植物凋落物分解是全球碳收支的重要组成部分，也是养分循环的主要决定因素。在大多数湿地中，许多草本植物的地上部分枯萎之后并不会立即倒伏，而是持续一段时间保持“立枯”状态，成为残余物库的重要组成部分，而在这个阶段其分解过程已经开始。日前，中科院东北地理研究所湿地植物立枯分解研究取得进展，相关成果先后发表于《植物与土壤》和《Ecological Engineering》期刊。

科研人员以三江平原的主要湿地植物为研究对象，分析了植物地上凋落物在立枯期的分解过程。研究表明，湿地草本植物地上部分以立枯状态分解一年后，叶片和杆的质量损失分布达到19.3%~45.1%和14.3%~23.1%。在分解过程中，立枯植物的氮总量显著增加，但磷总量在一年后表现为净释放。因此，湿地草本植物凋落物在湿地生态系统碳和养分循环中起着重要作用。

该研究团队以沼泽化草甸的优势物种小叶章为研究对象，分析了凋落物在立枯和倒伏状态下分解过程的差异。研究表明，小叶章地上部分以“立枯”状态分解180天后质量损失很少，低于地表分解的相应组织，但分解一年后会超过或者接近在地表分解的相应组织。处于立枯状态的叶片和叶鞘在分解180天后养分残留量显著高于在地表分解的相应组织，但在分解360天以后，这种模式发生转变。此外，杆以立枯状态分解时的养分残留量一般高于其在地表分解时的养分残留量。（来源：中国科学报 彭科峰）

Comparing differences in early-stage decay of macrophyte shoots between in the air and on the sediment surface in a temperate freshwater marsh

Abstract  Litter decay is a fundamental process in ecosystem carbon flux and nutrient cycling. In wetlands, shoot litters on the sediment surface and in the air are important components of the detritus pool. We used the litterbag method to compare mass losses and nutrient dynamics of culms, sheaths, and leaves from Deyeuxia angustifolia on the sediment surface and in the air from October 2011 to October 2012 in a freshwater marsh in Northeast China. The mass losses for the three litters in the air were only approximately 3% and less than that on the sediment surface after 180 days of decay, but increased to 16–44% after one year of decay and thus exceeded or approached that of surficial corresponding litters. For leaves and sheaths, the increased nutrient (nitrogen and phosphorus) concentrations of aerial litters resulted in an approximately 10% increase in the nutrient amounts after 180 days of decay, which was greater than that of surficial corresponding litters; however, surficial litters exhibited a greater increase or a lesser decrease of nutrient amounts than did aerial corresponding litters after one year of decay. For culms, the litter nutrient amounts in the air were always more or not less than those on the sediment surface during one year of decay, although effects of the litter position on nutrient concentrations were negligible (for nitrogen) or varied over time (for phosphorus). Overall, the litter position significantly affected the decay processes in this marsh. Therefore, it is essential to consider litter mass and decay processes at different positions to comprehensively understand carbon cycle and nutrient turnover in temperate freshwater marshes.

原文链接：http://ac.els-cdn.com/S0925857415001305/1-s2.0-S0925857415001305-main.pdf?_tid=83623200-4aca-11e5-85e3-00000aacb35e&acdnat=1440467115_4c17296c51d2867e612b70a39fee8004