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于缙云山阳坡同一海拔高度处选择了亚热带常绿阔叶林(简称林地)、荒地、坡耕地和果园4种土地利用方式,在0~60 cm的土壤深度内每隔10 cm采集一个土壤样品,测定大团聚体(>2 mm)、中间团聚体(0.25~2 mm)、微团聚体(0.053~0.25 mm)以及粉+黏团聚体(<0.053 mm)这4种粒径团聚体内的土壤活性有机碳(labile organic carbon,LOC)的含量,分析缙云山不同土地利用方式对团聚体LOC的影响.结果表明,各粒径团聚体中LOC含量均随土壤深度的增加而显著降低,呈现出明显的垂直递减性;在0~60 cm土壤深度的各土层上,基本上均表现为林地和撂荒地各粒径团聚体中LOC含量高于坡耕地和果园.采用土壤等质量方法计算LOC储量,显示大团聚体LOC储量为林地(3.68 Mg·hm-2)>撂荒地(1.73 Mg·hm-2)>果园(1.43 Mg·hm-2)>坡耕地(0.54 Mg·hm-2);中间和微团聚体LOC储量为撂荒地(7.77 Mg·hm-2和5.01 Mg·hm-2)>林地(4.96 Mg·hm-2和2.71 Mg·hm-2)>果园(3.55 Mg·hm-2和2.10 Mg·hm-2)>坡耕地(1.68 Mg·hm-2和1.35 Mg·hm-2);粉+黏团聚体LOC储量为撂荒地(4.32 Mg·hm-2)>果园(4.00 Mg·hm-2)>林地(3.22 Mg·hm-2)>坡耕地(2.37Mg·hm-2).除粉+黏团聚体LOC储量略低于果园外,林地和撂荒地其他粒径团聚体LOC储量均高于果园和坡耕地,表明林地开垦为果园和坡耕地会导致LOC的降低,而坡耕地撂荒则会促进LOC的增加.林地和荒地LOC主要分布在中间团聚体,而果园和坡耕地则为粉+黏团聚体内LOC储量最高,表明在土地利用的转变过程中,粒径较大的团聚体更容易积累或损失LOC.4种土地方式下各粒径团聚体中LOC分配比例随土壤深度的增加而降低,果园和坡耕地各粒径团聚体内LOC分配比例略高于林地和撂荒地,表明林地和撂荒地土壤有机碳(soil organic carbon,SOC)性质更稳定,更有利于碳在土壤中的留存,从而减少SOC矿化分解向大气的释放.相关分析表明,土壤团聚体LOC含量与土壤团聚体总有机碳含量呈极显著正相关关系,表明团聚体LOC可以作为衡量西南地区山地土壤团聚体有机碳动态的一个敏感性指标.
At the same altitude of Jinyun Mountain, four land use patterns of subtropical evergreen broad-leaved forest (forestland), wasteland, sloping farmland and orchard were selected, and one soil sample was collected every 10 cm in soil depth of 0-60 cm The soil contents of four aggregates (> 2 mm), middle aggregates (0.25-2 mm), microaggregates (0.053-0.25 mm), and powder + aggregates (<0.053 mm) The content of LOC (LOC) in the soil aggregates and the effect of different land use types on the LOC of aggregates in Jinyun Mountain were analyzed.The results showed that the content of LOC in each size aggregates decreased significantly with the increase of soil depth, Of the total soil depth at 0-60 cm soil depth, the content of LOC in the aggregates of woodland and abandoned wasteland was higher than that of sloping farmland and orchard, soil mass method was used to calculate the LOC reserves , And showed that the LOC of large aggregates was 3.68 Mg · hm -2> abandoned farmland 1.73 Mg · hm -2> 1.43 Mg · hm -2 or 0.54 Mg · hm -2 farmland. The total amount of LOC in middle and microaggregates ranged from 7.77 Mg · hm-2 and 5.01 Mg · hm-2 to 4.96 Mg · hm -2 and 2.71 Mg · hm -2 in forested land, (> 3.55 Mg · hm-2 and 2.10 Mg · hm-2) in sloping fields (1.68 Mg · hm-2 and 1.35 Mg · hm-2), respectively; hm-2> 4.00 Mg · hm-2 or 3.22 Mg · hm-2 in forestland or 2.37Mg · hm-2 in sloping farmland, The LOC reserves of other aggregates of aggregates in forestland and abandoned land were higher than those in orchard and sloping farmland, indicating that the land reclamation of orchard and sloping farmland would lead to the decrease of LOC, while the sloping land fallow would promote the increase of LOC. In the middle of aggregates, while in orchards and sloping fields, the highest amount of LOC in powder and sticky aggregates indicates that agglomerates with larger particle size are more likely to accumulate or lose during land use conversion The distribution ratio of LOC in particle size aggregates decreased with the increase of soil depth, and the LOC allocation proportion in each particle size aggregate in orchard and slope farmland was slightly higher than that in forestland and fallow land, indicating that soil organic carbon (SOC ) Is more stable in nature and more conducive to carbon retention in the soil, thereby reducing the release of SOC mineralization decomposition to the atmosphere.Relationship analysis showed that soil aggregates L There was a significant positive correlation between OC content and total organic carbon in soil aggregates, indicating that LOC could be used as a sensitive index to measure organic carbon in mountainous soil aggregates in southwestern China.