杉木观光木混交林细根的分布

对27年生混交比例为2行杉木和1行观光木的混交林和杉木纯林群落细根分布的研究表明，杉木和观光行间的杉木细根密度虽比极木行间的低8．5％，但观光木细根密度则高152．09％，其细根总密度比杉木与杉木行间的大10．43％。混交林中杉木各径级活动根密度呈单峰型分布，均以5－10cm土层最大，而观光木各径级各活细根主要分布在0－10cm土层内。纯林杉木各径活细根密度亦基本呈单峰型分布，但峰值出现在10－20cm或20－30cm土层。不同树种不同径级死细根的分布均与其各自的活细根分布相似。混交林中灌木细根密度在30－40cm的土层最大，而纯林中的灌木细根集中于0－10cm的表土层；混交林和纯林中的草木细根均集中在0－5cm土层。与纯林的相比，混交林中杉木细根主要分布的土层明显上移，表层土壤细根所占比重增大，有利于更好利用土壤养分和提高群落生产力。

Distribution of Fine Roots in a Mixed Cunninghamia lanceolata-Tsoongiodendron odorum Plantation

Fine roots were measured by soil core sampler in a mixed plantation of 27-year-old Cunninghamia lanceolata (C) and Tsoogiodeudron odorum (T) in Fujian Province. Fine root density of C at interrow between C and T was lower by 8.5% than that between C and C, but fine root denstiy of T and total fine root density were higher by 152.09% and 10.43%, respectively. High density of living fine roots with different thickness of C in mixed plantation appeared at 5-10 cm soil depth, whereas that of T at 0-10 cm. Compared to mixed plantation, living fine root density in pure C plantation appeared at 10 -30 cm of soil depth. The distribution of dead fine roots had the same pattern. In mixed plantation, upward trend of soil layer with maximum fine roots of C was obvious, showing that mixed plantation had an advantage over pure plantation in nutrient absorption.