三江平原典型湿地枯落物早期分解过程及影响因素

枯落物分解是湿地物质循环和能量流动的关键环节,是维持湿地功能的重要过程之一。采用分解袋法对三江平原3种典型湿地植物枯落物分解过程及影响因素进行了研究。研究表明,在164d实验过程中乌拉苔草分解速率始终最快;在分解前103d中毛果苔草分解速率大于小叶章,但在103~164d间小叶章分解速率大于毛果苔草;分解164d,小叶章、乌拉苔草和毛果苔草枯落物的失重率分别为初始重的31.98%、32.99%和28.91%。分解过程中小叶章和毛果苔草枯落物中有机碳浓度波动较大,而乌拉苔草枯落物中持续下降;3种枯落物有机碳绝对含量都表现为净释放。小叶章枯落物中N浓度波动较大,绝对含量发生净释放;毛果苔草枯落物N浓度持续增加,绝对含量净增加;乌拉苔草枯落物N浓度先增加后减少,绝对含量发生净释放。3种枯落物中P浓度都先迅速下降后缓慢上升,绝对含量都表现为净释放。3种枯落物中C/N和C/P也相应的发生变化。小叶章和乌拉苔草枯落物分解速率与枯落物C/P显著相关,而毛果苔草枯落物与枯落物N浓度显著相关;对应3种枯落物分解速率的主要环境因子分别为土壤含水量、土壤容重和土壤温度。3种枯落物分解速率和营养物质含量动态受到枯落物自身质量和温湿条件、周围环境营养状况等自然环境条件的共同影响,相比而言,受枯落物质量的影响更大。

The early-stage litter decomposition and its influencing factors in the wetland of the Sanjiang Plain, China

Litter decomposition is a key step to the nutrient cycle and energy flow in wetlands. It is also an important process in maintaining wetland functions. Using the litter bag technique, this paper examines the decomposition rates and their influencing factors by investigating three wetland macrophytes in the Sanjiang Plain, Northeast China: Calamagrostics angustifolia, Carex meyeriana, and Carex lasiocapa. It was found that during the experiment period of 164 days, the litter of C. meyeriana had the highest decomposition rate, but the rates of the other two types of litter varied. From Days 1-103, the litter of C. lasiocapa had a higher decomposition rate than that of C. angustifolia, but this was reversed during Days 104-164. Such differences led to different weight losses after the 164 days: C. meyeriana lost 28.91 per cent of its weight, C. angustifolia lost 31.98 per cent and C. lasiocapa lost 32.99 per cent. Another finding was that the amount of organic carbon in the litter of C. angustifolia and C. lasiocapa fluctuated, but continuously decreased in that of C. meyeriana. However overall, all three types of litter released organic carbon. The N concentration fluctuated in the litter of C. angustifolia, but increased continuously in the litter of C. lasiocapa. C. meyeriana showed an increase in N concentration from Days 1-103, and a decrease during Days 103-164. N was released substantially from the litter of both C. angustifolia and C. meyeriana, but accumulated in the litter of C. lasiocapa. In contrast to the variation in N concentrations, P concentrations in all three types of litter apparently decreased first and then slightly increased. Overall, P release was observed in all three types of litter. Finally, the C/N and C/P ratios varied significantly in the decomposition process. The litter decomposition rates of C. angustifolia and C. meyeriana were strongly related to their C/P values, while the decomposition rate of C. lasiocapa correlated strongly with the P content of its litter. This paper concludes that the main environmental factors influencing the decomposition rates were soil moisture, soil bulk and soil temperature. This experiment suggests that the decomposition rates and nutrient content variations were simultaneously influenced by the quality of the litter as well as environmental factors. However, in the Sanjian Plain, they were more strongly affected by the quality of the litter.