垦殖对新疆绿洲农田土壤有机碳组分及团聚体稳定性的影响

Effects of cultivation on organic carbon fractionation and aggregate stability in Xinjiang oasis soils

土壤有机碳是土壤质量变化的重要指标,土壤活性有机碳组分在土壤质量变化方面发挥重要作用。采用有机碳分组技术,研究了干旱荒漠区自然土壤开垦对绿洲农田土壤有机碳活性组分及团聚体稳定性的影响。结果表明:低有机碳含量的自然土壤垦殖后,有利于干旱荒漠区绿洲棉田土壤有机碳的积累,且垦殖(0-5a)增加显著,年均增加在0.65gkg-1以上,上升幅度为76%-286%,5a后维持在相对平衡的水平;土壤活性有机碳、轻组有机碳在垦殖0-5a显著增加,平均增加72%和99%,5a后下降;颗粒有机碳则表现出垦殖0-10a明显增加,增加在275%以上,10a后下降;土壤水稳性团聚体含量随垦殖年限的延长显著增加,0-20a内较自然土壤提高了75%。垦殖可能是干旱区绿洲农田潜在碳汇的重要影响因素;但随垦殖年限延长,土壤有机碳活性组分下降,土壤质量又存在一定的退化风险。

Soil organic carbon is an important indicator of soil quality,and labile organic carbon fractions play an important role in soil quality development.In this study,fractionation of labile soil organic carbon was performed to evaluate the effects of cultivation practices on the changes of organic carbon and aggregate stability in soils of the desert area.The results showed that organic carbon content significantly increased in 1-5 years after the low organic matter natural soil was converted to cotton field,with an mean annual increase of 0.65 g kg^-1 or increased by 76%-286%.Soil organic C attained relative balance after 5 years of cultivation.Soil labile organic carbon（LOC）and light fraction organic carbon（LFOC）increased significantly in 1-5years,with an average increment of 72%-99%,but declined after 5 years of cultivation.Particulate organic carbon（POC）significantly increased in 1-10 years of in cultivation,with a maximum increase of 275%,and declined after 10 years of cultivation.Water-stable aggregates（WSA）in soil increased significantly with cultivation,up to 75% as compared with the original natural soil in 0-20 years.These results indicate that cultivation has an important influence on soil organic carbon pools of the oasis farmland.Long-term of cultivation of the desert soil tends to decrease labile organic carbon and subsequently may potentially cause degradation of soil quality,which merits further attention.