Factors influencing decomposition of leaves for five plant species at El Verde

We evaluated the influences of leaf quality, climate and microsite on the decomposition of leaves of five tropical tree species. Single-species litterbags were used to determine weight loss during the first three months of decomposition in the Luquillo Experimental Forest, Puerto Rico. Significant differences were found in decomposition rates among leaf species (Inga fagifolia &lt; I. vera &lt; Manilkara bidentata &lt; C-roton poecilanthus &lt;&lt; Sapium laurocerasus), but only S. laurocerasus differed significantly from the other species. Lignin had a suggestive negative correlation with leaf decomposition while carbon content and the lignin:N ratio were significantly correlated with mass loss. Content of N, P, Ca, and polyphenol were not significantly correlated with mass loss, but several of the litter quality variables were correlated with each other. Leaf species decomposed faster under canopies of their source trees than in a common plot where the source species were absent. Decomposition in two species in the Euphorbiaceae, S. laurocerasus and C. poecilanthus, was significantly affected by microsite. Leaching losses during the first three weeks were greater under source trees than in the common plot, and may have been associated with differences in canopy structure and throughfall. Differences in detrital communities, however, could have contributed to the differences in decomposition between microsites. Leaves of all species decomposed significantly faster in the wet than in the dry period (P = 0.001) despite little climatic variation in this subtropical wet forest type. This suggests that decomposition of tropical leaf litter might be sensitive to microclimatic changes on the forest floor resulting from either global climate change, or from natural or anthropogenic disturbances that open the canopy. Support for this work was provided by grants BSR-8811902, DEB-9411973, DEB-9705814 , DEB-0080538, DEB-0218039 , DEB-0620910 , DEB-1239764, DEB-1546686, and DEB-1831952 from the National Science Foundation to the University of Puerto Rico as part of the Luquillo Long-Term Ecological Research Program. Additional support provided by the University of Puerto Rico and the International Institute of Tropical Forestry, USDA Forest Service.本研究评估了叶片品质、气候及微生境对五种热带树木叶片分解过程的影响。实验于波多黎各卢奎洛实验森林（Luquillo Experimental Forest）开展，采用单物种凋落袋法测定分解前三个月的叶片重量损失情况。结果显示，不同树种的叶片分解速率存在显著梯度差异（细脉印加树<em>Inga fagifolia</em> < 维拉印加树<em>I. vera</em> < 双齿曼密木<em>Manilkara bidentata</em> < 变叶巴豆<em>Croton poecilanthus</em> << 月桂叶乌桕<em>Sapium laurocerasus</em>），且仅月桂叶乌桕（S. laurocerasus）与其余树种存在显著差异。木质素含量与叶片分解速率呈提示性负相关趋势，而碳含量及木质素氮比（lignin:N）则与叶片重量损失呈显著相关关系。氮、磷、钙及多酚含量与叶片重量损失无显著相关性，但部分凋落物品质指标间存在显著相关性。各树种叶片在其源树冠层下的分解速率快于不存在源树的对照样地。大戟科（Euphorbiaceae）的两个树种——月桂叶乌桕与变叶巴豆的分解过程受微生境影响显著。前三周的淋溶损失在源树冠层下高于对照样地，这可能与冠层结构及穿透雨的差异有关。但碎屑群落的差异同样可能导致不同微生境下分解速率的差异。尽管该亚热带湿润森林的气候变异极小，但所有树种的叶片在湿季的分解速率均显著快于干季（P=0.001）。该结果表明，热带叶片凋落物的分解过程可能对林地表层微气候变化极为敏感，而此类变化可由全球气候变化或林冠开启的自然/人为干扰引发。 本研究的资助来自美国国家科学基金会（National Science Foundation）拨付给波多黎各大学的多项项目经费（BSR-8811902、DEB-9411973、DEB-9705814、DEB-0080538、DEB-0218039、DEB-0620910、DEB-1239764、DEB-1546686、DEB-1831952），相关工作属于卢奎洛长期生态研究计划（Luquillo Long-Term Ecological Research Program）的一部分。本研究同时得到波多黎各大学及美国农业部林务局国际热带林业研究所的额外资助。