| The alpine grassland on the Qinghai-Tibet Plateau accounts for 30%of the country's total area,and plays an important role in the development of my country's animal husbandry,the improvement of the ecological environment,and the protection of the safety of the ecosystem.However,due to the fragility and sensitivity of the grassland ecosystem in the alpine region,as well as the global climate change and human overgrazing and other factors,the grassland was seriously degraded,and the grassland was difficult to recover after degradation,which severely restricted the development of local animal husbandry and the ecological environment it was adversely affected,and artificial grassland can relieve the pressure of grazing to a certain extent.At present,there were few studies on the effects of artificial grassland on soil nematode communities and soil microorganisms,which had an adverse impact on the management of grassland ecosystems in alpine regions.Therefore,the study of the impact of different artificial pastures on soil organisms provided a scientific theoretical basis for the construction of artificial grasslands and ecological restoration and reconstruction of grasslands.In this paper,seven forage species of alpine region,including Poa crymophila,Elymus submuticus,Elymus breviaristatus,Elymus nutans,Puccinellia tenuiflora,Elymus sibiricus,Roegneria pauciflora were selected as the research objects,and the differences of soil physical and chemical properties,soil microbial biomass,soil enzyme activities,soil nematode communities and soil microbial communities under different forages were studied.The results are as follows:(1)Planting different artificial pastures significantly affected the soil microbial biomass and soil enzyme activities.The soil microbial biomass carbon content in Elymus submuticus and Elymus breviaristatus was significantly lower than that of Roegneria pauciflora,while the microbial biomass nitrogen was higher.The content of soil microbial phosphorus in Puccinellia tenuiflora was significantly higher than that of other pastures.There were significant differences in soil enzyme activity among the seven grasslands.Among them,the soil?-xylosidase activity of Poa crymophila(37.49 nmol·g-1·kg-1 dry soil)was significantly greater than that of Roegneria pauciflora(25.57 nmol·g-1·kg-1 dry soil);Soil cellobiohydrolase activity in Puccinellia tenuiflora,Elymus sibiricus,Roegneria pauciflora was significantly lower than that of Poa crymophila,Elymus submuticus,Elymus breviaristatus,Elymus nutans.The soil alkaline phosphatase activity in Elymus sibiricus and Roegneria pauciflora was significantly higher than that in Poa crymophila,but there was no difference in the activities of other several enzymes among different grassland types.The ratios of C:P enzyme and N:P enzyme in Poa crymophila were significantly higher than those of other grasslands.In addition,the stoichiometric ratio of soil enzymes was lower or higher than the global average.Vector analysis showed that soil microorganisms between different types of forage plantations were limited by phosphorus(vector angles were all>45°).(2)There were no significant differences in the Shannon index and dominance index of soil nematode communities among the seven grasslands.Both the SR richness index and Shannon-Wiener index were the largest in Roegneria pauciflora and Elymus vulgaris and Elymus brevifolia was the smallest.The maturity index showed that Poa crymophila was significantly higher than that of Elymus breviaristatus and Roegneria pauciflora,while the maturity index of the Plant Parasitic Index in Roegneria pauciflora was significantly higher than that in Puccinellia tenuiflora.The enrichment index and structure index were the largest in Elymus sibiricus,indicating that Elymus sibiricus has strong ability to resist external interference.The channel index was greater than 0.75,indicating that the decomposition of soil organic matter in each forage planting area was dominated by bacterial channels.The soil metabolic footprint indicated that the bacterial pathways of the poor-flowered in Roegneria pauciflora were stronger and the fungal pathways were weaker than that in Elymus submuticus and Elymus breviaristatus.(3)There are significant differences in the diversity index of soil bacterial communities under different pastures.Among them,the ACE and Chao1 index in Elymus submuticus were significantly higher than those of Elymus submuticus and Roegneria pauciflora;but there was no significant difference in the Shannon-Wiener and Simpson diversity indexes among different grasslands.In the fungal community,there was no significant difference in soil diversity index among seven grassland types.The dominant phylum of bacteria was Proteobacteria,Acidobacteria and Gemmatimonadetes.In the fungal community,the dominant phylum was Ascomycota.Redundancy analysis showed that soil water content and nutrient content were key factors affecting the differences in soil bacterial and fungal communities.In short,in the high-cold area,planting P.sibiricum and Tongde old awn wheat is beneficial to soil nematode diversity and grassland ecosystems.The planting of Elymus serrata has a positive effect on increasing the abundance and diversity of soil microorganisms. |
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