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J. Biosci., Vol 18, Number 4, December 1993, pp 501–514. © Printed in India.
The community ecology of Asian rain forests, in relation to
catastrophic events
Ρ S ASHTON
Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue,
Cambridge, Massachusetts 02138, USA
MS received 14 August 1992
Abstract. Although natural catastrophic disturbance of tropical forests in Asia can be
caused by volcanism and earthquakes climate-induced catastrophes are most widespread.
These are prevalent and most diverse at high tropical latitudes because of the single annual
dry and wet monsoon. Comparative studies indicate that periodicity of catastrophes may
influence forest physiognomy, structure and species richness but long-term research in
sample plots suggests that a variety of other factors are locally influential. The importance
of accounting for natural catastrophes in silvicultural protocols is stressed, and research
priorities identified.
Keywords. Asia; tropical forest; catastrophes; biogeography; community structure.
1.
Introduction
One reason for the extraordinary biological diversity which so distinguishes the
evergreen forests of the lowland humid tropics from other terrestrial ecosystems
could be their great age. Ecological (Bews 1927) and comparative morphological
(Corner 1949) evidence has been used to argue that the flowering plants originated
in the humid tropics, where many archaic forms still persist in the lowland rain
forest. It has long been known that African rain forests, generally acknowledged to
be less species-rich than those of other continents (Richards 1952; Meggers et al
1973), experienced massive changes in distribution owing to climatic changes during
the Quaternary (e.g. papers in Meggers et al 1973). Plate tectonic (Smith and Briden
1977; Smith et al 1973) and paleontological (Muller 1972), evidence supports the
views of Posthumus and van Steenis (quoted in Richards 1952, p 14) that Far Eastern
rain forests may have persisted in situ at least since the Tertiary. At the same time, the
favourableness of wet equatorial climates for plant growth, their equability and, in
some regions such as the Far East, their comparative lack of seasonality has been
held to favour survival of biological diversity (Richards 1952), perhaps under low
selection pressures (Corner 1954; Fedorov 1966).
In recent decades these perceptions, all pointing to the relatively great stability of
the southeast Asian tropics, have taken a battering. In both equatorial South
America and the Far East (Flenley 1979; Morley and Flenley 1987; Whitmore and
Prance 1987) major changes in rainfall seasonality are now known to have
periodically occurred in late Miocene and Pleistocene times. In the latter this has
been thanks both to continued mountain building and, during Pleistocene times, to
the advance and retreat of epicontinental seas over the extensive Sunda and Sahel
continental shelves. This realization has led to the concept of refugia: areas where
both regional and point endemism and species diversity appear now to be
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concentrated, and which may on that evidence have experienced less extinction, and
therefore by inference less or no climatic change during the Quaternary (Brown
1987 for South America but see also Bush et αl 1992; Ashton 1972; Morley and
Flenley 1987 for the Far East).
At the same time, evidence for occasional catastrophic modification of tropical
forest has been coming in from many regions and is the subject to be reviewed in
this paper. Both the kinds of catastrophes and their impacts are various and
characteristic. Table 1 provides a summary of what has, so far, been mainly casual
observation.
Table 1. Agents of catastrophic disturbance in Asian evergreen forests.
1.1 Agents of disturbance
While forests that experience frequent strong winds appear to be adapted to them,
notably by their short stature and smooth canopy structure (Vaughan and Wiehe
1937; Beard 1945, 1946), the catastrophic influence' of occasional, unpredictable
storm damage at the margins of the typhoon belt has long been recognized. WyattSmith (1954) described a storm-influenced forest in Kelantan, and Webb (1958) in
Queensland, Australia. Such effects have been documented in detail over time in the
classical studies of Whitmore (1974, 1989a).
Catastrophic effects were apparent during the extraordinary dry season of 1982—
83, when many regions from east Asia through to Australia experienced killing
droughts. The El Nino southern oscillation (ENSO) event was the strongest recently
recorded. The eastern lowlands of Borneo were particularly severely affected
(Leighton and Wirawan 1986), and the damage was greatly increased by maninduced fire. Without fire, high mortality was recorded among early regeneration
but also, more significantly, up to 30% of emergent trees died on well-drained
ridges. This mortality was highly species-specific (personal observations, April 1984).
Landslips occasioned by earthquakes and rain storms can occur on a widespread
Community ecology of Asian rain forests
503
scale in steep juvenile topography, especially in equable and wet equatorial regions.
