高寒森林不同生境凋落叶分解过程中水溶性组分动态特征

凋落叶分解所产生的水溶性组分(water soluble matter)是森林水陆不同生境碳和养分迁移的重要载体。本研究通过布设高寒森林4种代表物种凋落叶分解袋,即康定柳(Salix paraplesia)、高山杜鹃(Rhododendron lapponicum)、方枝柏(Sabina saltuaria)和四川红杉(Larix mastersiana),探讨其在林下地表、溪流和河岸带3种生境下不同分解时期(冻结初期、冻结期、融化期、生长季节、生长季节后期)的水溶性组分及水溶性碳含量动态及其影响因素。结果表明:经两年的分解,发现溪流显著促进了凋落叶中水溶性组分和水溶性碳的释放;同一物种凋落叶在不同生境下水溶性组分和水溶性碳损失差异显著(P<0.05),整体表现为溪流>河岸带>林下;在分解初期水溶性组分含量有明显的降低;在整个分解过程中,水溶性组分(-70.43%)和水溶性碳(-84.31%)含量变化基本一致且呈明显降低趋势。此外,凋落叶中水溶性组分和水溶性碳的释放速率受时间、物种以及区域环境因子(温度、p H值、营养成分)的调控。这些结果表明,高寒森林凋落叶中水溶性组分和水溶性碳在分解过程中易随水体的流动而转移至下游生态系统,并且区域环境因子在凋落叶水溶性组分和水溶性碳释放过程中具有重要的作用,这为深入理解高寒森林以凋落物为载体的物质迁移过程提供了科学依据。

Dynamics of water-soluble matters during leaf litter decomposition under different habitats in an alpine forest.

Water-soluble matter(WSM)released during litter decomposition is an important source of carbon and nutrient in different forest aquatic and land habitats.Using litterbag method,leaf litter decomposition of four dominant species(i.e.,Salix paraplesia,Rhododendron lapponicum,Sabina saltuaria,and Larix mastersiana)was examined in an alpine forest.We investigated the dynamics of WSM and water soluble carbon(WSC)contents and their related influencing factors during litter decomposition in stream,riparian zone,and forest floor at different periods(i.e.,pre-freezing period,freezing period,melting period,growing season,and late growing season).After two years of decomposition,we found that stream significantly promoted the release of WSM and WSC in leaf litter.The losses of WSM and WSC contents of the same litter species were significantly differed among different habitats(P<0.05),with stream>riparian zone>forest floor.The content of WSM decreased remarkably at the initial stage of decomposition.Across the whole decomposition process,changes in the contents of WSM(-70.43%)and WSC(-84.31%)showed a similar decreasing trend.In addition,the releases of WSM and WSC during leaf litter decomposition were significantly affected by decomposition period,litter species,and local environmental factors such as temperature,p H,and nutrient availability.These results suggested that WSM and WSC in decomposing leaf litter were easy to transfer to the downstream ecosystems with water flow.Environmental factors played an important role in the release of WSM and WSC during leaf litter decomposition,which provided useful information for our better understanding of material fluxes in alpine forests.