Dynamics of Soil Dissolved Organic Nitrogen and Inorganic Nitrogen Pool in Alpine Artificial Grasslands
This research was carried on alpine artificial grasslands in Qinghai Province. The soil dissolved organic nitrogen, soil inorganic nitrogen content and their season dynamics were analyzed, and the soil N-supplying capacity of different time was determined. This study will lay the foundation for alpine artificial grassland plants to absorb soil nitrogen. The results showed, (1) For dark chestnut soil of one year’s artificial grassland in Tongde County, soil NO3-N was most dominant and account for 54%~59% of the soil dissolved total nitrogen. The second was soil dissolved organic nitrogen and account for 22%~29%. The third is soil NH4+-N and only account for 17%. Soil NH4+-N content was increasing with growth season and up to maximum in September. Soil NO3-N was maximum in June and was decreasing with growth season. Soil dissolved total nitrogen and dissolved organic nitrogen was higher in turning green period and withering period than in thriving period. (2) For degraded alpine meadow soil of one year’s artificial grassland in Guoluo County, soil NO3-N and dissolved organic nitrogen were dominant and account for 49% and 43% of the soil dissolved total nitrogen respectively. soil NH4+-N only account for 8%. The season dynamics of soil NO3-N and NH4+-N in Guoluo County was similar with Tongde County. Soil dissolved total nitrogen and dissolved organic nitrogen was higher in July then was decreasing with growth season. So the dissolved organic nitrogen was a important compoant in alpine meadow soil, and its content was next to soil NO3-N and far higher than NH4+-N. (3) Compared with one year’s artificial grassland, soil available nitrogen was falling rapidly in three year’s artificial grassland. Such as soil NO3-N content decreased nearly 80%, soil NH4+-N decreased nearly 67%. Only there was no significant decline for soil dissolved organic nitrogen content. So, The decline of soil available nutrient was main reason for decline of artificial grassland productivity. (4) There was no significant difference for nitrogen content of different type among one year’s artificial grasslands with different forages. But in three year’s artificial grasslands, soil NO3-N contentseededPoa crymophila andPuccinellia tenuiflora was significant higher than that seeded other forages, and soil dissolved total nitrogen content seededPuccinellia tenuifloraandElymus sibiricus grasslands was significant higher than that seeded other forages. Therefore, plant species seeded would impact on soil nitrogen and different forage had difference for soil nitrogen requirement.
国家科技期刊平台
NSTL
万方数据
维普
