皆伐对杉木人工林土壤呼吸的影响

应用密闭室碱吸收法对杉木人工林皆伐后的土壤呼吸及各分室呼吸进行为期1年定位研究,结果表明,杉木林皆伐后前4个月土壤呼吸显著高于对照(未伐地)的,皆伐6个月后则显著低于对照的,但伐后1年内的平均土壤呼吸则与对照的无显著差异。皆伐地枯枝落叶层呼吸和矿质土壤呼吸分别在伐后的5个月和6个月内显著高于对照的,但此后则与对照的无显著差异。皆伐地根系呼吸除在伐后当月显著高于对照的外,第3个月迅速降低至消失。皆伐地土壤呼吸、枯枝落叶层呼吸和矿质土壤呼吸最大值出现时间均较对照的有所提前。伐后1年内皆伐地枯枝落叶层呼吸、矿质土壤呼吸和根系呼吸占土壤呼吸的比例分别为34·5%、63·9%和1·6%,而对照的则分别为23·4%、50·1%和26·5%。双因素关系模型拟合结果表明,土壤温度和土壤湿度共同解释皆伐和对照土壤呼吸速率变化的54%和90%。皆伐地土壤呼吸及各分室呼吸对土壤温度的敏感性低于对照的,但对土壤湿度的敏感性则高于对照的。皆伐地土壤呼吸、矿质土壤呼吸和枯枝落叶层呼吸的Q10分别为1·42、1·53和1·34,而对照的土壤呼吸、矿质土壤呼吸、枯枝落叶层呼吸和根系呼吸的Q10则分别为2·42、1·81、2·40和4·41。

EFFECT OF CLEAR-CUTTING ON SOIL RESPIRATION OF CHINESE FIR PLANTATION

Effect of clear-cutting on soil respiration was investigated in a Chinese fir (Cunninghamia lanceolata) plantation in Fujian Province for one year (from February 2003 to January 2004) following clear-cutting. Soil respiration was measured in situ utilizing the alkali sorption technique. During the first 4 months clear-cutting significantly increased soil respiration level, which dropped drastically in the following 6 months, while there was no significant difference in mean soil respiration rates during the study periods between the clear-cut site and the control site (intact site). Respiration rates of forest floor and mineral soils in the clear-cut site were significantly higher than in the control site during the first 5 and 6 months, and there were no significant differences thereafter. Root respiration rate in clear-cut site declined rapidly and disappeared after the 3 months, and was only significantly higher than in the control site during the first month. The contributions to total CO_2 evolution from forest floor respiration, mineral soil respiration and root respiration in clear-cutsite were 34. 5%, 63.9% and 1.6%, and were 23.4%, 50.1% and 26.5% in control site, respectively. Soil temperature and soil moisture together accounted for 54% and 90% of variations of the soil respirations in the clear-cut and the control sites. Soil respiration and its compartments in the clear-cut site were lower in temperature sensitivity but higher in moisture sensitivity than in the control site. Q_ 10 values for total soil respiration, mineral soil respiration, and forest floor respiration was 1.42, 1.53, and 1.34, respectively, in the cut site and 2.42, 1.81, and 2.40, respectively, in the control site. Root respiration of the control site was the highest in Q_ 10 value, being as high as 4.41.