岩溶峡谷区不同退耕还林地土壤有机碳库差异分析

Difference analysis of soil organic carbon pool in different forestlands returned from farmlands in karst gorge area

为揭示岩溶区不同退耕还林地对土壤有机碳库及碳库管理水平的影响,探讨花江峡谷地区耕地和5种典型退耕还林（草）地（撂荒、车桑子、花椒、椿树和油桐）土壤剖面有机碳质量分数、密度以及碳库管理指数的变化情况.结果表明：1）与耕地相比,退耕还林明显提高了有机碳质量分数和密度（P＜0.05）,0 ～ 20 cm土层总有机碳质量分数为13.00 ～ 34.07 g/kg,其中耕地最低,椿树林地最大;土壤剖面中有机碳密度大小表现为椿树林＞油桐林＞撂荒地＞车桑子地＞花椒地＞耕地.2）6种样地土壤有机碳质量分数和密度均随土层深度的增加而降低,O ～ 20cm土层总有机碳质量分数分别是剖面均值的1.11 ～1.37倍,0～ 20 cm土层有机碳密度占整个剖面的35.68％～46.45％,显著高于其他各层,具有明显的表聚性.3）以耕地为参照,除花椒地外,其他4种退耕还林地碳库管理指数均明显大于1,即退耕能有效提高土壤碳库管理水平,且以椿树和油桐林地效果最佳.此外,土壤活性有机碳比率的变化与总有机碳质量分数的变化一致,土壤活性有机碳比率可以作为反映土壤碳库管理水平的重要指标.退耕具有提升土壤碳库及其质量的潜力,该区在生态恢复中要注意选择合适的退耕模式,增加植被盖度、减少人为扰动.

To determine the effects of different forestlands returned from farmlands on soil organic carbon and carbon pool management level in karst areas,soil organic carbon （SOC） contents,density and carbon management index （lCM）under six different land-use types,including conventional farmland （CT）,abandoned farmland （AF）,farmland returned to plantations of Dodonaea viscosa （DV）,Zanthoxylum scandens （ZA）,Toona sinensis （TS） and Vernicia fordii （VF）,were studied in Huajiang gorge area of Guizhou Province.The results showed that：1） compared with farmland,total organic carbon （TOC） content and density of lands converted from farmlands increased significantly （P ＜ 0.05）.TOC in 0-20 cm layer ranged from 13.00-34.07 g/kg,with farmland the lowest while Toona sinensis the highest.TOC density in soil profile presented a trend of TS ＞ VF ＞ AF ＞ DV ＞ ZA ＞ CT.2） Both TOC content and TOC density decreased with the increase of soil depth in all land-use types.TOC contents in 0-20 cm soil were 1.11-1.37 times as high as the cross-sectional mean value,while SOC density in 0-20 cm deep soil accounted for 35.68％-46.45％ of the entire section,showing an obvious table cohesion.3） Taking farmland as a reference,IcM of all the other four converted lands were obviously greater than 1 except for Z.scandens.Vegetation recovery can effectively improve soil carbon pool management level,with T.sinensis and V.fordii having the highest efficiency.In addition,the change of LOC/TOC ratio had the same tendency as the variation of TOC content.RL/T can be used as an important indicator to reflect the level of carbon management.In summary,returning farmland to forests has the potential of expanding capacity of carbon pool and improving soil quality; therefore,we should pay attention to selecting suitable restoration modes,increasing vegetation cover as well as reducing human disturbance.