长期围栏封育对天山中部草地土壤有机碳及微生物量碳的影响

以天山中部中科院巴音布鲁克草原生态观测站三种类型草地长期（26 a）围栏封育样地为研究对象,通过野外调查取样结合室内分析的方法,研究了长期（26 a）围栏封育对草地土壤有机碳和微生物量碳含量的影响,结果表明：（1）围栏外（自然放牧条件下）,表层的土壤有机碳含量为高寒草甸（165.29 g·kg-1）〉高寒草甸草原（98.73 g·kg-1）〉高寒草原（83.54 g·kg-1）,微生物量碳含量依次为高寒草甸草原（181.70 mg·kg-1）〉高寒草甸（146.37 mg·kg-1）〉高寒草原（43.06 mg·kg-1）。围栏封育后,高寒草甸、高寒草甸草原、高寒草原表层土壤有机碳含量分别提高了11.37%、3.26%和2.21%;高寒草甸草原和高寒草甸微生物量碳含量分别增长2.89%和12.04%,而高寒草原降低40.36%。（2）从围栏内外土壤剖面来看,土壤有机碳、微生物量碳含量随着土壤深度的增加依次降低,微生物熵也随土壤深度的增加呈现降低的趋势。（3）微生物量碳含量与土壤速效钾、全磷含量达到极显著负相关（P〈0.01）,与速效磷含量达到极显著正相关（P〈0.01）,与土壤有机碳、全氮、全钾含量呈显著正相关（P〈0.05）与土壤速效氮含量正相关,但不显著。

Effect of Long-term Fencing and Grazing Exclusion on the Grassland Soil Organic and Microbial Carbons of Middle Tianshan Mountain

Grassland degradation occurs due to the long-term heavy grazing. The most common rehabilitation methods include fencing, sup- plemental seeding, fertilizer application and etc. Three types of grassland fenced for long-term（ 26 years ） grazing exclusion in Middle Tian- shan Mountains was sampled for analyzing the long-term effect on both soil organic and microbial carbons. The analysis of organic carbon adopts conventional method; and we use Chloroform fumigation extraction-TOC method to measure microbial carbon to mainly analyze the soil samples in the soil profile and the surface soil. The results indicated that organic carbon content in subsoil outside the fence（ under the condition of free grazing） in descending order is alpine meadow （ 165.29 g· kg-l ） 〉 alpine meadow steppe （98.37 g· kg-4 ） 〉 alpine steppe （ 83.54 mg· kg-l ）; whereas soil microbial carbon content ： alpine meadow steppe （ 181.70 mg· kg-1 ） 〉 alpine meadow （ 146.37 mg· kg 1 ） 〉 alpine steppe （43.06 mg· kg-l ）. With the treatment of fencing and grazing exclusion, organic carbon content in subsoil of alpine meadow, alpine meadow steppe and alpine steppe increased by 11.37%, 3.26% and 2.21% respectively; whereas microbial carbon content increased by 2.89% and 12.04% in alpine meadow steppe and alpine meadow respectively while decreased by 40.36% in alpine steppe. In terms of soil section inside and ontside the fenced areas, soil organic carbon and microbial carbon contents both decreased with increase of soil depth, so did Cmic/Corg. Microbial carbon content showed a very significant negative correlation with available K and total P in soil（P〈0.01 ）, a very significant positive correlation with available P（P〈0.01 ）, a significant positive correlation with organic carbon, total N and total K in soil（P〈 0.05 ）, and a positive correlation with available N in soil, but not significantly. With the analysis, this paper can provide basis for improving the grassland carbon sequestration potential and reforming degraded grassland.