Research On The Relationship Between Plant Communities And Soil Nematode In The Alpine Grassland Of The Tibetan Plateau

Soil nematodes are an important component of grassland ecosystems and are the most active organisms in plant rhizosphere soil.It is often regarded as the main consumer in grassland ecosystems and is closely related to grassland productivity.In recent years,researches on the effects of plant communities on soil nematode communities and their relationships have been valued.Therefore,this paper takes plant and soil nematodes as research points,analyzes the characteristics of the changes in the structure of plant and soil nematode communities under conditions of temperature increase,grazing,and degradation,and discusses the diversity of ecosystems of plants and soil nematodes in the Qinghai-Tibet Plateau grassland under natural and human disturbance The relationship between sexual and functional changes is expected to provide some theoretical basis for the restoration and development of alpine grassland.The main research results are as follows:(1)13,264 soil nematodes were isolated from the 265 soil samples of the alpine grassland on the Qinghai-Tibet Plateau,which belonged to 2 classes,6 orders,16 families and 34 genera,with an individual density of 64 to 996 per 100 g of dry soil.Soil nematodes decrease from top to bottom in the soil and have obvious surface aggregation.(2)Under the temperature increase range of 0~0.45℃,the plant species increase as the temperature rises;as the temperature increases,the plant species decrease.When the warming temperature reaches a maximum of 1.57℃,the plant species exhibits the lowest performance.The plant community in a warming zone has the highest diversity and stability,and the plant in D warming zone has the lowest diversity,and its plant community tends to be singular.It shows that the plant species can be increased in a certain temperature range.If the temperature is too high,the plant species will be reduced and the stability of the plant community will be reduced.At the same time,with the extension of time,the plant community’s adaptability to warming gradually increased.The longer the warming time,the more stable the plant community.(3)The number of soil nematodes under different temperature gradients: A(1120/100 g dry soil)> D(1022/100 g dry soil)> B(991/100 g dry soil)> CK(966/100 g dry soil)> C(881/100 g dry soil).The diversity index H ′ and uniformity index J′ of A warming circle are the highest,the warming circles B and C are lowest,and the dominance index λ is opposite(P <0.05).The results showed that the soil nematode community diversity and stability were the highest in the A warming zone,the B and C warming zones were lower,and the soil nematode community structure tended to be singular.The longer the warming time,the less the number of soil nematodes,but the effect of the soil nematode diversity index on the warming time was not obvious.Analysis of the functional structure of soil nematode communities: The relative abundance of fungal nematodes(Ba)was significantly different between CK and A warming circles(P <0.05).The decomposition of soil organic matter was mainly bacterial channels;The WI index is the highest,and the B warming circle is the lowest,indicating that the soil fertility in the A warming circle is significantly higher than that in the B warming circle,and the A warming circle is beneficial to the growth of microorganism-eating nematodes.,Indicating that the growth of above-ground vegetation is weaker than other treatments;the MI index under different treatments: A> D> CK> C> B,indicating that increasing the temperature has caused a certain degree of change in the soil environment.The above results show that warming has no effect on the decomposition pathway of soil organic matter,and appropriate warming temperature will increase the growth of above-ground vegetation,enhance soil fertility,and increase the diversity of soil nematode communities,which is conducive to the growth of microorganism-eating nematodes.(4)Under simulated grazing management,H′ and J′ are higher than enclosure,λ is lower.It can be seen that plant community diversity and stability are higher than enclosure under grazing management.Grazing reduces the number of soil nematodes and has a significant effect on the number of soil nematodes between 0-10 cm.Grazing management measures indirectly affect the stability of soil nematode communities by affecting plant communities,and at the same time they will have a certain impact on the correlation between soil nematodes and plant communities.It has no significant effect on the ecological index of soil nematodes,and significantly affects the number of bacterial feeding nematodes(Ba),phytophagous nematodes(Pp)and omnivorous/predatory nematodes(Op).(5)The number of soil nematodes under the four types of grassland: Kobresia humilis meadow(968/100 g dry soil)> Kobresia tibetica meadow(638/100 g dry soil)> Potentilla fruticosa shrub(541/100 g dry soil)> Carex atrofusca meadow(171/100 g dry soil).J diversity and uniformity were the highest,H was the lowest,and the dominance index was the opposite,indicating that the H soil nematode community tended to be singular,while the J soil nematode community diversity and stability were higher than other plant communities.Analysis of the functional structure of soil nematode communities: The four types of grassland are mainly Pp and Ba.The decomposition of organic matter in soils A and Z is dominated by bacterial channels,J is dominated by fungal channels,and H is completely degraded by bacteria.H gas The Leska index has the highest WI and the lowest WI,indicating that the transition from the alpine swamp meadow to the alpine shrub meadow,the soil fertility status of the alpine meadow is continuously decreasing,and the swampy meadow is conducive to the growth of microorganism-eating nematodes.Grassland type maturity MI index: Kobresia humilis meadow > Kobresia tibetica meadow > Potentilla fruticosa shrub > Carex atrofusca meadow,indicating that the lower the MI index,the soil environment changes with the succession of plant communities.At the same time,the number of soil nematodes,nutrient groups and functional diversity are all related to plant species diversity.(6)Alpine meadow degradation reduces plant species,reduces plant species diversity,and decreases plant community stability;while alpine grassland degradation increases plant community species composition,plant communities H′ and J′ increase,λ decreases,and plant communities tend to stable.H′ and J′ in alpine meadow are higher than alpine steppe,λ is lower than alpine steppe,the species diversity and plant community stability of alpine meadow are higher than alpine steppe.(7)The number of soil nematodes under different treatments: degraded alpine meadow(1009/100 g dry soil)> native alpine meadow(210/100 g dry soil);native alpine grassland(673/100 g dry soil)> degraded alpine grassland(211/100 g dry soil).The number of soil nematodes in alpine meadow is higher than that of grassland.There were no significant differences in soil nematodes H ′,J ′ and λ in degraded alpine grassland(P> 0.05).Grassland degradation did not change the soil organic matter decomposition pathways,and all of them were mainly bacterial channels.The number of Pp decreased and the amount of Ba increased.The PPI index of alpine steppe is lower than that of alpine steppe,which indicates that the growth of above-ground vegetation in alpine steppe is weaker than that of alpine steppe.The MI index under different treatments: YD <TD <TY <YY,indicating that grassland degradation and changes in grassland types will change the soil environment.At the same time,grassland degradation will change the relationship between soil nematode population,ecological index and functional diversity index and plant communities.