Some of their effects have been documented in central America (Garwood et al
1979) and New Guinea (Johns 1986). Whereas wind squalls lead to tree uprooting
with exposure of the mineral soil beneath, and a patchy cover of fallen litter
beneath the canopy gap created, landslips strip most or all of the soil leaving a
mineral surface initially devoid even of dormant seeds. Landslips can thus sharply
differentiate the soil conditions of ridges and slopes and the floristic composition
and dynamics of their forests (see Whitmore 1984, chapter 17.3 for further
discussion). In addition, major volcanic eruptions can create new surfaces free of
seeds on a much larger scale (Flenley and Richards 1982).
1.2 Models of disturbance and biodiversity
So widespread has the evidence of catastrophic events in tropical rain forests
become that the existence of any areas free of them is now being called into
question. The longstanding debate between those who have claimed that stochastic
events create an unpredictable, non-equilibrium floristic structure in species-rich
tropical forests (e.g. Fedorov 1966; Hubbell and Foster 1986), and those who
envision a dominant role for probabilistic events, increasing refinement of niches,
and hence an equilibrium mode in which species diversity is maintained (Ashton
1969; Janzen 1970; Terborgh 1992) is far from resolved. Rather, it is becoming
sharpened. At the same time, though, the evidence for species-specific natural
selection and density-dependent selection even among trees, at least among the
more abundant species, continues to increase.
Hubbell and Foster (1990, 1993) showed that juveniles of a majority of species,
rare as well as abundant, had higher mortality and lower growth close to mature
conspecific crowns than to crowns of other species. Niche specificity has been
documented among the abundant and often extensive series of closely related yet
ecologically sympatric species which characterize Far Eastern lowland forests (Ashton
et al 1988; Rogstad 1986; P M S Ashton 1990; S.H Rogstad, unpublished results).
Coexistence of such finely differentiated ecotypes implies that physical conditions
have remained equable over evolutionary time, whether their existence is the result
of species specific natural selection in situ, or gradual accretion of randomly
differing taxa through immigration. The prevalence not only of dioecy (Ashton
1969) but also pf outbreeding (Bawa 1974) and high genetic variability (Hamrick
and Loveless 1989; Hamrick and Murawski 1991) among rain forest understorey
trees implies that sex is worth the considerable cost to fecundity imposed by their
spatial isolation in and beneath the canopy. It remains difficult to explain the
benefits of maintaining high genetic variability in an environment which remains
equable over evolutionary timescales, except by assuming high species-specific
competition. Such competition, most frequently between tree species and animals or
microorganisms, will then change continuously over time as immigration and
differentiation proceeds.
Connell (1978), drawing analogy between coral reefs and tropical forests, proposed
that tree species diversity in rain forests will be greatest where disturbances are
moderate in intensity and frequency. Low disturbance will lead to eventual
dominance of the mature phase (in the sense of Watt 1947) canopy by a few species,
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P S Ashton
while consequent isolation, predominant small size (e.g. Sanford et al 1986) and the
ephemeral nature of canopy gaps will sustain high extinction rates and limited
immigration opportunities, preventing the build-up of a rich pioneer flora. High
disturbance will militate against accumulation of the 'climax' species (in the sense of
Whitmore 1989b) which represent the majority of large trees in most rain forests;
but moderate disturbance will favour species dynamics that prevent monospecific
dominance in the mature phase, and also reduce the chance of extinction and
increase the immigration in gaps. This prediction is relevant at scales smaller than
the whole community because intermediate levels of disturbance will favour good
representation of both pioneer and climax species in small samples. At a larger scale
it only applies if disturbance patterns remain relatively constant over evolutionary
time, thus allowing for optimal rates of immigration and speciation for pioneer and
climax species to come into balance with extinction rates (MacArthur and Wilson
1967). The 'intermediate disturbance hypothesis' therefore provides an equilibrium
model of forest community structure; but its proper application appears limited to
an ecosystem with a more constant disturbance regime at ecosystem scale, like the
coral reef. Although the developmental structure of coral reefs mandates that zones
of differing intensity of disturbance always exist in contiguous balance, regimes of
allochthonous disturbance are rarely likely to remain constant over time in
terrestrial ecosystems.
