新银合欢篱对紫色土坡地土壤有机碳固持的作用

土壤有机碳的固持对保持土壤肥力以及缓解全球温室效应具有重要意义。本研究通过田间定位试验，探讨了新银合欢（Leucaena Leucocephala）篱对10和15的紫色土农耕地（玉米地）和经济林地（油桃地）表层（0-20cm）土壤有机碳积累的影响。结果表明：种植3年的新银合欢篱的10和15农耕地、10经济林地土壤有机碳密度分别比相应的无植物篱的对照地提高41.53%、43.29%、32.15%。经济林处理土壤有机碳含量、有机碳密度、呼吸强度显著大于农耕地处理；10比15农耕地更有利于土壤有机碳、呼吸速率及微生物量碳提高；农耕地比经济林地更利于微生物生物量维持。各处理下坡比上坡更利于土壤有机碳蓄积，且土壤呼吸强度提高，但土壤微生物商基本相同。不同处理下，土壤有机碳与土壤理化性质相关性各不相同：定植新银合欢篱的10和15农耕地、10经济林地土壤有机碳与有机质含量、土壤微生物碳有极显著的相关性，与全钾呈正相关，与pH负相关；定植新银合欢篱的10和15农耕地呼吸强度与有机碳相关关系均达到了极显著性，10经济林地呼吸强度与有机碳显著相关；土壤微生物指标变化与有机碳的变化趋势一致,能反映土壤质量变化。阐明定植新银合欢篱利于土壤有机碳固持，且能增强土壤微生物活性，提高土壤质量。

Effect of Leucaena leucocephala on soil organic carbon conservation on slope in the purple soil area

Hedgerow has been widely used to reduce soil erosion.However,little information is available concerning the effect of hedgerow on soil organic carbon sequestration for various land utilization patterns in purple soil.Long-term field experiment was carried out to study the effects of Leucaena leucocephala hedgerows on soil organic carbon sequestration.Surface soil samples(0—20 cm) were collected from six south-facing standard runoff plots,with reddish-brown purple soil,were selected from Soil and Water Conservation Experiment Station of in Anju District,Suining City,Sichuan Province,China for experiment.Hedgerows(Leucaena leucocephala)were planted on contour in plotⅡ、Ⅳ、Ⅴ,and plotⅠ、Ⅲ、Ⅵ without hedgerows were selected as the control group.Plots Ⅰand Ⅱwere 10° cropland,plots Ⅲ and Ⅳ were 10° economic forest,and plots Ⅴand Ⅵ were 15° cropland.The crop planting model of cropland was spring-wheat and spring-corn continuous cropping,and economic forest land was nectarine colonization.Leucaena leucocephala hedgerows has been established since 2006.Soil organic carbon(SOC),respiration rate,soil microbial biomass carbon(SMBC),and soil nutrient were measured.Results showed that soil organic carbon density of 10° cropland cropland(2.85 kg/m2),15° cropland(2.37 kg/m2) and 10° economic forest land(3.27 kg/m2) with hedgerows planting for three years were 41.5%、43.3%、32.2% higher than those of control(2.01,1.79,2.28 kg/m2) respectively.Meanwhile,soil organic carbon content,organic carbon density and respiration rate in 10° economic forest land were more greater than that of 10° cropland.Moreover,10° cropland increased SOC content,respiration rate and SMBC than those of 15° cropland significantly;Results indicated that cropland was more efficient for conservation of SMBC than economic forest land.In addition,SOC and respiration rate on downhill were significantly higher than those of uphill for the same treatment.However,neither slope position nor land utilization patterns had significant effect on microbial quotient,which may imply that effects of cropland and economic forest on the soil conversation and did not differ significantly.The correlation between SOC and soil physicochemical properties varied with different treatments.Significant positive correlations were found between SOC and SMBC for 10° cropland,15° cropland and 10° economic forest land,while SOC and SMBC were negatively correlated with pH.In addition,significant positive correlations were also observed between respiration rate and SOC for 10° cropland,15° cropland with hedgerows,while significant correlation between the respiration intensity and soil organic carbon of 10° economic forest land with hedgerows.The variation of soil microbial parameters accorded with that of SOC,which may reflect a change of soil quality.The results indicated that Leucaena leucocephala hedgerows was beneficial to soil organic carbon sequestration,microbial activity enhancement and improving soil quality.