草原凋落物的分解及营养元素的释放和累积

草原凋落物的分解是草原生态系统物质循环的主要环节, 其中植物营养元素的释放和累积对退化草场恢复的进程和质量有着重要意义。本文从凋落物自身的性质、外部环境因素(生物及非生物因子)、混合效应等对凋落物分解速率的影响以及凋落物分解时植物营养元素的释放和累积两个方面论述了国内外对草原凋落物的分解及营养元素的生物地球化学行为的研究现状。一般情况下, 草原凋落物分解速率与凋落物自身的N、P、K等元素含量正相关, 与C/N、C/P、木质素、纤维素等的比值或含量值负相关, 而与周围环境中营养元素的组成及含量的关系不大。混合凋落物中不同种类凋落物的N、P含量及物种丰富度影响着非加性效应作用的效果。在凋落物分解过程中, 总体趋势表现为分解初级阶段对N的积累, 对P 和K的释放, 而对Na、Ca、Mg等营养元素来说, 随物种和根茎叶等部位的不同规律也不一样。凋落物中各元素的含量、凋落物分解阶段、物种类型、非加性效应、土壤环境等都是影响其营养元素释放和累积的因素。据此, 本文展望了草原凋落物未来可能的研究方向, 指出多因子的交互作用对草原凋落物分解的影响、凋落物混合分解机制探究、某些大量及微量营养元素的释放和累积可能是未来需要研究的重点。

Influencing Factors of Grassland Litter Decomposition and Nutrient Release and Accumulation

Litter decomposition is a main linkage of material cycle in grassland ecosystem. In the meantime, nutrient elements release and accumulation play an important role in the process of degraded grassland recovery. In this paper, we briefly reviewed the research progress of litter decomposition and the biogeochemical behaviour of nutrient elements in grassland at home and broad from two aspects: the main factors which affect litter decomposition rate, including the properties of litter, external environment (biological and non-biological factors) and mixture effects; the release and accumulation of plant nutrient elements when litter decomposes. Grassland litter decomposition rates, in common circumstances, are positively correlated with initial litter N, P and K, while negatively correlated with C/N, C/P, lignin and cellulose, and insignificantly correlated with the nutrients ambient.The effects of non-additive effects are dependent on N and P contents as well as litter diversities. In the process of litter decomposition, an overall trend shows that litter accumulates N while it releases K and P at the primary stage of decomposition whereas it shows no obvious regularity on the immobilization of Na, Ca and Mg for different parts or types of species. Different contents of each nutrient, different stages of decomposition, different types of species, non-additive and soil environment are the main factors that affect the nutrients release and accumulation. It can be concluded that the exploration of the interaction of factors, the mechanism in mixture decomposition, the release and accumulation of some major and trace nutrient elements will be research hotspots in the future.