1.3
Anatomy of tropical forest disturbances
Forest catastrophes primarily affect the canopy of the mature phase, which, opened
up, thereby affects the climate beneath and conditions for regeneration. These two
effects of disturbance vary independently in their nature and intensity (Whitmore
1990, chapter 7.6). The major influence on canopy disturbance in tropical forests is
the width of the gap in relation to forest stature, because the sun is nearly overhead
at noon but gap width will determine the number of hours of direct sunlight that
penetrates beneath. By contrast, variation in light across gaps, north to south,
determines the major gradient in temperate climates on account of the
comparatively low inclination of the sun during the growing season.
Agents of canopy disturbance (table 1) create gaps of differing size. Senescence,
disease, and lightning strikes cause single tree mortality; windthrows of individual
emergents bring down groups of trees, and larger-scale perturbation is caused by
earthquakes, drought and typhoons. Those caused by physical agents are always
more frequent in some habitats than in others: lightning strikes and droughtinduced mortality are common on ridges, as are landslides on scarps, and typhoons
on windward slopes and gullies. Some sheltered cove forests may never experience
any such disturbances.
At the ground, the degree of mortality of established regeneration and the degree
of soil surface scarification, besides the amount of litter, are the principal
determinants of succession. This is because they determine the life history stages
and consequently the ecological characteristics of the plants available for forest
regeneration; and the physical conditions for seedling establishment. Landslips,
volcanic eruptions, droughts, fires and uprooted trees remove established
regeneration of climax species which have established in the shade of the
understorey. All may also influence the character of the soil surface, particularly the
Community ecology of Asian rainforests
505
density of litter and presence of raw humus, both of which may be critical to
seedling establishment; so may floodwater. Removal of surface soil may reduce the
store of dormant seeds.
2. Catastrophic disturbance in tropical Asia and the Far East
Relative effects of different types of catastrophic events in the forests of southeast
Asia and the Far East lead to some productive insights on disturbances and forest
structure. My intention in this section will be to identify questions for research,
rather than to give definitive answers: that can only be done by careful, quantitative
description of large forest samples before events and subsequent monitoring after
them (e.g. Whigham et al 1991; Lugo and. Waide 1993), for which I have no example
in the region other than in small plots.
2.1 Influence of latitude and seasonality
Major regional catastrophic events, which include droughts, typhoons, fire and frosts
in tropical Asia, are the more influential in their effects the more rarely they occur.
It is therefore at their geographical margins, where incidence is least frequent, that
their influence is catastrophic. Where they occur regularly, they act as major
limiting factors to which the structure and dynamics of vegetation equilibrates. The
influence of widespread catastrophic events is greatest at higher latitudes within the
tropics where year-to-year variability in rainfall and minimum temperature, and
temperature range, peaks in continental regions, and where the hurricane zone
occurs along eastern coasts (von Riehl 1954). It is least in the intertropical
convergence zone along the climatic equator, particularly in oceanic and mountain
regions of the Indonesian archipelago, Melanesia and southwest Sri Lanka where
topography including orography assists in the maintenance of equable conditions,
Nevertheless, few regions appear to be completely devoid of catastrophe, It may
therefore be appropriate to ask to what extent current catastrophes, rather than
past climatic events, can explain in particular floristic ecology and the species
richness of both forest communities and biogeographic regions.
In tropical Asia, seasonal drought and winter frost independently limit the
extension of tropical rain forest. The influence of both are determined by the unique
climatic system of the region, which is dominated by the southeast wet monsoon off
the southern oceans. This alternates with the northeast dry, winter monsoon off
Continental Asia, mandating single annual wet and dry seasons of varying length.
The rainfall seasonality limits of evergreen rain forest are marked, in the absence
of other factors, by a gradual increase in deciduousness, at first in the emergent,
then in the main canopy and finally within the whole forest (Richards 1952).
Deciduousness varies continuously with topography and therefore, by implication,
with the duration and intensity of dry-season soil water defecits. Fully deciduous
forests consist exclusively of fire-resistant species and presumably have always
experienced periodic fire in nature. Nowadays, man-induced fire is almost
ubiquitous in the strongly seasonal tropics. Such burning has created a sharp
boundary between evergreen and moist mixed fully deciduous forest (Ashton 1991),
and led to a decline of the intermediate communities into complex mosaics
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P S Ashton
determined by their histories of man-made fire or clearance (Legris 1963 and in
detailed regional studies). Here, then, is one critical interphase, between forests of
very different composition and dynamics. These have different economic value,
silvicultural characteristics, biomass and carbon content; their gas-exchange
characteristics with the atmosphere also are likely to vary (Keller et al 1991).
