Dynamics And Driving Factors Of Soil Nematode Community In Monoculture Artificial Grasslands In Alpine Region

Soil nematodes are an important part of the ecosystem and play an important role in material circulation,energy flow and improvement of soil physical and chemical structure.In recent years,in order to alleviate the spatial imbalance of grassland utilization and the contradiction between grass and livestock,the establishment of artificial grassland in the Qinghai-Tibet Plateau is one of the main strategies for the restoration of degraded grassland,but the relationship between artificial grassland nutrients and soil nematodes is not clear.In order to explore the relationship between nutrient components and soil nematodes of artificial grassland,an artificial grass construction experimental plot was set up in Hongyuan County,northwest Sichuan from 2019 to 2020.The forage grasses Elymus nutans,Elymus sibiricus,Lolium multiflorum,Avena sativa,Medicago sativa and Vicia villosa are artificial grasslands.The natural grassland was used as the control plot.Five experimental plots of 5 m × 5 m were set up for each type of forage,and were observed continuously for 2 years.Collection of soil samples,plant samples,field data,and soil nematode surveys are carried out in late September every year to study the responses of soil nematodes to different artificial grassland nutrients.The main findings are:1.There were differences in forage biomass,nutrient content and soil physicochemical properties among different forage plots in artificial grassland.With the increase of cultivation years,the biomass,straw crude fiber,straw crude ash,root ether extract and root crude ash showed an overall increasing trend.It indicated that the increase of cultivation years was helpful for the accumulation of nutrient content of forage grass.2.A total of 60,848 soil nematodes were captured,belonging to 2 classes,9 orders,and184 genera,the community abundance was 4,894 individuals per 100 g of dry soil.The soil nematode community is composed of non-dominant groups;the common groups are 20 genera such as Aphelenchoides and Cephalobus,accounting for 62.23% of the total number of soil nematodes;Longidorella,Alaimus and other 164 genera were rare groups,accounting for 37.77% of the total number of soil nematodes.3.The results of principal component analysis(PCA)showed that among different forage species in the same cultivation years,only in 2019,the soil nematode community structure of the Vicia villosa plot was significantly different from that of the Elymus sibiricus and natural grassland.In 2020,each forage plot was significantly different.There were significant differences in soil nematode community structure between the two cultivation years of the same forage species,and the spatial variation of soil nematode community composition in 2020 was large.This indicated that the soil nematode community structure was affected by the type of forage and the years of cultivation.4.Soil nematode community density and diversity responded differently to forage species and cultivation years.There were differences in soil nematode community density and diversity among different pasture plots,but not significant;the soil nematode community abundance and diversity index showed an upward trend with the increase of cultivation years.The nematode abundances of Elymus nutans,Elymus sibiricus,Vicia villosa and natural grassland were significantly different between the cultivation years;the number of nematode groups in Avena sativa increased significantly with the increase of cultivation years;the nematode diversity of Avena sativa and natural grasslands also differed significantly between the cultivation years.5.The results of Redundancy analysis(RDA)showed that aboveground biomass,root total phosphorus and available potassium were the main factors affecting the composition and structure of soil nematode community.The results of multiple stepwise regression analysis showed that plant biomass,root total potassium,root total phosphorus and available potassium had significant effects on soil nematode community density and diversity.The effects of different environmental factors on the nutrient structure and ecological index of soil nematodes were different.The above research results show that soil nematodes are significantly correlated with plant nutrient content and soil physicochemical properties,and each trophic group is directly or indirectly affected by different nutrient components and soil physicochemical properties.The increase of cultivation years can promote the accumulation of soil organic matter in artificial grassland.It shows that the cultivation of artificial grassland can help improve plant traits and soil chemical properties,promote the growth and reproduction of soil nematodes,and enhance the stability of soil food webs.