格氏栲天然林与人工林土壤异养呼吸特性及动态

通过用静态碱吸收法对中亚热带福建三明格氏栲自然保护区内的格氏栲天然林和33年生的格氏栲人工林及杉木人工林的土壤异养呼吸进行为期2年的定位研究。结果表明，三种森林枯枝落叶层呼吸和无根土壤呼吸速率季节变化均呈单峰曲线，最大峰值出现在5月至6月，最小值出现在12月至1月。格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层呼吸速率平均值分别为CO2 79．88、44．37和21．02mgm^-2h^-1，无根土壤呼吸速率平均值分别为CO2 217．4、85．85和94．04mg m^-2h^-1。2002年枯枝落叶层呼吸速率和无根土壤呼吸速率主要受土壤温度影响，但在极端干旱的2003年则主要受土壤湿度的影响。双因素关系模型（R=ae^bTW^c）拟合结果优于仅考虑土壤温度或土壤湿度的单因素关系模型，土壤温度和土壤湿度共同解释不同年份枯枝落叶层呼吸和无根土壤呼吸速率季节变化的82％～85％和85％～92％。不同森林枯枝落叶层呼吸对土壤温度和湿度的敏感性均高于无根土壤呼吸的。格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层呼吸年通量分别为C3．76、2．63和1．23t hm^-2a^-1，无根土壤呼吸年通量则分别为C3．44、2．79和1．49t hm^-2a^-1。不同森林土壤异养呼吸通量的差异主要与枯落物数量和质量、土壤有机质数量和质量的差异有关。杉木林枯枝落叶层呼吸对干旱敏感性高于格氏栲（天然林和人工林）的，而人工林（杉木和格氏栲）的土壤有机C对干旱敏感性则要高于格氏栲天然林。

SOIL HETEROTROPHIC RESPIRATION IN NATIVE CASTANOPSIS KAWAKAMII FOREST AND MONOCULTURE CASTANOPSIS KAWAKAMII PLANTATIONS IN SUBTROPICAL CHINA

Soil heterotrophic respiration(HR)was investigated in one tract of native Castanopsis kawakamii forest(NF), a 33-year-old Castanopsis kawakamii plantation(CK)and a Cunninghamia lanceolata(Chinese fir,CF)plantation of the same age in Sanming,Fujian Province,China.Soil CO₂ efflux was measured in situ in a 2-year period with the alkali sorption technique.Respirations of root-free soils(R_RF)and litter layer(RL)were measured separately by trenching and removing litter, respectively.Both R_RF and R_L in the three forests showed a similar seasonal pattern with o ne single peak occurring during May or June and a valley during December or January.R_L averaged CO₂ 79188,44137 and 21102 mg m^-2 h^-1,and R_RF averaged CO₂ 21714,85185 and 94104 mg m^-2 h^-1 in NF,CK and CF,respectively.The model R=ae^bTW^c (R stands for soil CO₂ efflux, T for soil temperature and W for soil water content at 0~10 cm soil depth,and a,b,c for the constants)indicated that soil temperature and soil water content together could explain 82%~85% and 85%~92% of R_L and R_RF,respectively,with soil temperature being the dominating factor affecting soil respiration rate in 2002 and soil humidity in a dry year of 2003.R_L was more sensitive to variation in soil temperature and humidity than R_RF.Annual R_L averaged C 3176,2163 and 1123 t hm^-2 a^-1, and annual R_RF averaged C 3144,2179 and 1149 t hm^-2 a^-1,respectively,in the NF,CK,and CF.Differences in soil heterotrophic respiration between forests were associated with differences in quantity and quality of organic inputs,biomass and activity of roots,and content and components of soil organic carbon.R_L in CF showed higher sensitivity to drought than in CK and NF,and the sensitivity of soil organic C to drought was higher in the plantations(CK and CF)than in the native forest (NF).