通过对福建三明27年生杉木观光木混交林（混交比例2׃1）及杉木纯林群落N、P养分循环进行为期2年的研究，结果表明，混交林中杉木和观光木地上各组分的N、P含量大小均为叶>活枝（或皮）>枯枝>干，而根系的则随径级的减小而增大，且观光木各组分的N 含量均高于杉木的；混交林群落的N、P总积累量达585.223kgּhm-2和128.784kgּhm-2，分别是纯林群落的1.5倍和1.3倍。混交林群落N、P养分年归还量达75.740和5.493kgּ hm-2，分别是杉木纯林的113.0%和79.6%。混交林通过凋落物、降水淋溶和细根枯死三种途径的N归还量分别占群落总归还量的67.1%、8.4%和24.5%，而纯林的则为分别为69.3%、8.1%和22.6%；混交林三种途径的P归还量分别占群落总归还量的64.0%、7.5%和28.5%；而纯林则为74.8%、5.3%和19.9%。混交林中林下植被层的N、P归还量分别占群落总归还量的14.8%和37.3%；而纯林的则为29.5%和59.4%。混交林群落的N、P富集率和利用系数均低于纯林的，而周转期则均大于纯林的。混交林群落的P吸收系数小于纯林的，而循环系数则高于纯林的，但其两者的N吸收系数和循环系数则相似。

森林土壤呼吸的近2/3是由林木根呼吸产生的，林木根呼吸对估计森林C 吸存及构建森林生态系统碳动态模型有重要意义，是全球碳循环研究的一个重要组成部分。林木根呼吸包括生长呼吸和维持呼吸，不同森林生态系统林木根呼吸对土壤呼吸的贡献大多在40%-60%范围内，林木根呼吸在生长季节较高而休眠季节较低。测定林木根呼吸的主要方法有排除根法、离体根法、同位素法和原位PVC 管气室法，前两者相对简单、成本低，常用于森林生态系统中；同位素法可原位测定根呼吸，对土壤干扰较小，但不易操作，且成本高。根呼吸受土壤温度、根直径大小、根组织N 浓度、环境CO2 浓度、土壤湿度、养分有效性等因素的影响。今后的研究应集中在以下方面：1）探讨和比较不同条件下测定根呼吸组成（生长呼吸、维持呼吸）的最合适方法；2）加大在野外条件下使用有效方法分离根呼吸和根际微生物呼吸的力度；3）对森林生态系统根呼吸动态进行长期的定位研究；4）进一步加强研究不同气候带，不同森林类型林木根呼吸，并将研究尺度从气室扩大到区域或全球水平；5）加强林木根呼吸对全球变化的响应及机制的研究；6）对林木根呼吸进行多学科合作研究将为全球C循环做出独特贡献。

ed in Yizhou work area of Yizhou state Forestry Centre in Fujian Province, China, were examined following slash burning to compare nutrient capital and topsoil properties with preburn levels. After fire, nutrient (N, P and K) removal from burning residues was estimated at 302.5 kg ha-1 in the CF and 644.8 kg ha-1 in the EB. Fire reduced the topsoil capitals of total N and P by ～20% and ～10%, respectively in both forests. While K capital was increased in the topsoils of both forests following fire. Total site nutrient loss through surface erosion was 28.4kg (N) ha-1, 8.4kg (P) ha-1 and 328.7kg (K) ha-1 in the CF. In the EB, the losses of total N, P and K were 58.5, 10.5 and 396.3kg ha-1, respectively. Improvement of soil structure and increase in mineralization of nutrients associated with increased microbe number and enzyme activities and elevated soil respiration occurred 5 days after fire. However, organic matter and available nutrient contents and most of other soil parameters declined one year after fire on the burned CF and EB topsoils. These results suggest that short-term site productivity can be stimulated immediately, but reduced subsequently by soil and water losses, especially in South China, where high-intensity precipitation, steep slopes and fragile soil factor can be expected. Therefore, the silvicultural measurements should be developed in plantation management.