土地利用对亚热带红壤低山区土壤有机碳和微生物碳的影响

 【目的】研究土地利用变化对土壤有机碳（SOC）和微生物量碳（SMBC）含量的影响。【方法】采用典型样区密集取样（水田和旱地3～4个样/ha、果园2～3个样/ha、林地0.2～0.5个样/ha）和野外调查，对亚热带红壤低山肯福样区的水田、旱地、果园和林地表层（0～20 cm）SOC和SMBC含量及其变化进行了研究。【结果】本区SOC、SMBC含量和微生物碳与有机碳比率（SMBC/SOC）分别为(17.53±5.02)g·kg-1，(278±174)mg·kg-1和(1.56±0.84)%。其中，林地SOC、SMBC含量和SMBC/SOC分别为(18.20±4.53)g·kg-1、(293±111)mg·kg-1和(1.58±0.39)%。水田SOC、SMBC含量和SMBC/SOC较林地依次提高了15.5%，84.0%和73.9%（P＜0.01）；与林地相比，旱地SOC含量（17.50±4.89）g·kg-1略有降低（P＞0.05），SMBC含量和SMBC/SOC分别减少29.1%和24.2%（P＜0.01）；果园SOC、SMBC含量和SMBC/SOC比林地分别降低了26.8%，46.1% 和26.1%（P＜0.01）。除水田外，其余土地利用方式的SOC与SMBC含量之间均存在极显著的相关关系。【结论】亚热带红壤低山生态景观单元内林地开垦为水田增加了SOC的积累和土壤微生物活性，林地开垦为旱地和果园不同程度地降低了SOC的积累和微生物活性。

Effects of Land Use on Soil Organic C and Microbial Biomass C in Hilly Red Soil Region in Subtropical China

【Objective】In order to assess the impacts of land use change on soil organic carbon (SOC) and soil microbial biomass carbon (SMBC), the contents of SOC and SMBC of surface soil samples (0-20 cm) were investigated. 【Method】The dense sampling (the density of sampling for paddy and dry land is 3-4 per ha, for orchard is 2-3 per ha and for woodland is 0.2-0.5 per ha) and the field surveys in Kenfu demonstration area of environmental immigrants of the northwest of Guangxi, a hilly landscape of red soil area of subtropical China were carried out. 【Result】The average contents of SOC, SMBC and the ratio of SMBC and SOC were respectively (17.53±5.02) g·kg-1, (278±174) mg·kg-1 and (1.56±0.84)% in the area, respectively. The average contents of SOC, SMBC and the ratio of SMBC and SOC of the woodland were (17.53±5.02) g·kg-1, (278±174) mg·kg-1 and (1.58±0.39)%, respectively. Compared with the woodland, the contents of SOC and SMBC and the ratio of SMBC and SOC of the paddy field increased by 15.5%, 84.0% and 73.9% (P<0.01); The content of SOC of the dry land (17.50±4.89 g·kg-1) decreased slightly (P>0.05) compared with the woodland, that of SMBC and SMBC/SOC decreased by 29.1% and 24.2% (P<0.01); The content of SOC, SMBC and SMBC/SOC of the orchard decreased by 26.8%, 46.1% and 26.1% compared with the woodland (P<0.01). In addition, there were significant correlations between SOC and SMBC in different land use except the paddy field. 【Conclusion】This study indicated that the conversion of woodland into paddy field increased the accumulation of SOC and the microbial activity evidently in the hilly landscape of red soil area of subtropical China. However, the conversion of woodland into dry land or orchard reduced the content of SOC and the microbial activity to different degrees.