林下植被抚育对樟树人工林土壤活性有机碳库的影响

Effects of understory removal on soil labile organic carbon pool in a Cinnamomum camphora plantation

以我国亚热带东部地区48年生樟树人工林为对象，并以未抚育林分为对照，分析了不同林下植被处理对两种林分0—60cm土层土壤活性有机碳含量及其比率的影响．结果表明：与对照相比，抚育林分土壤总有机碳和易氧化碳含量均下降，且在0～10和10～20cm土层之间的差异达到显著水平；而水溶性有机碳（0～10和10～20cm土层除外）和轻组有机质含量升高，但差异不显著．抚育林分土壤水溶性有机碳占总有机碳的比率高于对照，而易氧化碳占总有机碳的比率则相反．两种林分土壤中水溶性有机碳、易氧化碳、轻组有机质与总有机碳含量均呈显著或极显著相关，其中，抚育林分的易氧化碳和轻组有机质与总有机碳的相关系数大于对照，而水溶性有机碳与总有机碳则相反．两种林分中，易氧化碳、轻组有机质、总有机碳与土壤养分的相关性均达到显著或极显著水平，而抚育林分土壤水溶性有机碳与水解氮、速效磷、交换性钙和交换性镁的相关性不显著．

Taking a 48-year-old Cinnamomum camphora plantation in the eastern area of our sub- tropics as test object, this paper studied the labile organic carbon contents and their ratios to the total organic carbon （TOC） in 0-60 cm soil layer under effects of understory removal （UR）. As compared with no understory removal （CK） , the soil TOC and easily-oxidized carbon （EOC） con- tents under UR decreased, with a decrement of 4.8% -34.1% and 27.1% -36.2% , respectively, and the TOC and EOC contents had a significant difference in 0-10 cm and 0-20 cm layers, respectively. The water-soluble organic carbon （WSOC） （except in 0-10 cm and 10-20 em la- yers） and light fraction organic matter （LFOM） under UR increaesd, but the difference was not significant. The ratio of soil WSOC to soil TOC in UR stand was higher than that in CK stand, while the ratio of soil EOC to soil TOC showed an opposite trend. In the two stands, soil WSOC, EOC, and LFOM had significant or extremely significant correlations with soil TOC, and the correlation coefficients of soil EOC and LFOM with soil TOC were higher in UR stand than in CK, but the correlation coefficient between soil WSOC and TOC was in opposite. The soil EOC, LFOM, and TOC in the two stands were significantly or extremely significantly correlated with soil nutrients, but the soil WSOC in UR stand had no significant correlations with soil hydrolyzable N, available P, ex- changeable Ca, and exchangeable Mg.