| The permafrost region of Daxing ’anling Mountains is an important ecosystem type that is highly sensitive to global climate change.Permafrost degradation has become an essential element affecting the equilibrium and sustainable development of cold region ecosystems.Soil nematodes are widely distributed in terrestrial ecosystems and play a crucial part in maintaining ecological equilibrium,and regulating plant growth and energy flow.They can also serve as indicator organisms for permafrost ecosystem conditions and soil health.To understand the impact of different vegetation types on soil nematode communities and ecological environments in the permafrost environment of Daxing ’anling Mountains,this study conducted investigations on soil nematode communities of three representative plant species,including Carex subpediformis,Vaccinium uliginosum,and Betula platyphylla,in the Heilongjiang Huzhong National Nature Reserve and the Beiji Village in Mohe City in June and September 2021.The study aimed to clarify the impact of different vegetation types on soil nematode communities in the permafrost environment.By analyzing the changing trends of soil nematode communities in the permafrost environment,this study predicts the characteristics of changes in the permafrost ecosystem and provides basic data for the restoration and management of permafrost ecosystems.(1)The investigation of soil nematode communities in different vegetation types in the permafrost region of Daxing ’anling Mountains revealed that a total of 17,866 soil nematodes were captured,belonging to 47 genera,28 families,7 orders,and 2 classes,with an average density of 496 individuals/100 g dry soil.The dominant genera were of the genus Coslenchus and Cephalobus.The number of soil nematodes varied significantly among different vegetation types,with the highest number found in Betula platyphylla,followed by Carex subpediformis,and the lowest number found in Vaccinium uliginosum.The number of soil nematodes in Carex subpediformis gradually decreased,while the number in Betula platyphylla gradually increased as the vegetation growth stage changed.The variation in the number of soil nematode taxa in different vegetation types was not consistent,but the nematode population in June is higher than that in September.The soil nematode community structure in the three vegetation types differed significantly and decreased as the vegetation growth stage changed.(2)The analysis of diversity characteristic indices of soil nematodes in different vegetation types showed that Diversity characteristics vary among three vegetation types in different sampling sites.The diversity index and evenness index in the Huzhong sampling site were both highest in the white birch forest,and the dominance index was highest in the moss grass meadow.In contrast,the diversity index and evenness index in the Mohe sampling site were both highest in Carex subpediformis.The diversity index,evenness index,and richness index in the three vegetation types were higher in June than in September,and the impact of the vegetation growth stage on diversity and richness indices was more significant.(3)The analysis of functional structure characteristics of soil nematodes in different vegetation types showed that the number and proportion of each trophic group varied among different vegetation types.Among them,bacterial-feeding and plant-feeding nematodes were the dominant trophic groups in the permafrost environment,while fungal-feeding and omnivorous nematodes were relatively scarce.The soil nematode community in the three vegetation types was dominated by r-strategists,with the cp2 group being the dominant group and the cp3-5 groups being less abundant and more sensitive to permafrost degradation.The MI and PPI indices of the three vegetation types indicated that the moss grass meadow had a more stable ecological environment and was less disturbed,while the white birch forest was more seriously invaded by plant-feeding nematodes.The channel index(CI)values of the three vegetation types were all greater than 50,indicating that the decomposition of soil organic matter was primarily executed by fungus.Compared with the other two vegetation types,the moss grass meadow in the permafrost region of Daxing ’anling Mountains is more suitable for soil nematode community settlement.The three vegetation types in the permafrost region of Daxing ’anling Mountains are all in the D quadrant,indicating that the soil nutrients in the permafrost region of Daxing ’anling Mountains are low,the environment is stressed and the soil food web is degraded.(4)The redundancy analysis and pearson correlation analysis of soil nematode community structure and various indicators with soil environmental factors in different vegetation types showed that the content of soil physical and chemical properties varied among different sampling sites and vegetation types,and had different degrees of impact on soil nematode communities.Redundancy analysis showed that soil p H value,soil organic material,quick-acting phosphorus and quick-acting potassium were significantly correlated with soil nematode genera,and were the major environmental factors affecting soil distribution.Pearson correlation analysis showed that the selected soil physical and chemical properties,including soil organic material,total nitrogen,total phosphorus,total potassium,quick-acting phosphorus,quick-acting potassium,quick-acting nitrogen,soil p H value,and soil moisture content,had a significant impact on soil nematode community indicators.The relationship between soil nematodes and soil physical and chemical properties is complex and requires further research.The impact of the change in vegetation growth stage on soil nematode communities is more significant in the permafrost region of Daxing ’anling Mountains.Both Betula platyphylla and Carex subpediformis are more conducive to increasing soil nematode abundance and diversity,and the ecological stability of Carex subpediformis is higher.Through the analysis of various indicators of soil nematode communities,it was found that the overall ecological stability of the permafrost region has declined,and its ability to resist interference has weakened,which may be the result of the continuous degradation of the permafrost ecosystem. |
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