不同生长年限紫花苜蓿草地土壤团聚体有机碳分布特征

Distribution characteristics of organic carbon fraction in soil aggregates of grassland with different alfalfa growing ages

对黄土高原地区不同生长年限紫花苜蓿(Medicago sativa L.)草地土壤团聚体0~40 cm土层的分布及其有机碳含量特征进行研究。结果表明:土壤总有机碳随着生长年限的增加而呈先增加后减小的趋势,各年限0~10 cm土壤有机碳含量均最高,呈表聚现象。不同生长年限紫花苜蓿湿筛处理下土壤团聚体均以<0.106 mm粒级团聚体为主,约为40%~90%,随土层深度增加而减小;>0.25 mm粒级团聚体在4年时含量最高,并随生长年限的增加呈先增加后减小的趋势。不同年限紫花苜蓿土壤团聚体有机碳以<0.106 mm粒级团聚体含量最高,随粒级的减小而增加;不同年限紫花苜蓿土壤20~40 cm团聚体有机碳含量高于0~20 cm土层,并随生长年限增加呈先增加后减小的趋势。

The distribution of organic carbon fractions in soil aggregates in soil layer of 0 - 40 cm was studied under alfalfa（ Medicago sativa L.） plantation of different ages. The result showed that soil organic carbon firstly increased and then decreased with the increase of alfalfa planting years,and it was the highest at 0 - 10 cm soil depth for all years,showing a phenomenon of surface accumulation. The soil granule structure of alfalfa plantation was dominated by 〈0. 106 mm aggregation which approximately accounted for 40% - 90% of all aggregates,and decreased with the soil depth; 〉0. 25 mm aggregation was the highest at 4 years,which was firstly increased with planting years then decreased. The distribution of soil organic carbon in soil aggregates was mainly found in 〈0. 106 mm fraction of aggregates in the soil,and increased with the decreasing of particle size. The distribution of organic carbon in soil aggregates at 20 - 40 cm depth was higher than 0 - 20 cm depth,and increased with planting years then decreased.