Abstract:

To study the monthly dynamics of forest leaf litterfall, the leaf litters of 7 forests in Pingxiang of Guangxi were collected and their chemical components (N, P, K, Ca and Mg) were determined during the period from May of 2006 to April of 2007 The results indicated that the monthly variations of leaf litter's nutrient contents of N, P, K, Ca and Mg in leaf litters from seven standshad common trends. The contents of N and P in the leaf litterfall were high, while the content of K was low in the rain season (from April to September) when the temperature was high and trees grew vigorously. By contrast in the dry season (from October to next March) when the temperature was low and trees grew slowly or was in dormancy, the concentration of K was high, and the contents of N and P were low in the leaf litterfall. It suggested that N and P concentrations in the leaf litterfall were positively related to growth of tree, whereas the concentration of K in foliage litter was negatively related with the trees growth. The content of Ca was stable all the year within a forest, however it varied significantly from one stand to another. The monthly variation of Mg in leaf litterfall fluctuated significantly. The leaf litterfall's nutrient contents of different forests varied greatly. The highest content of N (14.44 g·kg^-1) occurred in Betula alnoides plantation and the lowest N (5.11 g·kg^-1) in Michelia macelureiplantation, the highest P (1.20 g·kg^-1) in the secondary natural forest and the lowest P (0.53 g·kg^-1) in Pinus massoniana plantation. Like to P, the highest of K was in the secondary natural forest with 5.16 g·kg^-1 and the lowest in Pinus massoniana plantation with 1.71 g·kg^-1. Ca of leaf litterfall in Cunninghamia lanceolata plantation was the highest (11.10g·kg^-1), and that in Pinus massoniana plantation was the lowest with 3.76 g·kg^-1. Mg of leaf litter fall in the secondary natural forest was 3.03 g·kg^-1 (highest), and that in Pinus massoniana plantation was 1.18 g·kg^-1 (lowest). Among the 7 experimental forests, the ratio of the highest content to the lowest content of every nutrient in the leaf litterfall was more than two.

Key words: southern subtropics, leaf litterfall, nutrient concentration