Tropical Rainforest Gaps And Tree Species Diversity
Annual Review of Ecology and Systematics (Impact Factor: 10.97). 11/1987; 18(1):431-451. DOI: 10.1146/annurev.ecolsys.18.1.431
Summarises recent information on the nature of gap-understorey environments, paying particular attention to the role of light amount and duration, soil nutrient availability and soil moisture and gap dynamics (focusing on gap-size frequency distributions and forest turnover rates). Patterns of growth and mortality are noted. Evidence is considered regarding habitat specialisation by tropical trees, reviewing data on the distribution of adult and juvenile trees, and on the relative performances of similar species along gap-understorey gradients. Discussion centres on life history attributes in a gap-understorey mosaic.-P.J.Jarvis
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- "We conducted a canopy reduction treatment 4 years after planting in order to study the growth response to increased light availability, and examine how the responses varied with tree species' traits. The canopy reduction treatment was conducted to imitate the gap dynamics of a tropical rainforest (Denslow, 1987), and this sort of treatment is applicable for practical enrichment planting projects. We used traits to predict the tree species' responses in height growth to treatment (Table 1). "
ABSTRACT: Rainforest restoration is an important application in today's multipurpose management of secondary forest. However, our knowledge of tree species' traits and responses to treatment is insufficient for foresters to make good decisions for sustainable management. The aim of our study was to see whether it is possible to predict tree species' responses to increased light based on species' traits, and to relate these responses to a possible pioneer-climax continuum of life history traits, also among species with presumed climax properties. We examined 33 taxa (including 19 from the dipterocarp family) replicated 20 times and randomly planted in lines over a 3. ha area in the interior of Sabah, Borneo. Four years after establishment we performed a canopy reduction treatment to increase the light conditions up to levels present in tree gaps in the forest. We created a PLS (Partial Least Square Regressions) model with the two predicted variables HGR (height growth response) and Q3 HGR (the 75 percentile of a species' HGR, interpreted as the potential HGR). The model captured 47% of the variation for the predicted variables. We found significant tree species' responses in height growth to the increased light. High specific leaf area, strong early height growth, high foliar N content, high leaved stem length and large crown were linked to fast growth, while high wood density and high foliar K content were associated with slow growth. We also found a trade-off between growth response and survival among the species. We conclude that climax tree species have specific life history adaptations along a pioneer-climax continuum, which can be predicted from species' traits. The importance of easily observed or extracted traits such as initial growth rate, specific leaf area and wood density for predicting growth suggests the possibility of fast screening of species with unknown characteristics, which could be of great value in practical forest management.
- "However , because of the lack of similarly detailed and large scale data from other fragmented systems , whether this is occurring at a rate that is unique to Hawaiian montane forests in unknown . Because larger gaps require even more time to fill , there may be increased opportunity for woody plant species with multiple growing strategies to enter the site ( Denslow 1987 , Levey 1988 , Laurance et al . 1998a , Brokaw and Busing 2000 ) . "
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- "Most woody plant species in tropical forests exhibit contagious ( " clumped " ) distributions, such that individuals are found in closer proximity to others of the same species than expected by chance [Condit et al., 2000; Hubbell, 1979]. Thus, the local densities of particular species often vary considerably among areas within an animal's home range [Potts and Lwanga, 2014], especially in highly heterogeneous ecosystems in which adjacent microsites vary in factors that influence plant productivity [e.g., soil nutrient concentrations, irradiance, altitude , and temperature; Clark et al., 1998; Davies et al., 1998; Denslow, 1987; Hubbell et al., 1999]. Because frugivorous primates frequently feed preferentially on a small number of spatiotemporally rare plant items, high-quality foods are typically widely dispersed. "
ABSTRACT: Although numerous ecological and social factors influence range use in vertebrates, the general assumption is that ranging patterns typically accord with principles of optimal foraging theory. However, given temporal variability in resource abundance, animals can more easily meet nutritional needs at some times than at others. For species in which sociality is particularly important for fitness, such as chimpanzees (Pan troglodytes) and other group-living primates, the influences of social factors can be particularly strong, and likely interact closely with ecological factors. We investigated home range use by a community of chimpanzees at Ngogo, Kibale National Park, Uganda, to determine whether range use corresponded to energy-based optimality principles. Chimpanzees were particularly attracted to areas of the home range where individuals of Ficus mucuso (a large but low-density resource) were found, but only if those areas also offered other preferred or important resource classes. The aggregation of large foraging parties at F. mucuso crowns (frequently seen year-round) facilitates a number of socially beneficial activities for both males and females. Because chimpanzees apparently seek out F. mucuso in areas where other high-quality feeding opportunities exist, these social benefits likely do not come at the expense of fitness benefits accrued from feeding on high-quality resources.