中亚热带森林雨季源头溪流植物残体锰和锌储量动态特征

Dynamics of plant litter manganese and zinc storages in a middle subtropical forest headwater stream during the rainy season

植物残体不仅是森林源头溪流碳和养分的重要来源,也是森林重金属迁移的重要载体,其在源头溪流的动态特征能深刻影响森林及下游水域的生态功能,但缺乏必要的关注.以中亚热带森林源头溪流为研究对象,于2021年雨季(雨季前期3-5月、雨季后期6-8月)动态监测植物残体(叶和枝)锰(Mn)、锌(Zn)储量的时空动态特征,并探究其影响因素.结果表明:(1)源头溪流植物残体的Mn、Zn储量最大值均出现在雨季前期,最小值出现在雨季后期,在整个雨季叶的Mn、Zn储量分别减少了68.22%和64.06%,枝分别减少了60.26%和51.74%;(2)在空间上,植物残体叶和枝的Mn、Zn储量最大值均出现在溪流源头;溪流尽头河段相比于溪流源头河段,植物残体叶的Mn储量和Zn储量分别减少了79.60%、81.62%,植物残体枝的Mn储量和Zn储量分别减少了64.12%、73.18%,溪流总储量表现为输出模式;(3)Mn、Zn储量与降雨量、流速等环境因子显著正相关,与溪流水温、碱度、溶解氧、电导率等环境因子显著负相关.上述结果表明中亚热带森林源头溪流植物残体中的Mn、Zn储量在雨季输出,主要受到降水和溪流物理化学特征等因子的调控;因此森林源头溪流植物残体作为重金属的载体,具有一定净化水源的能力.

Plant litter is not only an important source of carbon and nutrients for forest headwater streams but is also an important carrier of forest heavy metals,whose dynamics in headwater streams can profoundly affect the ecological functions of forests and downstream waters.However,little attention has been paid to these processes.Taking a middle subtropical forest headwater stream as the study object,the spatial and temporal dynamics of Manganese(Mn)and Zinc(Zn)storage in plant litter(leaves and branches)were continuously monitored during the rainy season(early period:March to May;late period:June to August)in 2021,and the associated influencing factors were explored.The results showed that:(1)The maximum plant litter Mn and Zn storages during the raining season occurred in the early period,while the minimum values occurred in the later period,with leaf Mn and Zn decreasing by 68.22%and 64.06%,respectively,and those of branches decreasing by 60.26%and 51.74%,respectively;(2)Spatially,the maximum Mn and Zn storages of leaf and branch were found at the stream source,and their storages at the stream mouth decreased by 79.60%and 81.62%,respectively,for leaves,and decreased by 64.12%and 73.18%,respectively,for branches,compared with the stream source,indicating an overall output pattern;(3)Mn and Zn storages positively correlated with environment factors such as precipitation and flow velocity and negatively correlated with stream water temperature,alkalinity,dissolved oxygen,and electrical c onductivity.These fi ndings suggest that M n and Zn storage in plant litter in middle subtropical forest headwater streams shows an overall output pattern during the rainy season and is controlled by precipitation and the physical and chemical characteristics of the stream.Therefore,as carriers of heavy metals,plant litter in forest headwater streams can be used to purify water sources.These results provide the basic data for an in-depth understanding of the natural transport dynamics of forest metal elements.