Formation of such forest mosaics varies according to unpredictable physical factors
that may reflect global climatic change, yet this has never been the subject of
rigorous or long-term research.
Preliminary information on the change of species richness from evergreen through
deciduous forests to fire-dysclimax savanna is becoming available for studies under
the direction of S Sarayudh Bunyavechewin at Huai Kha Khaeng Wildlife Sanctuary,
Thailand. There, in a climate with 1800 mm mean annual rainfall and five dry
months, mixed evergreen forests in moist valleys contain c. 160 tree species; in
adjacent moist deciduous forests include less than one hundred, while in the dry
Dipterocarp savanna forest there are just thirty. Whether these differences are due to
differences in constantly limiting factors or differentials in frequency of catastrophic
fire or extreme soil water deficits is so far unknown.
Frost limits both the altitudinal and latitudinal extents of tropical evergreen
forest (Whitmore 1984). Frost incidence, to which seedlings are more sensitive than
canopy trees, is reduced by high atmospheric humidity immediately above and also
within forest canopies. Currently, catastrophic canopy mortality is occurring in
some isolated montane rain forests in or at the margin of seasonal dry climates in
northern Thailand (e.g. Doi Inthanon), Sri Lanka (the eastern margin of the Horton
Plains) and elsewhere. It is possible that this is being induced by lower atmospheric
humidity, consequent upon deforestation downslope. At the latitudinal margins of
lowland rain forest in South China, pastures created by forest conversion are
dominated by temperate agrostoid grasses and herbs including Viola and Corydalis
(personal observation). Here, too, deforestation may increase the risk of periodic
catastrophic frost mortality, but no research has yet been initiated to monitor
these effects either.
To date, data do not exist which can permit any correlation between frost incidence
in tropical forests and species richness to be ascertained. There is generally a decline
of tree species richness with altitude (see e.g.. Richards 1952), but this begins at least
by 1000 m ascent, well below the frost line. The only exception is where more or
less a seasonal montane climates are surrounded by more seasonal lowlands as in
south Asia. There, maximum species richness occurs immediately above 700 m,
within the more equable climate of the cloud base (see e.g.. Gunatilleke and Ashton
1978); this zone is also associated elsewhere with maximum species richness of
shrubs and epiphytes (Gentry 1982), although no quantitative data yet exist for Asian
forests.
2.2
Global changes and catastrophic events
Global climatic change may effect changes in the local frequency of catastrophes,
and introduce catastrophic climatic disturbances into forest unadapted to them.
Regional changes in the frequency and disturbance of typhoons have occurred (e.g.
Whitmore 1989a) and may be associated with global change.
Community ecology of Asian rain forests
507
Nowhere can the striking difference in forest dynamics in relation to storm
frequency be observed more clearly than down the eastern seaboard of the
Philippine islands. Along the eastern slopes of the northern Sierra Madre of Luzon,
forest composition is similar to that of climax forests on the lee of the hills inland,
but structure is distinguished by short stature, and an even canopy of gnarled
crowns with noticeably diffuse foliage. In 1975 I witnessed a typhoon pass through
a forest east of Real, Quezon. Though there was much loss of leaf, the forest itself
held firm, and few trees or branches were broken. Later that same year I witnessed
the trail of destruction left by the strongest typhoon in forty years in the
magnificent forests at Bislig Bay, eastern Mindanao, which are now fully destroyed
by man. Swathes of climax forest were flattened and, strikingly, plantations of largeleaved pioneers, such as the South American Cecropia, were particularly badly
mutilated. I have witnessed local massive windthrows in the equable wet regions in
the hilly inlands of Brunei and Sarawak, Borneo, where Anderson (1964)
documented occasional large-scale withthrows in the coastal peat swamps. In Asia,
occasional, and therefore particularly catastrophic hurricanes occur also in
peninsular Thailand and Malaysia (Wyatt-Smith 1954; see also Whitmore 1984) and
on the windward slopes of the Arakan range and Chittagong hills bordering the
northern Bay of Bengal.
