江南油杉细根生物量空间分布及其对土壤水分的响应

【目的】探明广西不同栽培区江南油杉细根生物量的空间分布共性及其对土壤水分的响应机制。【方法】以广西3个栽培区江南油杉人工幼林为研究对象,采用根系全株分层挖掘和根系形态结构分析法,定量分析江南油杉幼树不同径级细根生物量密度、根长密度和表面积密度的空间分布特征。【结果】1)江南油杉幼林期细根生物量在垂直方向上主要分布在0~90 cm土层中,且0~60 cm范围内的细根生物量占总量的81.83%,细根生物量随土层深度的增加呈升高—降低—再升高的趋势。细根生物量在水平方向上主要分布在距树干0~100 cm范围内,其中0~50 cm细根生物量占总量的87.40%。综合不同径级根长密度和根表面积密度分析结果表明,d <5 mm径级细根是江南油杉幼树占主导地位的吸收根系,其中0.5 mm≤d <2 mm径级细根在不同样地以及不同土层中的根长密度值最大,是决定江南油杉幼树根长密度分布特征的主要根系。2)江南油杉细根总生物量、根系长度、根表面积与土壤水分含量呈显著的相关性,表明江南油杉细根分布对土壤水分含量的响应敏感。【结论】江南油杉细根生物量垂直分布的"双峰"特征有利于根系对表层土壤水分在下渗过程中的二次吸收利用。0~60 cm土层是江南油杉幼树根系发挥生理功能的主要土层,可作为该树种水肥管理的重要区域。

Spatial structure of fine root biomass and its response to soil moisture of Keteleeria cyclolepis Flous

【Objective】The commonality in the spatial distribution of fine root biomass of Keteleeria cyclolepis Flous and the mechanism for its response to soil moisture in different cultivation areas of Guangxi were investigated. 【Method】The plantations of young Keteleeria cyclolepis Flous in three cultivation areas of Guangxi were taken as the object, and whole-plant layered excavation and morphological structure analysis of the root system were adopted to quantitatively analyze the spatial distribution characteristics of fine root biomass density, root length density and surface area density of young Keteleeria cyclolepis Flous in different diameter classes. 【Result】1) Fine root biomass of young Keteleeria cyclolepis Flous was mainly distributed in the 0-90 cm soil layer in the vertical direction, with fine root biomass in the 0-60 cm soil layer occupying 81.83% of the total;fine root biomass increased, decreased, and then increased again with the increase of soil depth.Fine root biomass was mainly distributed at 0-100 cm from the trunk in the horizontal direction, among which fine root biomass at 0-50 cm was 87.40% of the total. Based on the analysis of root length density and root surface area density in different diameter classes, fine root with diameter d < 5 mm was the dominant absorbing root system of young Keteleeria cyclolepis Flous;fine root with 0.5 mm ≤ d < 2 mm showed the highest root length density in different sample cultivation areas and in different soil layers, which was the main root system determining the distribution characteristics of the root length density of young Keteleeria cyclolepis Flous. 2) Soil moisture content was also significantly correlated with total fine root biomass, root length, and root surface area of Keteleeria cyclolepis Flous respectively, indicating that fine root distribution of Keteleeria cyclolepis Flous was sensitive to soil moisture content.【Conclusions】The double-peak vertical distribution of fine root biomass of Keteleeria cyclolepis Flous conducive to the secondary absorption and utilization of surface soil moisture. The 0-60 cm soil layer is the primary place for exerting the physiological function of the root system of young Keteleeria cyclolepis Flous and can thus serve as an important area for water and fertilizer management of this tree species.