| The frozen rain and snow disaster occurring in the subtropical regions in China in the beginning of 2008, destroyed the evergreen broad-leaved forest, changed its stand structure and broke the balance of the forest ecosystem. In.the mountain of Jiulianshan,the trees of evergreen broad-leaved forest were seriously lodged,broken off,and stump turned.and formed a lot of nonnormal casts.It is urgent to recover and rebuild evergreen broad-leaved forest ecosystem, but how to strengthen the biodiversity conservation and recover ecological function were the main issues in degraded ecosystem of Jiulianshan. The methods for resolving these issues are related to the important research field of the litter decomposition and nutrient cycling. This study compared the litter input, composition and decomposition rate, and nutrient release dynamics of several communities with different destroyed levels by the frozen rain and snow disaster in the evergreen broad-leaved forest of Jiulianshan. The data of the effects of frozen rain and snow disaster on the litter input and decomposition rate and nutrient content could provide the basic understanding of the mechanism of the forest nutrient cycling and forest ecosystems response due to global climate change, thus provide solutions to disaster recovery and reconstruction. The results were as follows:(1) The stand structural characteristics in several communities with different destroyed degree。 Although three sample plots with different affected levels were very close geographically, the important values of main tree species were different. The dominant tree species were still the Fagaceae, and Lauraceae. The tree density decreased with an increasement in the destroyed level. The density of adult trees in moderate affected community was about twice than that in seriously affected community. The average DBHs in all communities were different, but the average height was highest in P3 plot. Basal area were among 38.09～43.65 m2·hm-2 in different communities.(2) The litter input and compositionAnnual litter input in three sample plot was respectively 4116.95 kg·hm-2a-1 in P1 plot,2875.10 kg·hm-2a-1 in P2 plot, and 4 173.85 kg·hm-2a-1 in P3 plot. The corresponding proportions of leaf litter amount were 64.05%,61.81%,57.74% respectively. Leaves were the main parts of litter. The other components of litter were different in different plots.(3) The seasonal dynamics of litter inputThe seasonal dynamics of litter were almost the same in communities with different damaged degree, and all of them had two peaks. The first peak appeared during March and April in a year, which are the beginning of rainy season. The second peak was during November and December. The least litter input was occurred in both January and August. The litter input dynamics of leaf was similar to that of total litter. The monthly variation of both twig litter and raffle were different among the different plots, without the obvious regularity.(4) The litter decompositionIn the non-gap habitats, a loss of litter weight in all the communities with different disaster levels had the same trend. Litters decomposed fast initially, and slow down after 130 day, and finally rose sharply after 180 days. In different habitats, gap habitat was more conducive to the decomposition of litter than non-gap habitat. The Olsen Index equation was adopted to simulate process of litter decomposition, and the fitting result was good with R2>0.8 (p<0.05).(5) The dynamics of main nutrient release in litter The trend of the main nutrient release were similar in all the communities with different damaged degree, but the change in nutrient content in P2 plots was the largest.In all three communities, the content of nitrogen (N) showed an increasing trend, but the content of phosphorus (P) fluctuated. Contents of potassium (K) and magnesium (Mg) showed a net release, and content of calcium (Ca) increased firstly, but decreased later. The release of N, P, and K, as well as those of Ca and Mg were released similarly in gap and non-gap habitats. They had the same variation trends.(6) The air-drying and drying effects on litter decompositionThe remaining rates of air-dried samples are higher than that of drying samples. Drying could promote leaf litter decomposition. The two different treatments had complex influence on nutrient elements, and need further study.
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