杉木观光木混交林和杉木纯林群落细根生产力、分布及养分归还

研究了福建三明27a生杉机光木混交林和杉木群落细根（d＜2mm）的生产力、分布、和养分归还。结果表明，混交林细根生物量、N、P养分现存量分别为5．381thm^2、48．085kghm^-2和4．174kghm^-2，分别比杉木纯林增加17．4％、27．2％和20．0％，混交林林细根的年净生产力达4．124thm^-2a^-1，比纯林高出16．9％，混交林杉木和观光木细根均在表层土壤富集，而在较深层土壤再会得分布具镶嵌性；与混交林杉林相比，纯林杉木土吉表层细根量较少，最大分布层次下移，混交林中观光木细根的周转速率咪1．16，杉木为0．96和0．95；而林下植被层细根周转速率（1．46－1．52）均同于相应的乔木层，混交林细根的年死亡量、N和P养分年归还量分别达2．119thm^-2、18．559kghm^-21．565kgkhm^-2，分别是纯林的1．21倍、1．23倍和1．14 倍，其中林下植被细根占有较为重要位置，对细根分布与土壤性质的相关分析表明，细根的垂直分布与土壤全N的相关性最强（0．87－0．89）。

PRODUCTION, DISTRIBUTION AND NUTRIENT RETURN OF FINE ROOTS IN A MIXED AND A PURE FOREST IN SUBTROPICAL CHINA

The studies on production, distribution and nutrient return of fine roots ( d <2 mm) in a mixed Chinese fir ( Cunninghamia lanceolata ) Tsoong' tree ( Tsoongiodendron odorum ) forest and a pure Chinese fir forest at age 27 were carried out in Sanming of Fujian, China. The standing crops of dry matter, N and P in fine roots of the mixed stand were 5.381 t hm -2 , 48.085 kg hm -2 and 4.174 kg hm -2 , 17.4 %, 27.2% and 20.0% higher than those of the pure stand, respectively. The fine root production in the mixed forest was up to 4.124 t hm -2 a -1 , 16.9% higher than that in the pure stand. Fine roots of Chinese fir and Tsoong' tree in the mixed forest both concentrated in the surface soil, and showed a vertical stratification in the subsoil. Compared with those in the mixed forest, fine roots of Chinese fir in the pure forest had a deeper rooting zone, with a lower root density in the superficial soil. The turnover rates of fine roots for Tsoong' tree and Chinese fir in the mixed stand, and Chinese fir in the pure stand, were 1.16, 0.96 and 0.95, respectively. The undergrowth species had higher root turnover rates than their respective tree layers (1.46 in the mixed forest and 1.52 in the pure stand). The annual mortality, annual return of N and P of fine roots in the mixed forest amounted to 2.119 t hm -2 , 18.559 kg hm -2 and 1.565 kg hm -2 , 1.21, 1.23 and 1.14 times as much as that in the pure forest respectively. Bulk density, moisture content, total N and humic C were strongly correlated with fine root density along the soil profile in the two forests, with total N giving the highest coefficients of determination. Fig 1, Tab 4, Ref 32