关键词: 喀斯特, 凋落物, 养分含量, 养分归还, 原始林

Abstract: Litterfall is metabolic product of a forest during its growth, and plays an important role in recycling of matter and energy. In this study, based on the observations of litterfall in a virgin forest in the Maolan Karst region, southwest China during the yearperiod from September 2007 to August 2008, analysis was done for monthly dynamics of total litterfall, amount of each component (leaves, branches, reproductive organs and others) of the litterfall, nutrient contents in each fraction and amount of nutrient recycled. Results show that evergreen and deciduous broad-leaved mixed forest displayed two peaks in monthly variation of litterfall, appearing in September – January and April. The annual litterfall was 6.9 t· hm^-2, of which with leaves, branches, reproductive organs, and others accounted for 71.0%, 15.9%, 1.5%, and 11.6%, respectively. Nutrients in the litters were mainly C, Ca and N, which did not have any apparent law in monthly dynamics. Annual nutrients recycled with litterfall exhibited  a decreasing order of: C ＞ Ca ＞ N ＞ Mg ＞ K ＞ P, which differing from the one (C ＞ N ＞ Ca ＞ K ＞ Mg ＞ P) in forests in non-Karst regions. Nutrient contents varied from fraction to fraction of the litterfall. Branches were relatively low in N, Mg, P and K, while the other fractions were relatively high in C, N, P and Mg, and reproductive organs were relatively low in C, N, and Ca. The Ca and Mg contents in the litterfall and the amounts of Ca and Mg recycled were much higher than those in common forests in non-karst regions, while the K content in the litterfall and K amount recycled was lower in the former than in the latter, suggesting that K deficiency is probably the major factor limiting growth of the vegetation in karst regions.

Key words: Karst, litterfall, nutrient contents, nutrient recycled, virgin forest