天童国家森林公园常见植物凋落叶分解的研究

LEAF LITTER DECOMPOSITION OF COMMEN TREES IN TIANTONG

选择天童地区常绿阔叶林及其退化群落常见植物种为对象 ,着重探讨分解速率和基质营养含量以及比表面积 (SpecificLeafArea ,SLA)的关系 ,并试图通过单独分解试验和混合分解试验的比较 ,从物种、功能群角度探讨凋落叶多样性和分解这一生态系统过程的关系 ,为深入研究常绿阔叶林常见植物种的营养策略、群落养分循环等奠定基础 ,也为植被恢复、森林生态系统管理提供理论依据。结果表明 :所有凋落叶随时间进程失重率增大 ,但失重率并不与时间呈线性相关 ;凋落叶分解后N、P均发生了变化 ,大多数凋落叶在分解初期N、P均发生了积累 ,营养元素的释放和富集与凋落叶初始营养状况无明显的相关性。凋落叶的年分解系数与凋落叶中的初始N含量有较高的相关性 ,而与初始P含量则无显著的相关性 ;凋落叶的分解速率与成熟叶的面积无相关性 ,而与其SLA有很强的相关性。通过模型分析 ,天童地区大多数常见树种凋落叶分解 95 %需 1～ 4年 ,平均是 2 .5 4年 ;分解率最高的物种为山鸡椒 (Litseacubeba) ,其值为 6 .2 80 ,最低的为黄丹木姜子 (Litseaelongata) ,其值为 0 .5 5 8。凋落物混合对分解有很大的影响 ,虽在初期对分解有阻碍作用 ,但长期是促进的。若不考虑功能群差异 ,则可得出多样性的增加有利于分解的结论。功能群数?

Leaf litter decomposition is a critical pathway of nutrient cycling in forests, and the spatial and temporal dynamics of leaf litter decomposition as well as the factors affecting decomposition, such as litter quality and climate, have been studied intensively. More recently, the possible consequences of global environmental change on litter decomposition have received considerable attention. However, little research on the factors influencing litter decomposition has been conducted in the broad-leaved evergreen forests of Eastern China. Therefore, we studied leaf litter decomposition and nutrient release dynamics of selected plant species in the subtropical broad-leaved evergreen forests at Tiantong in Zhejiang Province by using a litter bag method. Results showed that litter mass and N and P concentrations in the decomposing leaf litter changed greatly with time. N and P concentrations increased in the initial decomposition stages for many species. Nutrient release or accumulation from the decomposing leaf litter was not correlated with the initial nutrient content of the leaf litter. Yearly decay rates of leaf litter were significantly correlated with the initial leaf litter nitrogen content but not with phosphorus content, and species with high nitrogen contents exhibited relatively faster decomposition rates. In addition, leaf area had little effect on decomposition, but there was a strong positive correlation between yearly decomposition rates and specific leaf area. Based on decomposition models, yearly decay rate ranged from 0.558 in Litsea elongata to 6.280 in L. cubeba. For most selected plant species, 95% decomposition rates ranged from 1-4 years, with an average of 2.45 years. Leaf litter composed of mixed species had a significant effect on decomposition patterns by inhibiting decomposition rates initially but accelerating rates during later stages. Dry weight loss of leaf litter increased with an increase of the number of species in the leaf litter mixture. Also, decomposition was accelerated by an increase in plant functional groups in the litter, but this effect gradually decreased as decomposition proceeded. The characteristics of species mix were the most important factor influencing decomposition. Overall, leaf litter decomposition is related to the initial quality of leaf litter, which includes structure and nutrient content of leaf litter, and the species composition of the mixed leaf litter.