水淹条件下灰化薹草和虉草活体、枯落物分解过程的比较

为了揭示鄱阳湖湿地活体植物和自然枯落物在水淹条件下分解过程的差异,以鄱阳湖湿地优势植被物种灰化薹草(Carex cinerascens)和虉草(Phalaris arundinacea)为研究对象,采用分解袋法开展室内模拟实验。植物样品设置新鲜和风干两种处理,分别模拟活体植物和自然枯落物在水下的分解过程。研究结果表明:(1)在180 d的淹水实验过程中,两种处理下的灰化薹草和虉草的分解过程都具有阶段性,前期分解速率较快,后期较慢。(2)两种植物枯落物的分解速率与植物C/N比有显著相关性,而活体植物的分解速率与植物C/N比相关性不强。(3)活体植物和自然枯落物的水下分解速率与物种有关,虉草活体比虉草枯落物分解速率快,而薹草活体比薹草枯落物分解速率慢。(4)模拟实验结束时活体植物仍有34%—43%未分解,推测鄱阳湖丰水期退水后大量洲滩植被消失的原因并非是植被在水淹下完全分解,而是一部分植被被水生动物啃噬或被水流冲走。

A comparative study on the underwater decomposition of live and dried Carex cinerascens and Phalaris arundinacea

To reveal the difference in the rates of underwater decomposition between living plants and litters in Poyang Lake wetland, this study was conducted involving a microcosm experiment with two predominant species-Carex cinerascens and Phalaris arundinacea-using the litter bag method. Fresh and dried plant samples were prepared to simulate the decomposition processes of living plants and natural litters, respectively. The results showed that:(1) The decomposition process of both plants (C. cinerascens and P. arundinacea), lasting 180 days, had a quick primary stage and a slower later stage. (2) The decomposition rates of both litter samples were significantly correlated with their C/N ratios, but similar correlation was not found in the living samples. (3) The underwater decomposition rate was related with the species; the living P. arundinacea decomposed faster than its litters, while living C. cinerascens decomposed slower than its litters. (4) At the end of the experiment, 34%-43% of the living plants remained undecomposed. We speculated that aquatic erosion and foraging by animals had important contribution to the disappearance of large plants after the lowering of water levels in the Poyang Lake wetland.