Dynamics of plant organic matter decomposition in different agricultural landscapes

ABSTRACT The functioning of ecosystems or agroecosystems is mainly dependent on the soil-litterfall interaction. Thus, the objective of this work was to evaluate the effect of different soil use and management systems on the dynamics of decomposition of plant residues of Azadirachta indica (neem) and Gliricidia sepium (gliricidia). The study was conducted in four land occupation systems, namely: remaining forest, agroforestry, agricultural mandala, and pasture. The decomposition rate was estimated using nylon bags (litter bags), containing 20 g of leaves of A. indica and G. sepium, which were arranged on the soil surface of each area for 18, 36, 54, 72, 90, and 108 days. A completely randomized design was used for each species, considering each area as one treatment, with four replications for each collection. The data were subjected to regression analysis and the means were compared by the Tukey's test (p<0.05). More than 85% and 90% of A. indica and G. sepium plant matters, respectively, had been decomposed after 108 days, regardless of the system evaluated, denoting that these species present high decomposition rates. The phytomass half-life time varied from 16 to 23 days for G. sepium and from 25 to 37 days for A. indica, depending on the land use system. Edaphic temperature, soil water content, and leaf physical and chemical characteristics are weight loss predictors. The results provide important information to enable forest management practices.

摘要 生态系统或农业生态系统的功能主要依赖于土壤-凋落物交互作用。因此，本研究旨在探讨不同土壤利用与管理系统对印楝（Azadirachta indica）和格利西迪亚（Gliricidia sepium）植物残体分解动态的影响。本试验在四种土地利用系统中开展，分别为原生林、农林业、农业曼陀罗系统和牧场。本研究采用尼龙袋（凋落物袋，litter bags）法估算分解速率，每个袋子装载20克印楝和格利西迪亚的叶片，将其放置于各试验区域的土壤表面，分别于18、36、54、72、90和108天后回收。针对两个物种均采用完全随机设计，以每个区域作为一个处理组，每次采样设置4次重复。对试验数据进行回归分析，并采用Tukey检验进行均值比较（p<0.05）。无论采用哪种土地利用系统，在108天后印楝和格利西迪亚的植物残体分解率分别超过85%和90%，表明这两个物种均具有较高的分解速率。格利西迪亚的植物生物量半衰期为16~23天，印楝为25~37天，具体数值取决于土地利用系统类型。土壤温度、土壤含水量以及叶片的理化特性是植物残体质量损失的关键预测因子。本研究结果可为森林管理实践提供重要的理论依据。