喀斯特石漠化过程对土壤活性有机碳的影响

以贵州省花江峡谷区典型喀斯特石漠化小流域为研究区域,对潜在、轻度、中度、强度石漠化等级样地代表性土壤活性有机碳进行了测试分析.分析结果表明,随着石漠化程度的增加,土壤微生物生物量碳(sMBc)、轻组有机碳(LFOC)、可矿化碳(MC)、微生物商(qSMBC)呈下降趋势,微生物呼吸商(qCO2)呈上升趋势,与石漠化过程有一致性,能较好体现石漠化过程中土壤退化的本质.开垦序列土壤活性有机碳库的周转速率和土壤微生物碳库的下降速率大于樵采序列,使得开垦序列土壤即使在高的生物归还量下,形成土壤有机碳的比例相对较小.土壤SMBC,LFOC,MC,易氧化有机碳(LOC),qSMBC,qCO2等生物学性质除了与人为干扰方式有关外,还与植被生物量有关,可以体现土壤质量发展的方向,是石漠化过程土壤退化及恢复评价的敏感指标.

Effects of Active Soil Organic Carbon on the Processes of Karst Rocky Desertification

The research area is a typical karst catchment subject to rocky desertification in Huajiang Gorge,Guizhou Province.One representative soil sample was collected in each plot of strong,medium,slight,or latent desertification grade.The research focused on active soil organic carbon(ASOC) in the processes of rocky desertification.Results elucidated that the characteristics such as soil microbial biomass carbon(SMBC),light fraction organic carbon(LFOC),mineralizable carbon(MC),and microbial quotient(qSMBC) had a decreasing trend,while microbial metabolic quotient(qCO₂) had an increasing trend,which acted in accord with the direction of rocky desertification.The above biological characteristics could embody the essence of soil degradation in the processes of rocky desertification.The turn over speed of active SOC in reclamation sequence was higher than that in wood chopping sequence,while the decreased speed of SMBC in reclamation sequence was faster than that in wood chopping sequence.With the long period of accumulation,the wood chopping sequence kept higher SOC content than the reclamation sequence even with high amount of biological return.The biological characteristics such as SMBC,LFOC,MC,labile organic carbon(LOC),qSMBC,and qCO₂ were influenced both by anthropogenic disturbing ways and by the vegetation productivity and could embody the development direction of soil quality.Meanwhile,they were sensitive indexes of estimating soil quality degradation and restoration in the processes of karst rocky desertification.