黄土丘陵区不同植物凋落叶片的分解及养分释放特性

叶片凋落物的分解对生态系统的养分循环具有重要意义。刺槐、油松和柠条是豫西黄土丘陵区退耕还林时普遍采用的树种,高羊茅是该区分布广泛的建种草本植物。采用分解网袋法,对该区 4 种植物叶片凋落物一年内的分解特征及营养元素的释放规律进行研究。结果表明:1)柠条叶的分解率分别比刺槐叶、油松和高羊茅高8.86%、19.87%和13.18%,分解规律符合Olson 指数模型,分解速率为柠条叶>刺槐叶>高羊茅叶>油松叶。2)分解过程中 4 种凋落叶片的C/N、P含量持续降低,木质素含量缓慢增加,纤维素含量呈先增加后降低的变化趋势;不同凋落叶片分解过程中全C和全N含量的变化趋势存在差异。4 种凋落叶片的C、P元素属于直接释放模式,N元素属于富集—释放模式。3)凋落叶片的分解速率与总C含量、木质素含量和C/N均呈显著负相关关系(P<0.01),因此该地区凋落叶片的总C、木质素含量和C/N可以作为预测该地区凋落物分解的指标,凋落物叶片功能特征(比叶面积、厚度、硬度等)可能是影响其分解速率的重要因素之一。

Leaf decomposition and nutrient release characteristics of different plant species in the Loess Hilly region

The decomposition of leaf litter has important significance for nutrient cycling in ecosystems. Robinia pseudoacacia, Pinus tabulaeformis and Festuca arundinacea are commonly used species for returning farmland to forests in the Loess Hilly Region of western Henan, and Caragana korshinskii is a widely distributed herbaceous plant in this region.We studied the differences in decomposition characteristics of R. pseudoacacia, P. tabulaeformis, F. arundinacea and C. korshinskii leaf litter, using a nylon bag method. Leaf litter of F. arundinacea decomposed, respectively, 8.86%, 19.87% and 13.18% faster than litter of R. pseudoacacia, P. tabulaeformis and C. korshinskii. Leaf litter decomposition processes followed Olson’s exponential model. Decay rates for leaf litter of the 4 species ranked F. arundinacea>R. pseudoacacia>C. korshinskii>P. tabulaeformis. During the decomposition process, the C/N and P content the leaf litter of 4 litters species decreased gradually but the lignin content increased slowly, while the cellulose content initially increased and then decreased. Change with time in C and P concentration of decomposing leaf litter followed a ‘direct release’ model, while N concentration followed an ‘enrichment-release’ model. The concentrations of total C, and lignin and the C/N ratio were significantly, negatively correlated with decomposition rate of the leaf litters (P<0.01).Therefore, the concentrations of total C, lignin and C/N ratio in leaf litter samples could be used as decomposition indicators to predict litter decay rate in this region. We also noted that physical characteristics of leaf litter (specific leaf area, thickness, hardness, etc.) are additional factors with important effects on leaf litter decomposition rate.