不同利用方式对小针茅荒漠草原土壤活性有机碳的影响

通过围封、3个放牧梯度[0.50羊单位/hm²(G_0.50)、0.94羊单位/hm²(G_0.94)、1.25羊单位/hm²(G_1.25)]和开垦5种不同的处理条件下,对内蒙古小针茅荒漠草原土壤总有机碳、水溶性有机碳、易氧化有机碳、微生物量碳含量和土壤基本理化的影响开展野外监测试验。结果表明,1)不同利用方式下,小针茅荒漠草原土壤总有机碳、全氮、全磷、碳氮比均表现为围封>G_0.50>G_0.94>开垦>G_1.25。其中围封区的土壤有机碳含量、全氮含量显著高于G_0.94、G_1.25和开垦区(P<0.05),随着放牧强度的增加,土壤有机碳、全氮、全磷、碳氮比均呈现逐渐降低的趋势。2)开垦区和放牧区土壤表层(0~20 cm)水溶性有机碳、易氧化有机碳、微生物量碳含量,均显著低于围封区(P<0.05);在放牧区,随着放牧强度的增加土壤活性有机碳含量均逐渐降低。3)围封4年后小针茅荒漠草原土壤活性有机碳占总有机碳的比例提高,放牧和开垦使活性有机碳的比例下降。其中,围封区的土壤微生物量碳比例显著高于G_0.94、G_1.25和开垦区(P<0.05),较G_0.50、G_0.94、G_1.25和开垦区分别增加了0.26,0.53,0.66和0.43个百分点。4)土壤总有机碳、水溶性有机碳、易氧化有机碳、微生物量碳含量均具有显著(P<0.05)或极显著(P<0.01)的正相关关系,土壤活性有机碳组分与土壤理化性质具有密切的关系。

Effects of different land-use types on soil active organic carbon in the Stipa klemenaii desert steppe of Inner Mongolia

In order to explore variation in the contents and components of soil active organic carbon under differ-ent land-use types in the Stipa klemenaii steppe of Inner Mongolia,five field treatments were studied.These treatments included three grazing intensities,0.50 sheep/hm2 (G0.50 ),0.94 sheep/hm2 (G0.94 )and 1.25 sheep/hm2 (G1 .25 ),as well as one fenced enclosure and one tract of reclamation land.Analysis was undertaken to de-termine the contents of soil organic carbon (SOC),soil dissolved organic carbon (DOC),soil readily oxidizable organic carbon (ROC),soil microbial carbon (MBC)and soil physical and chemical properties:total nitrogen (TN),total phosphorus (TP),and carbon nitrogen ratio (C/N).The results showed that the contents of SOC,TN,TP and C/N were in the following order:enclosure>G0.50 >G0.94 >reclamation>G1 .25 .The con-tents of soil organic carbon and TN of the fenced enclosure were significantly higher than that of G0.94 ,G1 .25 and the reclamation land (P <0.05).The contents of SOC,TN,TP and C/N showed a gradually decreasing trend with the increase of stocking rates.Grazing and reclamation significantly decreased the contents of DOC,ROC and MBC when compared to enclosure (P <0.05 ).The contents of SOC and soil active organic carbon de-creased gradually with the increase of stocking rates.In general,the allocation proportion of active organic car-bon increased in 0-20 cm soil layers after 4 years of fenced enclosure in the S .klemenaii steppe,whereas it decreased after grazing and reclamation.The MBC/SOC of the fenced enclosure was significantly higher than that of grazing and reclamation (P <0.05).The contents of SOC,DOC,ROC and MBC had a significant posi-tive relationship with each other (P <0.05).Soil active organic carbon and soil physical and chemical proper-ties had a close relationship.These results indicate that fenced enclosure enhances soil quality and improves the S .klemenaii steppe environment.