Conversion of a natural broad-leafed evergreen forest into pure and mixed plantation forests in a subtropical area: effects on nutrient cycling

Abstract

Conversion of natural broad-leafed evergreen forests into pure and mixed plantation forests in a subtropical area in China is a common practice in forest management. We investigated the effects of this conversion on litterfall, litter decomposition, and nutrient cycling. Monthly deposition of total N, P, K, Ca, and Mg through throughfall, stemflow, and various components of litterfall was investigated and compared over 3 consecutive years from January 1989 to December 1991 for both forests. The total annual fine litterfall over 3 years of observation was 4.8 t/ha in a pure plantation conifer forest of Chinese-fir (Cunninghamia lanceolata), 7.1 t/ha in a mixed plantation forest of Chinese-fir and Schima superba, and 13.3 t/ha in a natural broad-leafed evergreen forest of Castanopsis kawakamii, respectively. The contributions of litterfall to the total nutrient fluxes were greater than those of throughfall and stemflow for all five nutrient elements in two contrasting forests of Chinese-fir and C. kawakamii. The results of this study demonstrate that natural broad-leafed evergreen forest has a greater capability of nutrient return, coupled with higher rates of litter decomposition and nutrient release, larger soil nutrient pools, and higher nutrient availability, than pure forest, suggesting that conservation of a natural forest is a necessary measure for maintaining woodland soil quality and primary productivity.