Dynamics and species richness of tropical rain forests.

We present a worldwide analysis of humid tropical forest dynamics and tree species richness. New tree mortality, recruitment, and species richness data include the most dynamic and diverse mature tropical forests known. Twenty-five sites show a strong tendency for the most species-rich forests to be dynamic and aseasonal. Mean annual tree mortality and recruitment-turnover-is the most predictive factor of species richness, implying that small-scale disturbance helps regulate tropical forest diversity. Turnover rates are also closely related to the amount of basal area turnover in mature tropical forests. Therefore the contribution of small-scale disturbance to maintaining tropical forest diversity may ultimately be driven by ecosystem productivity.

Increasing turnover through time in tropical forests.

Tree turnover rates were assessed at 40 tropical forest sites. Averaged across inventoried forests, turnover, as measured by tree mortality and recruitment, has increased since the 1950s, with an apparent pantropical acceleration since 1980. Among 22 mature forest sites with two or more inventory periods, forest turnover also increased. The trend in forest dynamics may have profound effects on biological diversity.

Use and Misuse of Forest-harvested Fruits in the Iquitos Area.

Of 193 fruit species observed to be regularly consumed in the region surrounding Iquitos, Peru, 120 species are exclusively wild-harvested and 19 more originate from both wild and cultivated sources. The wild-harvested fruits of 57 species belonging to 24 different plant families are sold in the Iquitos market and are very important in the economy and diets of the area Nearly half of the Iquitos fruit vendors sell wild-harvested fruits (if fruits used as vegetables or starch sources are excluded), and over half of the fruit species sold are wild-harvested Many fruit species consumed at Iquitos differ from those consumed in other parts of Amazonia Although some native fruit species are beginning to be grown as crops, the wild populations of these high-potential species are being rapidly depleted by destructive harvesting techniques as market pressure begins to build In the last few years, the availability of several of the most popular fruit species has decreased markedly. If nondestructive sustained yield harvesting of resources such as wild-harvested fruits is to play its suggested important role in tropical forest conservation, much stronger efforts will be needed to prevent destructive overharvesting of these potentially significant resources.

Tree species richness of upper Amazonian forests.

Upper Amazonian data for tree species richness in 1-hectare plots are reported. All plants >/=10 cm diameter were censused and identified in six plots in Amazonian Peru and one on the Venezuela-Brazil border. The two plots from the everwet forests near Iquitos, Peru, are the most species-rich in the world, with approximately 300 species >/=10 cm diameter in single hectares; all of the Peruvian plots are among the most species-rich ever reported. Contrary to accepted opinion, upper Amazonian forest, and perhaps Central African ones, have as many or more tree species as comparable Asian forests. Very high tree species richness seems to be a general property of mature lowland evergreen forests on fertile to moderately infertile soils on all three continents.

Deforestation and increased flooding of the upper Amazon.

The height of the annual flood crest of the Amazon at Iquitos has increased markedly in the last decade. During this same period, there has been greatly increased deforestation in the upper parts of the Amazon watershed in Peru and Ecuador, but no significant changes in regional patterns of precipitation. The change in Amazonian water balance during the last decade appears to be the result of increased runoff due to deforestation. If so, the long-predicted regional climatic and hydrological changes that would be the expected result of Amazonian deforestation may already be beginning.