桂西北峰丛洼地农区耕作模式对土壤团聚体及其固碳效应的影响

Effects of Tillage Modes on Soil Aggregates and Carbon Sequestration in the Farming Areas of Karst Peak-cluster Depressions of SouthwestChina

桂西北峰丛洼地农区由于耕作干扰成为了潜在的石漠化风险区与碳源区,为评估不同耕作模式的石漠化风险与固碳效应,服务新时期石漠化治理与岩溶区碳汇评价工作。该研究以桂西北典型峰丛洼地农区——广西平果喀斯特生态系统国家野外科学观测研究站为研究区,以反映土壤稳定性与固碳效应的土壤团聚体及其固碳效率为指标,以退耕恢复灌草地(TGD)为对照,评价了当地主要耕作模式翻耕(玉米地,YMD)、少耕(甘蔗地,GZD)、免耕(火龙果地,HLG)的土壤团聚体稳定性及固碳效应。结果表明:(1)耕作模式深刻影响土壤团聚体组成及稳定性,随着耕作强度的增加,大粒级团聚体衰减明显,>10mm、>0.25mm粒级团聚体含量、平均重量直径(MWD)、几何平均直径(GMD)均呈TGD>HLG>GZD>YMD的分布趋势;同时,该趋势在时间稳定性方面同样存在。(2)土壤有机碳含量大小顺序为TGD>HLG>YMD>GZD,表明耕作会导致土壤有机碳的损失。(3)土壤大团聚体是土壤有机碳的主要固持者,土壤有机碳主要分布于>0.25mm的大团聚体中,其中>10mm团聚体含量与土壤有机碳含量呈极显著正相关关系。综上,免耕模式更利于保持土壤大粒级团聚体的数量、稳定性与有机碳含量,具有较低的石漠化风险和更好的固碳效应。

The peak-cluster depression of Northwest Guangxi,because of farming interference,has become a potential rocky desertification risk area and carbon source area.To eveluate the rocky desertification risk and carbon sequestration of different tillage modes and serve the rocky desertification control and carbon sink evaluation of karst area in the new era,thisstudy takes the typical peak-cluster depression farming area in NorthwestGuangxi,Guangxi Pingguo Observation and Research Station for Karst Ecosystems,Chinese Academy of Sciences as the research areas,taking the soil aggregate reflecting soil stability and carbon sequestration and its carbon sequestration efficiency as the index,and taking returning farmland to irrigated grassland(TGD)as the control,the soil aggregate stability and carbon sequestration of tillage(corn field,YMD),less tillage(sugarcane field,GZD)and no tillage(Pitaya field,HLG)were evaluated.The results showed that:(1)tillage pattern had a profound effect on the composition and stability of soil aggregates.With the increase in tillage intensity,the aggregate size decreased significantly,and the aggregate content,mean weight diameter(MWD)and geometric mean diameter(GMD)of>10mm and>0.25mm showed a trend of TGD>HLG>GZD>YMD;At the same time,this trend also exists in time stability.(2)The order of soil organic carbon content was TGD>HLG>YMD>GZD,indicating that tillage would lead to soil organic carbon loss.(3)soil aggregate is the main holder of soil organic carbon,and the soil organic carbon is mainly distributed in the large aggregate>0.25mm,and the content of soil organic carbon>10mm is positively correlated with the content of soil organic carbon.In conclusion,notillage mode is more beneficial to maintain the number,stability and organic carbon content of soil aggregates,and has a lower risk of rock desertification and better carbon sequestration.