亚热带森林降雨季节源头溪流非木质残体钙和镁储量动态特征

森林源头溪流是联系水陆生境的重要纽带,其非木质残体(凋落叶和<1 cm的小枝)所储存的钙、镁等养分动态直接或间接调控森林生态系统物质循环与迁移等生态过程。本研究以福建三明闽江流域上游集水区森林一条典型源头溪流为对象,于2021年雨季(3—8月)监测了该溪流中非木质残体钙和镁储量的动态特征。结果表明: 降雨季节该溪流单位面积非木质残体钙、镁总储量分别为178.1～890.5 mg·m^-2、13.8～61.6 mg·m^-2。雨季溪流单位面积的非木质残体钙、镁储量呈现出先增加后减少的动态变化,整体上表现为降低趋势,在各河段整体上存在显著差异,特别是溪流源头的储量显著高于其他河段。非木质残体钙、镁储量随降雨量的增加而显著增加,随溪流碱度、温度、溶解氧的增加而显著减少。河岸米槠林与针阔混交林等植被类型变化及有无支流汇入对非木质残体钙、镁储量没有显著影响。降雨季节森林源头溪流非木质残体的钙、镁总储量随时间推移整体上减少,主要受到降雨和溪流特征的共同调控。

Dynamics of Ca and Mg storage of non-woody debris in a subtropical forest headwater stream during the rainy season.

Forest headwater streams are the monumental cement for relating habitats of the terrene and water. Nutri-ent dynamics of non-woody debris in stream can directly and indirectly regulate the cycle and transport of forest nutrients, for example, Ca and Mg. In the rainy season (from March to August) of 2021, we monitored the dyna-mics of Ca and Mg storage of non-woody debris in a typical headwater stream in a subtropical forest. The results showed that total Ca and Mg storage of non-woody debris per unit area of stream ranged from 178.1 to 890.5 mg·m^-2 and 13.8 to 61.6 mg·m^-2 during the rainy season, respectively. The Ca and Mg storages of non-woody debris per unit area of stream during the rainy season displayed a pattern of first increase and then decrease, and overall a decrease pattern. The storage varied significantly among different sites, with higher values in stream source than others. The total Ca and Mg storage of non-woody debris positively correlated with precipitation, but negatively with stream water alkalinity, temperature, and dissolved oxygen. The variation of riparian forest type (e.g., Castano-psis carlesii forests or mixed coniferous forests) and with or without tributaries did not affect the storage of Ca and Mg in stream non-woody debris. During the rainy season, total Ca and Mg storage of non-woody debris in the headwater stream from forest generally decreased over time, which was mainly controlled by the characteristics of rainfall and stream.