沿海沙地厚荚相思和木麻黄凋落叶分解及养分释放

采用野外分解网袋法对沿海沙地9年生厚荚相思（Acacia crassicarpa）和木麻黄（Casuarina equisetifolia）林分凋落叶的分解速率和养分释放进行了研究。结果表明:厚荚相思和木麻黄凋落叶6-8月分解速率最快，但残留率差异不显著（p>0.05）。用Olson衰减指数模型推算分解50%和95%所需时间，厚荚相思为1.10 a和4.73 a，木麻黄为1.14 a和4.93 a。2种凋落叶N、P和Ca元素在分解末期的质量分数均高于初始质量分数，C、K和Mg均低于初始质量分数。凋落叶分解速率与C、Mg初始质量分数、C/N和C/P比呈极显著负相关（p<0.01），与N、P初始质量分数呈极显著正相关，与K质量分数呈显著负相关（p<0.05），与Ca初始质量分数呈显著正相关。在滨海沙地2种凋落叶各营养元素在分解末期均表现出释放特征，厚荚相思凋落叶养分总释放率K>Mg>C>Ca>N>P，木麻黄则为Mg>K>C>Ca>N>P。厚荚相思凋落叶N、P质量分数高，养分净释放相对较多，可以作为改造沿海沙地木麻黄纯林的混交树种。

Decomposition Dynamics and Nutrient Release of Leaf Litters for Acacia crassicarpa and Casuarina equisetifolia Forests in Southeast Coastal Area,China

Litter decomposition and nutrient release of 9-year-old Acacia crassicarpa and Casuarina equisetifolia plantations on a sandy coastal plain soil in southeast Fujian Province from November 2011 to October 2012 were examined using the litter bag method. The fastest decomposition rates of the two leaf litters were found in June to August. However, differences in residual rate were not significant (p>0.05). The analysis of Olson’s exponential decay model showed that it would cost for about 1.10 and 4.73 years to decompose 50% and 95% of A. crassicarpa leaf litter, and to decompose 50% and 95% of C. equisetifolia leaf littler, the time would be 1.14 and 4.93 years. In the late stage of litter decomposition, the contents of the nitrogen (N), phosphorus (P) and calcium (Ca) increased with time, while the contents of carbon (C), potassium (K) and magnesium (Mg) decreased. Release dynamics of nutrients differed in two forest types in different decomposition periods. The litter decomposition rate was significantly and negatively correlated to the initial C, Mg contents and the ratios of, C/N and C/P (p<0.01), and significantly and positively correlated to K content (p<0.05). The orders of releasing speeds of leaf litters were K>Mg>C>Ca>N>P for A. crassicarpa, and Mg>K>C>Ca>N>P for C. equisetifolia plantation. The A. crassicarpa had higher nutrient release rate in leaf litter, and it was more appropriate to be mixed with C. equisetifolia.