几种水生植物腐解过程的比较研究

研究水生植物腐烂分解过程及其养分动态对认识水生态系统物质循环过程具有重要意义。通过室内植物分解模拟试验,对6种水生植物的腐解过程及腐解残余物成分的变化进行了比较研究。结果表明,在64 d的腐解过程中,浮叶植物的分解速率最快,沉水植物其次,挺水植物最慢;同种植物的分解速率及残余物成分变化在不同生物量密度组间存在一定差异,但总体趋势一致。分解过程中,植物残余物中P、纤维素、木质素含量的变化趋势种间差异较小,总体上P含量先迅速下降后缓慢上升,纤维素含量先下降后趋于稳定,木质素含量先上升后趋于稳定;植物残余物中C、N、半纤维素含量在分解初期种间的变化趋势不同,而分解后期则均为C含量上升,N、半纤维素含量趋于稳定。相关性分析结果表明,总体上,在整个分解周期中,初始N、P含量越大分解越快,初始纤维素、半纤维素、木质素含量、C/N、C/P、木质素/N等越大分解越慢;植物腐解不同阶段的质量指标对分解速率的影响有所不同,在分解前期,残余物中N含量越高分解越快,半纤维素含量、C/N、木质素/N越高,分解越慢,而后期木质素含量越高分解越慢,其它因子影响较小。

A comparative study on the decomposition processes among some aquatic plants

Studying decomposition processes and nutrient dynamics of aquatic plants is of great importance for better understanding of material cycles in aquatic ecosystems. In this paper, six aquatic plants (i.e., Phragmites australis, Zizania latifolia, Nelumbo nucifera, Nymphoides peltatum, Potamogeton crispus and Myriophyllum verticillatum) were chosen as the experimental materials. Using the mesh bag method, the decomposition processes and nutrient dynamics of the 6 aquatic plants was investigated in a laboratory environment for 64 days. Substantial differences in decomposition rates were observed among the 6 plants. The floating-leaved plants presented the highest decomposition rate, followed by the submerged and emerged plants in turn. For each plant, decomposition rate and residue composition varied by biomass density but had a similar temporal pattern. During the decomposition processes, the dynamics of phosphorus, cellulose and lignin contents showed the same variation trend across different plants. Phosphorus contents were decreased substantially in the first 4 days, followed by a slight increase. The phosphorus contents of the emerged plants was significantly lower than that of the floating-leaved plants and submerged plants during decomposition. Cellulose contents were decreased in the first 4 days and stabilized afterwards. The cellulose contents of the emerged plants was significantly greater than that of the floating-leaved plants and submerged plants during decomposition. Lignin contents were increased in the first place and then stabilized. Variation tends of carbon, nitrogen and hemicellulose contents in different plants' residues were different. The carbon contents of emerged plants kept stable at first, decreased then and increased at last. While the carbon contents of the floating-leaved plants and submerged plants fluctuated at first, decreased then and increased at last. The carbon contents of the submerged plants were significantly lower than that of the emerged plants and floating-leaved plants during decomposition. The nitrogen contents of the emerged plants increased slowly, while the nitrogen contents of the floating-leaved plants and submerged plants increased first, then decreased and settled out at last. The nitrogen contents of emerged plants were significantly lower than that of the floating-leaved plants and submerged plants during decomposition. The hemicellulose contents of the 6 plants settled out in the end of the decomposition, but they performed differently in the early stage of decomposition. The hemicellulose content of Phragmites australis settled out at first and then decreased. The hemicellulose content of Zizania latifolia increased first and then decreased. The other four plants' hemicellulose contents decreased first and then increased, and decreased at last. The hemicellulose contents of emerged plants were significantly greater than that of the floating-leaved plants and submerged plants during decomposition. Correlation analysis of decomposition rates and nutriment contents showed that the decomposition rates tended to be facilitated with increasing initial nitrogen, phosphorus contents; while the rates were slowed with increasing initial cellulose, hemicellulose, lignin contents and C/N, C/P, lignin/N. The main factors affecting the decomposition rates presented a temporal variation. In the early stage of decomposition, decomposition rates tended to be facilitated with increasing hemicellulose contents, C/N, lignin/N; while in the late stage, the rates were slowed with increasing lignin and the other factors played minor roles.