不同利用方式下草地土壤理化性质及碳、氮固持研究

Study on soil physical and chemical properties and carbon and nitrogen sequestration of grassland under different utilization modes

为探究退化的天然草地与人工草地在土壤理化性质,碳、氮变化以及固碳效应等方面存在的差异,本研究通过野外取样与室内实验相结合的方法,在内蒙古自治区的阿鲁科尔沁旗选择具有代表性的天然草地、放牧人工草地以及刈割人工草地为研究对象,进行了实验区土壤水分含量、土壤容重、土壤微生物含量以及土壤养分的测定。通过NDVI值代表3种类型草地的生长状况,整体上看,不同利用方式下草地的生长状况为:刈割人工草地>放牧人工草地>天然草地;土壤含水量在0~20 cm从高到低为:放牧人工草地>刈割人工草地>天然草地,且差异均表现为显著(P<0.05);放牧人工草地的全碳全氮含量均为最高,在10~30 cm放牧人工草地和天然草地的全碳含量显著高于刈割人工草地(P<0.05),放牧人工草地0~10 cm的土壤全氮含量为(0.88±0.11)g·kg^(-1),显著高于天然草地和刈割人工草地(P<0.05);3种草地的土壤微生物量碳、氮含量的大小表现为:放牧人工草地>刈割人工草地>天然草地,且在0~10 cm放牧人工草地的土壤微生物量氮含量为(28.45±8.30)mg·kg^(-1),显著高于天然草地和刈割人工草地(P<0.05);此外3种草地类型的土壤碳、氮贮量表现为:天然草地>放牧人工草地>刈割人工草地,在10~30 cm放牧人工草地和天然草地的土壤碳、氮贮量均显著高于刈割人工草地(P<0.05),放牧人工草地表现为碳、氮固持,而刈割人工草地均表现为碳、氮流失,且随着土壤深度的增加,天然草地和刈割人工草地的碳、氮贮量均呈逐渐下降的趋势。由此可见,人工草地的建立以及对草地实施播种、灌溉等合理的人为干预将有效地提高土壤质量和草地生长状况,并且一定程度上影响土壤的碳、氮固持能力。

This research investigated the effects of natural grassland and artificial grassland degradation on soil physical and chemical properties,in particular the change in carbon and nitrogen contents and carbon sequestration.Representative areas of natural grassland,grazed artificial grassland and mown artificial grassland in Ar Horqin Banner,Inner Mongolia,were selected for study.Parameters measured in the study area were soil moisture content,soil bulk density,soil microbial content and soil nutrient levels.Growth status of the study sites was also evaluated using the NDVI value and in general the ranking for growth status under the different utilization modes was:mown artificial grassland>grazed artificial grassland>natural grassland.Soil water content in the 0-20 cm depth ranked:grazed artificial grassland>mown artificial grassland>natural grassland,and the differences were significant(P<0.05).The total carbon and total nitrogen contents in the grazed artificial grassland were the highest.The total carbon contents in the grazed artificial grassland and natural grassland for the 10-30 cm soil depth were significantly higher than that of the mown artificial grassland(P<0.05).The total soil nitrogen content of the grazed artificial grassland for the 0-10 cm soil depth was(0.88±0.11)g·kg^(-1),which was significantly higher than those of the natural grassland and the mown artificial grassland(P<0.05).The soil microorganism carbon and nitrogen content in the three grassland types ranked:grazed artificial grassland>mown artificial grassland>natural grassland.The soil microorganism nitrogen content of the grazed artificial grassland for the 0-10 cm depth was(28.45±8.30)mg·kg^(-1),which was significantly higher than values in the natural grassland and mown artificial grassland(P<0.05).Soil carbon and nitrogen storage for the three categories of grassland ranked:natural grassland>grazed artificial grassland>mown artificial grassland,and soil carbon and nitrogen storage of natural grassland and grazed artificial grassland for the 10-30 cm depth were significantly higher than that of mown artificial grassland(P<0.05).The performance characteristic of grazed artificial grassland was soil carbon and nitrogen accumulation,while that of mown artificial grassland was carbon and nitrogen loss.In addition,with increase in soil depth,the carbon and nitrogen storage of natural grassland and mown artificial grassland show a decreasing trend.Thus it can be seen that the establishment of artificial grassland and human intervention such as seeding and irrigation will effectively improve soil quality and grassland growth status,but to a certain extent there may be a negative effect on soil carbon and nitrogen sequestration potential.