黄土丘陵沟壑区不同种植年限紫花苜蓿草地土壤团聚体及其有机碳分布特征

Distribution characteristics of soil aggregates and itsorganic carbon of alfalfa grassland with differentgrowth years in Loess Hilly-gully region

摘要:

为了探索紫花苜蓿对土壤质量的影响,选取了黄土高原丘陵沟壑区3、7、12和18 a生紫花苜蓿草地0~40 cm土壤为研究对象,以农田土壤为对照(CK),采用干筛法研究了不同种植年限苜蓿草地土壤团聚体及其有机碳分布特征。结果表明:1)不同种植年限苜蓿草地土壤以＞5 mm的大团聚体为优势级别,占41.5%,而2~1 mm粒径团聚体含量最少,均＜10%。随种植年限的延长,大团聚体含量(R_0.25)和平均重量直径(MWD)均逐渐增加,至12 a达到最大,并与其它各年限达到显著性差异。2)各粒级土壤团聚体有机碳含量的变化趋势均为12 a＞18 a＞7 a＞3 a＞CK,1~0.25 mm粒级团聚体有机碳含量较高。3)土壤团聚体对有机碳的贡献率约有40%来自＞5 mm 粒级团聚体。＞5 mm 粒级团聚体有机碳储量随苜蓿种植年限延长呈增加趋势。不同种植年限0~20 cm 土层各粒级团聚体有机碳储量均高于20~40 cm 土层。研究结果在一定程度上揭示了不同年限人工苜蓿草地土壤团聚体及其有机碳分布特征,可为改善区域土壤质量及协调区域土地利用提供理论指导。

Abstract:

To explore the effects of alfalfa planting on soil quality,in this study, the 0~40 cm soil of 3-year (3 a),7-year (7 a),12-year (12 a),and 18-year (18 a) alfalfa grassland in Hilly and gully region of Loess Plateau was selected as the research object,and the farmland soil was used as the control (CK),we used dry-sieving method to study the soil aggregates and organic carbon distribution characteristics of alfalfa grassland in different planting years.The results showed that: 1) The greatest proportion of aggregates was observed at the size of＞5 mm in each alfalfa plantation years which approximately accounted for about 41.5% of all aggregates,and the least proportion was observed at the size of 2~1 mm which accounted for no less than 10.0%.With the extension of planting years,the proportion of large aggregates (R_0.25) and the average weight diameter (MWD) gradually increased, reaching the maximum at 12a,and the difference was significant compared with other years.2) The variation trend of organic carbon content in soil aggregates was as follows: 12 a＞18 a＞7 a＞3 a＞CK,and the organic carbon content of soil 1~0.25 mm granular aggregates was the highest.3) The contribution rate of soil aggregates to organic carbon was about 40% from ＞ 5 mm granular aggregates.Organic carbon storage of soil ＞ 5mm granular aggregates presented an increasing trend with rising age of the alfalfa plantations.The organic carbon storage of each particle size aggregates in 0~20 cm soil layer was higher than that in 20~40 cm soil layer with different planting years.