基于组内-组间主成分分析的土地利用与团聚体有机碳关系的研究

通过对喀斯特山区典型土地利用方式下(灌丛、水田、菜园、玉米地和退耕地)土壤有机碳、团聚体有机碳在不同土壤层次下(0~10、10~20、20~30 cm)含量的系统研究,结合组内-组间主成分分析方法,探讨了喀斯特山区土地利用与团聚体有机碳分布的关系.结果表明:不同土地利用方式下土壤团聚体组成均以大粒径团聚体为主,并且 > 2 mm粒径团聚体对土壤总有机碳的贡献率可高达70%以上.随土壤层次的增加,土壤有机碳和团聚体有机碳含量降低明显,变幅范围分别为15.1~38.0 和15.4~40.3 g· kg^-1,表现以水田含量最高,菜园和灌丛相对居中,而以退耕3 a 草丛最低.组内-组间主成分分析结果显示,不同土地利用方式下土壤有机碳和团聚体有机碳的累积效应按水田、菜园、灌丛、退耕15 a 草丛、玉米地和退耕3 a 草丛依次下降,表明水田可作为喀斯特山区土壤有机碳固定的优势农业类型.与玉米地相比,退耕3 a 草丛有机碳储量降低了15.8%,而退耕15 a 草丛土壤有机碳储量有所提高,但恢复速率相对缓慢,以每年0.35 Mg· hm^-2的速度增加.

The Study of Relationship Between Land Use and Aggregate- Associated SOC Based on Between-Within Classes PCA in the Karst Region

Soil organic carbon (SOC) is the main medium for carbon migration in karst terrestrial ecosystems, understanding the change of SOC in different land use patterns will help us find out the carbon sequestration potential in karst area. In our study, SOC and aggregate-associated SOC were explored under five typical land use patterns (shrub land, vegetable land, paddy field, corn field, and abandoned land) at the 0-10, 10-20 and 20-30 cm depth, respectively, in Karst mountain area. We also discussed the relationship between land use and aggregate-associated SOC based on between-within classes PCA in the study area. Results showed that marcosized aggregate was the dominant fraction in soils under different land use patterns, and the contribution rate of > 2 mm aggregate was more than 70% to the total soil mass. The concentrations of SOC and aggregate associated- SOC sharply decreased with depth, which ranged from 15.1- 38.0 and 15.4-40.3 g· kg^-1, respectively. The highest SOC concentrations in whole soil and different aggregate fractions were basically found in paddy soil, followed by shrub and vegetable land, and were the lowest in grassland abandoned for three year. The between- within classes PCA result showed that, the cumulative effects of SOC, and aggregated associated-SOC under different land use patterns decreased following the order of paddy field, vegetable land, shrub land, grassland abandoned for 15 year, corn field, and grassland abandoned for three year. This suggests that paddy can be treated as an important land use pattern for long-term SOC sequestration in karst region of southwestern China. Compared to corn field, the SOC pool decreased by 15.8% in grassland abandoned for three year, while increased slightly in grassland abandoned for 15 years, and with a recovery rate of 0.35 Mg· hm^-2· a^-1.