Assessing Evidence for a Pervasive Alteration in Tropical Tree Communities

In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16–52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha−1 y−1, 95% confidence intervals [0.07, 0.39] MgC ha−1 y−1), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55] % y−1) compared with the tree community as a whole (+0.15 % y−1); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 [0.02, 0.37] % y−1), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests

A NOTE ON THE GROWTH HABIT OF FRINGED POLYGALA

Volume: 85Start Page: 457End Page: 46

Liana diversity and species richness of Malaysian rain forests

The contribution to woody plant diversity by lianas was examined in a lowland and hill dipterocarp forest in Peninsular Malaysia. Species richness of lianas is found to be as high as that visually found in the species-rich moist forests of South America. As in Africa and South America, lianas appear to constitute about one-quarter of the woody flora in the evenvet lowland forests of Peninsular Malaysia. Consequently, the total woody plant diversity in Peninsular Malaysia is at the same level as that found in the ever wet forests of South America. The present study also confirmed the existence of intercontinental variation in liana floristics, with Annonaceae being the dominant liana family in Asia. Another distinct feature differentiating Malaysian forests from the rest of the tropics is the dominance of rattans among the Malaysian liana flora. These plants appear to be particularly abundant in the upper hill dipterocarp forests. While their role in the ecology of the forests deserves a more critical examination, the potential for cultivating them in the upper hill dipterocarp forests should also be looked into

Forest Environments in the Mekong River Basin.

Until now, there have been few research works on Cambodian forests because of the long period of civil war, which restricted forest researchers and surveyors in the area. This book presents many new topics of research in forests such as those of Cambodia which were unavailable until now. One of the most attractive features of the volume is that it fills the gaps in data about the world’s forests. The book consists of three parts: forest hydrology, forest management, and forest ecology, designed to provide an understanding of continental river basins. The latest data are presented here, as derived from advanced observation systems for atmospheric flux, ground water level, soil water movement, and stable isotope variation as well as remote sensing, which are used for continuous measurements of forest environments. These research results provide a bounty of fresh scientific information, creating a valuable resource not only for researchers and university students but also for forest administrators. Table of contents Part 1: Forest Hydrology Part II: Forest Management Part III: Forest Ecolog

Nonrandom processes maintain diversity in tropical forests

An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems