Aims Litterfall plays an important role in linking aboveground and belowground processes in forest ecosystems. Nutrients absorbed by plants can be released to the soil and re-utilized by plants via litter decomposition. Although litterfall composition and dynamics have been widely studied in the past two decades, the relationship among litterfall, nutrient cycling and vegetation types is poorly understood. Therefore, we studied litterfall in evergreen broad-leaved forests (EBLF) to enrich our knowledge of the relationship.
Methods The research was conducted in Tiantong National Forest Park (29°52'N, 121°39'E, 200 m a.s.l), Zhejiang, East China. We chose secondary and young EBLF (Schima superba community), coniferous and evergreen broad-leaved mixed forest (Pinus massoniana+Schima superba community), coniferous forest (Pinus massoniana community) and shrubland (Lithocarpus glaber + Loropetalum chinense community) to represent forests at different degradation stages and mature EBLF (Castanopsis fargesii community) to represent reference climax forest. Productivity, composition, nutrient concentration and total nutrient amount of the litterfall were measured each month from November 2003 to October 2004. Litterfall traits were correlated with soil total N, total P, total inorganic N, N mineralization and nitrification rates.
Important findings Degradation of EBLF significantly reduced litterfall productivity from 13.03 Mg·hm^-2 in mature EBLF to 6.38 Mg·hm^-2 in shrubland, and significantly reduced N concentration in litterfall. In contrast, P concentration showed no consistent pattern. Total N and total P amounts returned via litterfall decreased significantly with degradation. Soil total N was positively correlated with annual litterfall productivity but not litter N concentration. Soil total P was positively correlated with both annual litterfall productivity and litter P concentration. Soil inorganic N was not correlated with either productivity or litter nutrient concentration. Soil N nitrification rate was positively correlated with annual litterfall productivity and total amounts of nutrients returned, but was not correlated with litter N concentration. Soil N was not correlated with any litterfall traits. These results suggested that, during degradation of EBLF, shifting of plant functional types and simplifying of community structure reduced the quality and quantity of litterfall to a low level and consequently reduced soil nutrient pools.