土壤水分含量和凋落物特性对陌上菅细根和叶片凋落物分解的影响

凋落物分解是湿地生态系统中碳和养分循环的关键过程.对比叶片凋落物和细根的分解速率，有助于阐明水分变化条件下不同凋落物类型对湿地碳循环的相对贡献，提高人们对不同有机碳源分解驱动机制的理解.以安徽省升金湖湿地典型湿生植物——陌上菅（Carex thunbergii）为研究对象，采用分解袋法进行凋落物分解试验，分析叶片凋落物和细根在不同土壤水分含量（30%、50%和70%）下的分解动态.结果表明:①经过5个月的分解，在30%、50%和70%的土壤水分含量下，陌上菅的细根质量残留率分别为46.7%、58.1%和60.1%，叶片凋落物的质量残留率分别为37.9%、31.6%、33.9%.②在30%、50%和70%的土壤水分含量下，陌上菅的细根分解速率常数分别为1.78、1.27、1.12，叶片凋落物的分解速率常数分别为2.56、2.94、2.54，且它们之间存在显著性差异（P < 0.05）.③细根的分解速率与土壤水分含量之间呈负相关（P < 0.001），而叶片凋落物的分解速率与土壤水分含量呈正相关（P=0.01）.④根据重复测量方差分析结果可知，凋落物分解受凋落物类型、分解时间及二者交互作用的影响，且凋落物类型是主导因素.分别对细根和叶片凋落物的质量损失进行重复测量方差分析，发现在细根的分解过程中，土壤水分含量是主要影响因素，而在叶片凋落物分解过程中，分解时间是主导因素.研究显示，相同土壤水分含量下，叶片凋落物的分解速率比细根快；湿地水位变化条件下，土壤水分含量对细根和叶片凋落物分解具有不同的影响，土壤水分含量的增加促进了叶片凋落物的分解，但对细根的分解产生了抑制作用. 

Effects of Soil Moisture Content and Litter Quality on Decomposition of Carex thunbergii Fine Roots and Leaf Litter

Litter decomposition is a key process of carbon and nutrient cycling in wetland ecosystems. Comparing the decomposition rate of leaf litter and fine roots is helpful to clarify the relative contribution of different litter types to wetland carbon cycle under the condition of water change, and improve our understanding of the decomposition driving mechanism of different organic carbon sources. The decomposition dynamics of leaf and fine root litters of Carex thunbergii, a typical wetland plant in the Shengjin Lake Wetland, Anhui Province, were studied using the litterbag method under different simulated soil water contents. The results showed: (1) After 5 months of decomposition, under soil moisture content of 30%, 50% and 70%, the mass remaining for fine roots of C. thunbergii was 46.7%, 58.1% and 60.1%, and the mass remaining for leaf litter was 37.9%, 31.6% and 33.9%, respectively. (2) Under soil water content of 30%, 50% and 70%, the decomposition rate constants for fine roots were 1.78, 1.27 and 1.12, respectively, and for leaf litter were 2.56, 2.94 and 2.54, respectively, and there were significant differences between various soil water contents (P<0.05). (3) The mass loss of fine roots was negatively correlated with soil water content (P<0.001), and the positively correlated with leaf litter (P=0.01). (4) The results of repeated-measures ANOVA show that the decomposition of litters was affected by the litter type, decomposition time and their interaction, with litter type being the dominant factor. When analyzing fine roots and leaf litter separately, soil moisture content significantly affected the decomposition of fine roots, while the decomposition process of leaf litters was mainly influenced by retrieval time. Overall, the decomposition rate of leaf litter was faster than that of fine roots under the same soil moisture content. Soil moisture content differentiated the decomposition of fine roots and leaf litter in a wetland ecosystem with fluctuating groundwater table. The increase of soil water content promotes the decomposition of leaf litter, but suppresses the decomposition of fine roots.