Geographic distribution of tree species diversity of the United States reveals positive association between biodiversity and site productivity.

摘要

With the loss of species worldwide due to anthropogenic factors, especially in forested ecosystems, it has become more urgent than ever to understand the biodiversity-ecosystem functioning relationship (BEFR). BEFR research in forested ecosystems is very limited and thus studies that incorporate greater geographic coverage and structural complexity are much needed. Here, I compiled ground-measured data from 436,177 Forest Inventory and Analysis (FIA) plots of every U.S. state except Hawaii to map current basal area, site productivity, and tree species diversity across the United States. Based on these point-data maps, I investigated the relationship between forest productivity and tree species diversity. Out of 15 forest types, 13 show a positive association between diversity and productivity, and only two show insignificant or negative relationships. The large number of ground-measured plots, as well as the magnitude of geographic scale, rendered overwhelming evidence in support of a positive tree species diversity-timber productivity relationship. This empirical evidence provides insights to forest management and biological conservation that are of a much broader applicability than controlled experiments in terms of both forest type and geographic scale. The findings imply that timber productivity across the United States may be impaired by the loss of species in forested ecosystems, and that biological conservation, due to its potential benefits on maintaining productivity, can have profound impacts on the availability of selected services from forested ecosystems.