Responses Of Soil Nematode Community Structure Under Different Vegetation Restoration Modes In Rocky Desertification Control Area

The Karst region of southwest China is a typical ecologically fragile area.Its rock desertification problem has become an essential factor affecting the economic and social development of the region.As an indicator organism for restoring rock desertification ecosystem,soil nematode is a crucial indicator of ecological changes.In this research,soil nematode communities in six habitats,including native forest,Lolium perenne,Juglans regia,Lolium perenne,Juglans regia+Lolium perenne,and Zea mays,were investigated in January,April,and July 2021,respectively,in the demonstration area of rock desertification management in Bijie Salaxi.This paper systematically explores community composition,distribution,trophic taxa,community diversity,functional structure,and correlation between soil nematodes and environmental factors to lay the foundation for further work on soil and water conservation and ecological restoration.The main conclusions of this paper are:(1)The number of individual soil nematodes and the number of genera of taxa in the study area were relatively abundant,with a total of 16,478 soil nematodes captured,belonging to 94 genera in 13 orders and 49 families,with Aphelenchoides and Longidorella being the dominant genera.The number and distribution of soil nematodes differed between planting types(P<0.05).The number and individual density of soil nematodes increased under the restoration patterns of Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia + Lolium perenne.The seasonal variation was summer > spring > winter,with a decreasing trend in nematode numbers and increasing soil depth,showing prominent seasonal and aggregation characteristics.Planting Lolium perenne,Juglans regia,Lolium perenne,Juglans regia + Lolium perenne increased the number of nematodes to some.The planting of Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia+Lolium perenne increased the number of individual soil nematodes of taxa genera to a certain extent.(2)Under different planting patterns,compared to Juglans regia + Lolium perenne and Zea mays,Lolium perenne,Juglans regia,and Lolium perenne had higher diversity index,evenness index,nutrient diversity index and richness index,and lower dominance index;in season The indices for Lolium perenne,Juglans regia,and Lolium perenne were close to those of the native forest in spring and winter,and significantly higher than those of the native forest in summer.In general,the implementation of Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia+ Lolium perenne planting patterns in the area has enriched the diversity of soil nematodes to a certain extent,with Lolium perenne,Juglans regia and Lolium perenne planting patterns have a high nematode community diversity.Among them the increase in nematode community diversity was more pronounced in the Lolium perenne,Juglans regia and Lolium perenne models.(3)In this research,plant-parasites were the more abundant trophic group,followed by Predators-omnivore,while Fungivores and Bacterivores accounted for a smaller proportion.Seasonally,the number of each trophic group varied considerably,with the four trophic groups being higher in spring and summer than in winter,especially in summer when the number of Plant-parasites was significantly higher than the other trophic groups,and in winter when the number of Fungivores was substantially lower than the other trophic groups in the same period.The results showed that the distribution of soil nematode trophic groups was affected by different vegetation restoration patterns and seasonal changes.(4)Functional indices of soil nematodes show different patterns of variation in different vegetation restoration patterns and in different seasons.Compared with the native forest,the MI index,PPI index,and PPI/MI values of three habitats,Lolium perenne,Juglans regia,and Lolium perenne,showed minor variation from the native forest,and the soil ecosystem was more stable.In the four different vegetation restoration models,Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia+Lolium perenne,the MI index was higher in Lolium perenne,Juglans regia,and Lolium perenne than in Juglans regia+Lolium perenne.In comparison,the PPI index and PPI/MI values were lower.Overall,Lolium perenne,Juglans regia,and Lolium perenne have higher soil ecosystem stability,better resistance to external disturbances,and better vegetation restoration.(5)The diversity indices of soil nematodes were significantly correlated with soil water content and organic matter(P<0.05),the functional indices of nematodes were highly significantly associated with total phosphorus content(P<0.01),and the number of nematode individuals was also positively correlated considerably with fast-acting phosphorus and fast-acting potassium(P<0.01),indicating that soil water content,organic matter,total phosphorus,fast-acting phosphorus,and fast-acting potassium had a significant effect on The results showed that soil water content,organic matter,total phosphorus,fast-acting phosphorus,and fast-acting potassium has a substantial impact on soil nematodes.The relationships between soil nematode indicators and environmental factors are complex,and their intrinsic interrelationships need to be further investigated.The study shows that implementing Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia + Lolium perenne planting patterns in this area has increased the number and diversity of soil nematode individuals to a certain extent,which is conducive to the conservation of soil nematode diversity.At the same time,the functional indices also show that their soil ecosystems are more stable and more resistant to external disturbances,reflecting that the ecological restoration of rock desertification has achieved better results.The planting pattern of Lolium perenne,Juglans regia,Lolium perenne,and Juglans regia+Lolium perenne indicates that it is a better model to be adopted for the control of rock desertification in the region,which is of reference for the ecological management of rock desertification in the broader area and its neighboring regions.