缙云山土地利用方式对土壤活性有机质及其碳库管理指数的影响

Effects of the Different Land Use on Soil Labile Organic Matter and Carbon Management Index in Junyun Mountain

通过选取缙云山向阳坡同一海拔高度处的亚热带常绿阔叶林（简称林地）、坡耕地、果园和撂荒地,测定分析0~60 cm深度土壤样品有机质及3种活性有机质组分含量,从而揭示了西南地区缙云山不同土地利用方式对土壤有机质、3种活性有机质及其有效率（ER）以及碳库管理指数（CMI）的影响.结果表明,4种土地利用方式下,土壤有机质、活性有机质含量以及ER和CMI均随土壤深度的增加而降低,其中土壤有机质、活性有机质及其CMI的剖面分布趋势相似,林地土壤有机质、活性有机质及其CMI主要富集在0~10 cm土层,果园主要富集在0~20 cm土层,而坡耕地和撂荒地从上而下的降低则比较均匀.在0~60 cm土壤深度内的土壤有机质以及3种活性有机质平均含量均为撂荒地〉林地〉果园〉坡耕地,将林地转变为果园和坡耕地后,有机质含量分别降低了21.56%（P〉0.05）和55.90%（P〈0.05）,将坡耕地闲置撂荒后,有机质、低、中、高活性有机质含量分别升高了238.86%（P〈0.05）、144.2%（P〈0.05）、153.3%（P〈0.05）和242.7%（P〈0.05）.方差分析发现3种土壤ER在不同土地利用方式之间并无明显差异,表明土壤ER对土地利用变化并不敏感.不同土地利用方式下3种活性有机质CMI均为撂荒地最高,林地次之,果园和坡耕地最低,表明林地开垦导致土壤碳截存降低,土壤向着质量退化的方向发展,而坡耕地撂荒则增强了土壤的碳汇功能,土壤质量向着良性方向发展.3种活性有机质与全氮、速效磷和速效钾呈极显著正相关关系,与土壤容重呈极显著负相关关系,表明活性有机质与土壤理化性质关系密切,是反映土壤养分和衡量土壤质量的重要指标.

The impacts of different land use on soil organic matter （SOM） , soil labile organic matter （SLOM） and their efficiency ratios （ER）, and soil carbon management index （CMI） were studied in this study. Subtropical evergreen broad-leaved forest （abbreviation： forest） , sloping farmland, orchard and abandoned land were selected and soils at the depths of 0-10, 10-20, 20-30, 30-40, 40-50 and 50-60 cm were sampled in the spring of 2011 to determine the contents of soil organic matter and labile organic matter. The results showed that the contents of soil organic matter and soil labile organic matter both decreased with the increase of soil depth under all four land use types; however, forest and orchard enriched SOM and SLOM contents in the 0-10 cm and 0-20 cm soil layers, respectively, while the contents of SOM and SLOM decreased evenly in sloping farmland and abandoned land. In the whole soil layer （0-60 cm） , the order of SOM and SLOM contents was abandoned land 〉 forest 〉 orchard 〉 sloping farmland, indicating that at the conversion from forest into orchard or sloping farmland, SOM was reduced by 21.56% （P 〉 0.05） and 55.90% （P 〈 0.05） , respectively, and at the conversion from sloping farmland into abandoned land, the low SLOM, middle SLOM and high SLOM increased by 144.2% （P〈0.05）, 153.3% （P〈0.05） and 242.7% （P 〈0.05）, respectively. There was no significant difference in low ER, middle ER and high ER among the four land uses as suggested by ANOVA which showed that SRs were not sensible to the change of land use. All three CMIs were in the order of abandoned land 〉 forest 〉 orchard 〉 sloping farmland, revealing that forest reclamation resulted in the reduction of soil organic carbon storage and the decline of soil quality, and the abandonment of sloping farmland would increase soil carbon sink and improve soil quality. Three kinds of SLOM were all positively correlated with soil total nitrogen, available phosphorus and available potassium, while negatively correlated with soil density bulk, indicating that SLOM had close relationships with soil physical and chemical characters and could be used as an important index to reflect soil nutrient status and judge soil quality.