不同造林密度马尾松人工林的根系生物量

摘要

采用全根挖掘法和土钻法,分别测定5种造林密度20年生马尾松林分平均标准木的单木和行间根系生物量,结果表明:平均标准木单木根系总生物量随林分密度的增大而减少,不同级别根系生物量的排序为根桩>粗根>大根>中根>小根,其中根桩和粗根占根系生物量构成的90%以上.行间不同径级根系生物量的排序为中根>细根>小根.不同密度对中根、小根和细根生物量呈现出随密度增加而逐渐变小的趋势.5种密度马尾松林分的根系主要分布在0～30 cm的表层土壤中,占根系总生物量的82%以上.随着土层深度的增加,不同密度林分行间根系生物量逐渐减少.数学模型拟合的结果表明,平均标准木单木各级根系生物量与林分平均胸径、平均树高及密度有较强的相关性,除了小根以外,相关系数均达到0.8以上,林分行间各级根系生物量与林分密度也表现出较好的相关性.%Root biomasses, of average individual tree, and in rhizosphere between rows in 20-year-old Pinus massoniana forests with five different planting densities were measured by total root excavating and soil auger methods. The results showed that total root biomass of the average individual tree decreased with increasing planting density. Biomasses of different root diameter classes ranked as root stake ＞ thick-root ＞ large-root ＞ medium-root ＞ small-root, among which root stake and thick-root accounted for more 90％ of total root biomass. Root Biomass of different diameter classes in rhizosphere between rows ranked as medium-root ＞ fine-root ＞ small-root. The effect of planting density on biomass decreased gradually from medium-root, small-root to fine-root. Under the five planting densities, major roots distributed in 0-30 cm upper soil, accounted for more than 82％ of total root biomass. Root biomass in rhizosphere between rows decreased with increased soil depth in all planting densities. Mathematic models showed that root biomasses of different classes of average individual tree were correlated to stand average breast diameter, average height and planting density.The correlation coefficients were all above 0.8 except for small-root. The root biomass of different classes in rhizosphere between rows was also correlated to planting density.