酸性沉降环境中森林生态系统的物质循环——树冠穿透水的水质及其形成机理

NUTRIENT CYCLES IN A FORESTED ECOSYSTEM UNDER ACIDIC DEPOSITION CIRCUMSTANCE THROUGHFALL CHEMISTRY AND ITS FORMATION

对林外降水和１８年生日本柳杉及日本扁柏的树冠穿透水中溶存元素浓度的系统测定表明：酸性降水在穿透树冠层时ｐＨ和溶存元素浓度有不同程度的升高，这种变化日本柳杉比日本扁柏更为明显。树冠穿透水中溶存元素量的增加主要来自干性沉降和树冠淋溶。采用多变量回归模型，以无雨期长短、降水量和降水酸度为自变量，以树冠穿透水溶存元素的净增加量为因变量对干性沉降和树冠淋溶量作了分离。研究结果基本说明了树冠穿透水的水质特性及其形成机理。

To clarify throughfall chemistry and its formation mechanism, measurements on nutrient concentrations were conducted for Japanese cedar and cypress throughfalls. Concentrations of most dissolved elements in throughfalls increased to 2～10 times compared to precipitation. Proton concentration,however,decreased to less than 1/3 of precipitation. Rainfree-duration and precipitation are significantly responsible for element net depositions in throughfalls, but showed different relations depending on elements. As determined by multiple regression analysis, percentages of wet deposition, dry deposition and canopy leaching of elements in throughfall are about 10%,20%,70% for K,20%,40%,40% for Ca and Mg,60%,30%,10% for Na,50%,10%,40% for NH 4-N,40%,30%,30% for Cl,40%,40%,20% for NO 3-N,50%,30%,20% for SO 4-S. Dry depositions and canopy leaching in cypress throughfall showed lower values compared with cedar.