2.3 History of disturbance
Confirmatory palaeontological evidence for climatic constancy over geological time
requires a continuous palaeontological record, which is particularly difficult to secure
in the lowland humid tropics. The strongest, albeit never confirmatory, evidence
remains biogeographic. Particularly convincing are indications of coincident
patterns of vicariance among species of unrelated taxa on either side of old,
persisting physical boundaries, local and regional concentrations of endemism, and
exceptional local and regional species richness in widespread community types,
particularly those which occur in ecological island habitats. Data for the latter is so
far only available in the Far Eastern tropics. They indicate that such habitats in the
equable lowlands can sustain species-rich tree communities in areas as small as
100 km 2 in some regions (Ashton 1984 and unpublished data). It is impossible to
determine whether richness on this scale has been achieved mainly through low
extinction rates or through continued immigration, although the high richness and
point endemism among short-lived species of distinct floras such as that of karst
limestone implies that persistence in remarkably small ecological islands remains
important.
Two regions outstanding in these respects are the northwest Borneo lowlands,
from Kuala Kapuas in Kalimantan Barat to Beaufort in southwest Sabah (Ashton
1972, 1984, 1993); and the wet southwest quarter of Sri Lanka (Ashton and
Gunatilleke 1987). The former is distinguished on all three criteria, the latter only
on the first two owing to lack of adjacent regions under the same climate with
which to compare it. Northwest Borneo and East Kalimantan do not show striking
differences in tree species richness in samples of mixed dipterocarp forest from the
widespread clay udult ultisol soils. However, samples on heath forest on spodosols
from the northwest contain more than twice as many species than others from the
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east; while local endemism in heath forest and mixed dipterocarp forest on yellow
sand humult ultisols in the former is many times greater than the latter in some
families (Ashton 1984). Both these soils, and their associated floras, are confined to
island patches, mostly in the coastal lowlands. The dramatic differences between the
northwest and eastern floras of Borneo could as well be explained by selective
culling of species during the periodic catastrophic droughts and fire experienced in
East Kalimantan as by climatic change during the Pleistocene. This is supported by
the evidence of charcoal in spodosol profiles from primary forest in East
Kalimantan, which has so far not been seen in the northwest. Here again is an issue
ripe for long-term study.
2.4
Small-scale catastrophe and soil type
Forest communities in southeast Asia may differ in the predominant manner and
frequency in which canopy gaps are formed, and these local and small scale
catastrophic events may affect the overall dynamic and floristic characteristics of
the forest (Ashton 1992; Ashton and Hall 1992). Such events will be most easily
interpreted when other, more widespread catastrophes are rare or absent. Three groups
of 0.6 ha plots were established on contrasting soils in the mixed dipterocarp forests
during 1964-65 under the sponsorship of the Sarawak, northwest Borneo Forest
Department. The results after twenty years of measurement have been published
elsewhere (Ashton 1992; Ashton and Hall 1992) and I will merely summarize them
here. The groups, of 4-5 plots each, were sited on shallow humult ultisols
overlooking the coast, on deep inland humult and udult ultisols, and oxisols over
basalt. Soil mineral concentrations increased in that order, and were considerably
higher in the oxisols than in the rest. Soil water retaining capacity is also thought to
increase in the same sequence (though data are unavailable).
The forests on shallow freely draining soils are shorter in stature than the other
two, with relatively even canopy and few emergents. The other two forests are
similar in stature; but that on deep ultisols has scattered emergents, whereas
emergents in forests on basalts form an almost continuous canopy except where a
gap has been formed. Each forest has a distinct flora, but differs substantially in
species richness which is highest on the intermediate, deep ultisol soils, where it is
concentrated in the main canopy. Species richness is negatively correlated with the
population density of the most abundant species on higher nutrient udult ultisols and
oxisols, but not on humult soils where it is positively correlated with concentration
and spatial variability of certain soil nutrient concentrations. Gaps are small in low
stature forests owing to the short trajectory of falling trees, and on humult soils
where more trees die individually, standing than on udult ultisols and oxisols where
more are uprooted, carrying others with them.
2.5 Summary
I have discussed these forests in some detail because we believe that the pattern of
species richness in them can only partly be explained by the difference in disturbance
patterns. A distinct guild of large pioneers which reach the canopy at maturity,
Community ecology of Asian rain forests
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Ρ S Ashton
Community ecology of Asian rain forests
511
Figure 2. (a) Stereopair of mixed dipterocarp forest over Miocene sandstone, Lambir
forest, Sarawak, NW Borneo, three months after major rainstorm in 1965. Note the
concentration of landslips on steeper slopes, and on softer rocks where crown sizes are
bigger and soils deeper, (b) One such landslip. Lambir forest (foreground) from the lower left of
(1), photographed in 1986. Woody vegetation on these poor soils has generally not reached
4 m (Photo: Ρ Hall) (c) Seasonal evergreen dipterocarp forest at its climatic limits, Doi
Inthanon, NW Thailand, on clay soils on lower moist slopes, January 1990. The
dominance of bamboo in the understorey is due to periodic fire incursion from adjacent
dry deciduous forest upslope. (d) Forest fire, Mai Hon Son, NW Thailand, January 1990.
