高山森林溪流凋落叶冬季水溶性碳含量动态

凋落物分解过程中水溶性碳是高山森林溪流生态系统碳的重要来源,其在溪流中的流动转移不仅会影响下游水质环境,而且其含量动态受冬季季节性雪被形成及消融过程的深刻影响,但缺乏必要关注.因此,采用凋落叶分解袋法,以川西高山森林典型乔木(四川红杉Larix mastersiana、方枝柏Sabina saltuaria)和灌木(高山杜鹃Rhododendron lapponicum、康定柳Salix paraplesia)凋落叶为研究对象,根据凋落叶自然分解规律,研究冬季不同时期(冻结初期、冻结期、融化期)河流、溪流、河岸带以及林下凋落叶水溶性碳以及可溶性组分含量格局的动态变化特征.结果表明:在冬季的分解过程中,冻结初期河流与溪流中凋落叶水溶性碳与可溶性组分含量显著降低,而至冻结期与融化期含量均无明显变化.各时期,林下凋落叶水溶性碳和可溶性组分含量显著高于其他生境,表现为从河流、溪流、河岸带至林下逐渐增加的变化趋势.相关分析表明,高山森林凋落叶分解过程中水溶性碳和可溶性组分含量与平均温度、正积温、负积温以及流速均呈极显著负相关关系,同样也受到PO3-4和p H等水环境因子的影响.可见,高山森林凋落叶冬季水溶性碳和可溶性组分在分解过程中易随水体的流动而向下游生态系统输出,这为深入认识高山森林-流域水体间的生态联系提供了一定的科学依据.

Dynamics pattern of dissolved carbon content during foliar litter decomposition in winter in alpine forest streams

Litter dissolved carbon is one of the primary material resources in alpine forest stream ecosystem. The flux of dissolved carbon from litter to stream water can essentially affect water quality of downstream, but the dynamic of litter dissolved carbon could be regulated by forming and melting of seasonal snow cover in winter. However, little information has been available on the dynamics of litter dissolved carbon in winter in alpine forest streams. In order to explore the dynamic characteristics of the water soluble components and total dissolved carbon during foliar litter decomposition in winter, a field experiment using litterbag method was conducted in an alpine forest in Western Sichuan. The foliar litter of two dominant canopy trees (Sabina saltuaria, and Larix mastersiana) and two shrubs (Salix paraplesia and Rhododendron lapponicum) were selected. The litterbags were placed in a headwater stream, river, riparian zone and closed canopy, and sampled in different freezing-thawing periods of winter (pre-freezing period, freezing period and thawing period). The results indicated that the total dissolved carbon and water soluble components of litter were significantly reduced in pre-freezing period in the river and stream, while few obviously changes were detected in freezing period and thawing period. The total dissolved carbon and water soluble components were obviously higher under the closed canopy than in the other habitats in each periods, displaying the order as river< stream< riparian zone< closed canopy. In addition, the dynamics of total dissolved carbon and water soluble components content in litter showed significant negative correlation with average temperature, positive accumulated temperature, negative accumulated temperature and water flow velocity, and were impacted by pH, PO₄^3-and other water characteristics during litter decomposition in winter in this alpine forest. The results implied that total dissolved carbon and water soluble components in litter can easily enter the downstream ecosystem with water flowing, which could further provide some scientific basis in understanding the ecological relationship between alpine forest and water basin.