Comment on "Ecosystem Properties and Forest Decline in Contrasting Long-Term Chronosequences"

Abstract

Wardle et al. (1) report that forest decline is associated with increased P limitation relative to N and a reduced release of P from decomposing litter. Geochemical changes in soil phosphorus fractionation during long-term soil development have been well established (2). Subsequent biogeochemical studies using the Hawaiian Islands as a model system have proven the shift of N limitation in net primary productivity in the developing phase to P limitation in the retrogressive phase (3–5). However, the decline of soil P availability cannot necessarily be translated to ecosystem processes elsewhere (6). I argue that the rise and decline of forest biomass is peculiar only to the biomes where regional tree-species diversity is impoverished. Unlike the Hawaiian model and the forest ecosystems studied in (1), conspicuous forest decline does not occur in the mainland tropics.