Forest fires in the humid tropics are almost always ground fires, (e) Swathes of dead
seasonal evergreen dipterocarp forests originally caused by application of chemical
herbicides, Ma Da forest, Dong Nai Province, Vietman, January 1983. In accessible areas
as here, the swathes are expanding because hunters burn them during the dry season to
encourage the young shoots of Imperata cylindrica (L.) Ρ Beauv and other coarse perennial
grasses, which attract wild ungulates, (f) Logged forest in East Kalimantan three years
after the catastrophic droughts and fires of 1982-1983. Here the forest cover has been
killed in the foreground, and early succession has been affected by domination of the
climbing fem Dicranopteris linearis (Burm. f.) Underwood. (Photo: W Smits). (g) Mixed
dipterocarp forest in East Kalimantan, Indonesian Borneo, one year following the severe
drought of 1982-83. Note dead crowns on ridges (Photo: S Yasuma).
which is more species-rich and more abundant on high nutrient oxisol and ultisol
soils than elsewhere, fails to offset the depression of overall tree species richness on
these high nutrient soils. Low species richness in the mature phase of forest on
oxisols is associated with a dense emergent overstorey composed of a small number
of fast-growing light-hardwood climax species, and marked vertical stratification in
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Ρ S Ashton
Table 2. Priorities in future research.
■
Long-term research at representative forest sites throughout the region at which stand
and population dynamics are monitored before and subsequent to various kinds of
catastrophic disturbance.
■
Adoption of methods which allow statistical comparability between sites. These would
include:
Measurement of canopy topography;
Samples large enough to allow demographic analysis of both common and rare
species, and to record their interaction over time;
Measurement of physiological stress in plants during and after catastrophe;
Associated measuring of climate and soil.
which the main canopy is poorly represented. We hypothesize that species richness
on udult soils is greatest where occasional catastrophic drought periodically culls,
and increases the surface roughness, of the canopy, thereby increasing the amount
and spatial heterogeneity of the light beneath it as observed by Terborgh (1985).
These conditions may occur on ridge tops, and also on lower nutrient clay ultisols
which lack structure, are poorly drained and have shallow rooting. Conditions
within the mature phase of these forests are thus optimal for survival and even
regeneration of subcanopy and canopy species, while the diversity of light
conditions favours diversification of the 'regeneration niche' (Grubb 1977). These
differences in the gap regimes of different habitats and their associated forest types
are partially independent of the vicissitudes of local climate. Provided the climate
does not change, their differences may be expected to persist over evolutionary time,
thereby influencing the total pool of species in each forest community type. In this
case, species richness may be enhanced, rather than depressed, by rare or only
moderate culling of the emergent canopy by drought-induced mortality, as Connell
(1978) predicted.
Natural catastrophic intervention occurs in Asian tropical forests on a vast
diversity of temporal and spatial scales, and this diversity is habitat related,
influencing forest types differentially in ways which, if understood, can be predicted.
Understanding the impact of catastrophes is therefore critical to improved forest
management. It can only be achieved through painstaking monitoring of
representative forest samples over prolonged periods, and by recording conditions
before as well as after catastrophic events. I summarize priorities for research in
table 2. Hypotheses of causal relationships must be tested by experimental
manipulation, and results used to design optimal silvicultural protocols. In order to
better manage tree species diversity itself, samples must be large enough to monitor
the demography of the vast majority of species, whose populations are dispersed at
low densities. To this end, it is a particular pleasure that colleagues in several
Japanese institutes, including Kyoto and Osaka City Universities, are collaborating
with us at the Center for Tropical Forest Science of the Smithsonian Institution,
and with scientists in a number of research institutes in tropical Asia who have
taken up the challenge of initiating such research upon a regional basis. With
increasing evidence of global climatic change which may have profound, even
devastating, effects on the center of global biological diversity which is the tropical
evergreen rain forest, this meeting of minds and hands could not have come at a
more auspicious time.
Community ecology of Asian rain forests
513
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