不同土地利用与施肥管理下黑土团聚体颗粒有机碳分配变化

土地利用和土壤管理方式的变化强烈影响土壤结构及土壤有机碳的稳定机制。基于长期定位试验,通过分析土壤团聚体粒级及碳分布,以揭示和探讨不同土地利用和施肥管理下东北黑土团聚体颗粒有机碳分配特征及其稳定性机制。通过分析>0.25mm团聚体的变化,草地植被恢复和农田有机培肥团聚体稳定性显著提高。所有处理团聚体碳的分布趋势均表现为:>0.25mm团聚体>微团聚体>粉粘粒。草地粗颗粒有机碳总量和细颗粒有机碳总量均显著高于裸地和无肥处理(p<0.05),表明自然植被恢复可有效提高物理保护颗粒有机碳含量。农田有机培肥明显增加粗颗粒有机质(p<0.05),但并没有提高细颗粒有机质的量。物理保护颗粒有机碳占土壤总碳的比例为10.1%～18.6%,平均约15%。平均重量直径与粗、细颗粒有机碳的相关性达极显著水平(p<0.001),特别是与>2mm团聚体内各颗粒有机质组分碳的相关性更强(r≥0.9,p<0.001)。长期植被恢复和增施有机肥不仅可提高土壤碳库储量,并增强了土壤结构稳定性及土壤组分有机碳的物理性保护。

Particulate Organic Carbon Distribution in Aggregates Differing in Land Use and Long-term Fertilization in Black Soil

Changes in land use and soil management strongly impact soil structure and C stability.On the basis of long-term experiments,this study aimed to examine the distribution of particulate organic carbon(POM-C) in water-stable aggregates(WSA) and C stability under different land use and fertilizer management in black soil in northeast China.The mass distribution of >0.25 mm aggregates and mean weight diameter(MWD) were higher in grassland(GL) and organic amendment treatment(i.e.NPM) than in other plots.For all plots,aggregate associated C decreased in an order of WSA>0.25 mm>WSA0.053～025 mm>silt & clay.Grassland constituted significantly higher coarse POM-C and fine POM-C than bareland and no fertilizer(NF) plot(p<0.05),indicating that natural vegetation restoration strongly protected POM-C in aggregates.In cropland,organic amendment significantly increased coarse POM,but did not increase fine POM accordingly.Physically protected POM-C accounted for averaged 15% of total soil carbon ranging from 10.1% to 18.6%.Very strong correlation occurred between both coarse and fine POM-C and MWD(p<0.001),particularly within>2 mm aggregate(r≥0.9,p<0.001).In sum,long-term natural vegetation and organic amendment not only increased soil C stocks,but enhanced soil aggregation,and physical protection of soil C fractions.