Standing litter decomposition not only accounts for a considerable mass loss, but also plays an important role in nutrient cycling in wetlands. Anthropogenic activities have dramatically increased phosphorus (P) input into wetland ecosystems, which is likely to change the quality of macrophyte litters and influence the subsequent aerial decomposition. In this study, we determined the quality of senesced shoots (culms and leaves) from Deyeuxia angustifolia under different P treatments (Control, 0 g·m-2·a-1; P addition, 1.2 g·m-2·a-1) in a meadow in Sanjiang Plain, and measured their decomposition rates and nutrient release in the air. The aim of this study was to reveal the effects of increasing soil P availability on carbon (C) and nutrient cycling in the standing-dead phase. Phosphorus addition increased nitrogen (N) and P concentrations by 8.35% and 28.33%, respectively, in senesced leaves, but did not exert significant effects on culms (P>0.05). During the aerial decomposition, there were no obvious differences in mass loss rates and microbial respiration rates for both plant tissues between different P treatments (P>0.05). However, P addition caused an obvious decrease in nutrient remaining (in percentage terms) in decomposing leaves (P<0.05). Specifically, the N and P amount remaining in leaves from the P addition treatment were 106.64% and 49.34%, respectively, whereas that were 121.84% and 63.58%, respectively, from the control treatment after one-year aerial decomposition. In conclusion, P eutrophication would increase nutrient concentrations in senesced tissues from macrophytes, accelerating nutrient release during the standing-dead phase, and thus exert remarkable effects on nutrient cycling in freshwater marshes in Sanjiang Plain.%立枯分解是湿地植物凋落物分解的重要组成部分,在湿地养分循环中起着重要作用.在人类活动的影响下,磷大量流入到自然湿地中,可能会引起草本植物凋落物质量及立枯期分解过程的变化.通过磷添加控制试验(对照,0 g·m-2·a-1;磷添加,1.2g·m-2·a-1),探讨三江平原草甸中土壤磷可用性增加对优势植物小叶章(Deyeuxia angustifolia)地上部分(杆和叶片)凋落物质量及其在立枯期的分解过程的影响,以揭示磷可用性变化对植物立枯期碳与养分循环的影响.结果表明,磷添加引起叶片凋落物氮和磷含量的升高,升幅分别为8.35%和28.33%,但对杆凋落物无显著影响(P>0.05).在一年的立枯期内,来自于不同磷添加处理的凋落物质量损失速率及微生物呼吸速率无显著差异(P>0.05).然而,磷添加使立枯期叶片凋落物养分残留量(以百分比计)显著减少(P<0.05):分解一年后,来自于P添加处理的叶片凋落物氮和磷残留量分别为106.64%和49.34%,而对照处理分别为121.84%和63.58%.因此,在该地区的淡水湿地中,人类活动引起的磷富营养化将会通过提高植物组织的养分含量,改变其在立枯阶段的养分释放动态,从而对生态系统的养分循环产生重要影响.
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