粗枝云杉不同径级根系分解过程中4种养分元素的释放特征

植物根系分解是养分元素进入土壤的重要途径之一.为了解径级对根系分解过程中养分元素释放的潜在影响,以川西亚高山针叶林中的粗枝云杉(Picea asperata)为对象,采用原位分解试验,研究云杉3个径级(0-2 mm,2-5 mm和5-10 mm)根系分解过程中钾(K)、钠(Na)、钙(Ca)和镁(Mg)元素的浓度、残留率和释放率动态特征.结果表明:4种元素在冬季和生长季节释放模式不同,除Na和Ca外,其他两种元素冬季的释放率大于生长季;径级对根系元素浓度和残留率有显著影响,随着径级的增大,元素浓度通常会降低,元素残留率则有增加的趋势,K和Ca尤为明显;分解两年后,K、Na、Ca和Mg分别释放了84%-87%、62%-70%、2%-26%和34%-56%.综上所述,径级显著影响川西亚高山粗枝云杉根系养分元素的释放特征,径级效应与元素种类和季节动态有关联.(图3表1参51)

The release dynamic of four nutrient elements in decomposing Picea asperata roots of different diameters

Root decomposition is a crucial channel for nutrient entry into soils. In order to explore the potential effect of diameter on the release pattern of nutrient elements, a common species in western Sichuan, Picea asperata, was chosen in this study. An in-situ decomposition experiment was conducted to investigate K, Na, Ca, and Mg concentrations, remaining percentage, and release rate of three root diameter classes(0-2, 2-5, and 5-10 mm). The release pattern of the four elements differed between winter and the growing season. The release rates of K and Mg were greater in the winter than in the growing season, but the opposite was true for Na release. Root diameter significantly affected the element concentration and remaining percentage. The element concentration generally declined, but the remaining percentage tended to increase with increasing root diameter, especially K and Ca. In addition, K, Na, Ca, and Mg released 84%-87%, 62%-70%, 2%-26%, and 34%-56%, respectively, by the end of decomposition. In conclusion, root diameter has a significant effect on nutrient release in P. asperata roots and this effect depends on the element category and seasonal period.