长白山源头溪流河床凋落物的分布特征及季节动态

在北方寒冷区,凋落物于秋季大量输入溪流,是水生生物越冬生存的关键。河床凋落物的堆积和组成会直接影响凋落叶分解等关键生态过程,但目前国内关于北方地区溪流河床凋落物分布特征的研究匮乏。在长白山地区一条源头溪流,采用原位取样的方法,探究了溪流河床凋落物的分布特征及季节动态。结果表明:深潭型凋落物斑块的堆积面积和水深显著大于浅滩型凋落物斑块和倒木型凋落物斑块,流速则显著低于其他两种凋落物斑块;倒木型凋落物斑块的堆积厚度显著大于其他两种凋落物斑块。浅滩型凋落物斑块和倒木型凋落物斑块的组成以叶片为主,碎叶片次之,树枝树干最少;深潭型凋落物斑块的组成以碎叶片和树枝树干为主,叶片较少,但秋季和冬季冻结初期除外。冬季雪融期凋落物斑块的堆积厚度显著大于其他时期;春季凋落物斑块的堆积面积显著小于其他时期,水深显著大于其他时期。随着季节变化,浅滩型凋落物斑块中的叶片比例逐渐减少,碎叶片比例逐渐增加;深潭型凋落物斑块中的树枝树干比例逐渐增加。水深与浅滩型凋落物斑块中碎叶片的干重呈显著负相关。溪流内凋落物的分布具有时空差异性,可为寒冷区溪流生态过程后续的研究提供基础数据。

Distribution characteristics and seasonal dynamics of litter in a headwater stream bed of the Changbai Mountain

In northern cold regions,considerable litter flows into streams in autumn,which is critical to the survival of aquatic organisms in winter.The accumulation and composition of stream bed litter will determine the vital stream ecological process(e.g.,the decomposition of litter).Nevertheless,the research has been rarely conducted on litter distribution characteristics in stream beds in northern China.A headwater stream of the Changbai Mountain was taken as the research object.The distribution characteristics and seasonal dynamics of litter on the stream bed were determined with in-situ sampling method.The results were as follows.Pool type litter patches exhibited significantly larger accumulated area and water depth than those of riffle type litter patches and wood type litter patches,while their current velocity was noticeably less than those of the latter two types of litter patches.Wood type litter patches displayed significantly larger accumulated height than riffle type litter patches and pool type litter patches.Riffle type litter patches and wood type litter patches primarily consisted of leaves,followed by leaf fragments and the least branches and trunks.Except autumn and the pre-freezing period in winter,pool type litter patches were mainly composed of leaf fragments and branches and trunks,with fewer leaves.Litter patches in melting period in winter exhibited significantly larger accumulated height than in other periods.Litter patches in spring displayed significantly smaller accumulated area than in other periods,and the water depth displayed significantly larger than in other periods.The proportion of leaves in riffle type litter patches decreased progressively,and that of leaf fragments was elevated gradually.Pool type litter patches exhibited gradually increasing proportion of branches and trunks.Water depth displayed negative correlations with dry weight of leaf fragments in riffle type litter patches.The distribution of litter on the stream has spatial and temporal differences,which can provide a support for subsequent research on stream ecological processes in cold regions.