

FruitingFruiting


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Penghasilan bunga yang banyak tidak semestinya akan menghasilkan

buah yang banyak

Terdapat beberapa faktor di mana bunga dan buah yang belum cukupmatang akan rosak/musnah oleh hujan lebat, fungi dan pemangsa

Terdapat beberapa variasi j/masa yang diambil oleh pokok daripada

perkembangan buah sehingga ianya masak

- Kebanyakkan spp. mengambil masa 2-3 bulan untuk masak

- Durian (3 bulan); Mangga (2-5 bulan); Koko (4-5 bulan)

Bagi spp. pokok yang mempunyai buah yang kecil dan disebarkan oleh

angin, biasanya perkembangan buah adalah lebih cepat

Proses perkembangan buah drp pembungaa tidak semestinya berterusan

Hymenaea courbaril- buah membesar sehingga ke saiz matang hanya

dalam j/masa 1/2 bulan sahaja drp waktu berbunga, tetapi masih lagi kekal

di atas pokok untuk beberapa bulan lagi dan seterusnya buah yang masak

akan jatuh pada musim kering

forest dynamics note

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