A Preliminary Study Of Geographic Distribution Patterns And Driving Factors Of Insect Diversity In Northern Grasslands

The geographical distribution pattern of biological diversity is one of the key subjects of biogeographic research,and the loss of biodiversity is one of the major problems faced currently by humans.In order to solve the problem,ecologists research from different scales.The distribution pattern of biodiversity has become one of the most important issues that ecologists are concerned about in order to gain more understanding of the causes of biodiversity loss.As a major component of terrestrial ecosystems,grassland is influenced by human factors and climate change,which leads to the significant reduction of the diversity of grassland insects,resulting change in the diversity distribution pattern of the grassland.However,the deeply study is rare about grassland insect diversity.Although there is related hypotheses to reveal the mechanism of biodiversity distribution pattern,there are few explanation about the distribution mechanism of grassland insect diversity.Therefore,the study of distribution pattern of insect diversity is important in temperate steppe of North China.It not only enriches the theory of biodiversity,but also has important theoretical significance for the protection of insect diversity.At the regional scale,insect is the subject of this study.We investigated on insects,vegetation and climate in 40 research sites of northern temperate grassland,this paper analyzes the geographical distribution pattern of temperate insect diversity in northern China and discusses the effect of climatic factors and vegetation on the geographical distribution of insect diversity.The main results and conclusions are as follows:(1)With the variation of the latitude and longitude,the insect diversity of the northern temperate meadows showed a certain distribution pattern.With the increase of latitude,the diversity and abundance of insects increased;and with the increase of longitude,the diversity of insects increased first and then decreased.In grazing grassland,the diversity of insects increased with the increase of latitude.In fenced grassland,there no significant distribution of insect diversity,but the abundance of insects is increased with the increase of latitude.(2)Vegetation characteristics showed significant changes with latitude and longitude.With the increase of latitude,plant species richness gradually increased,showing a monotonous increasing trend;Plant Shannon-Wiener index changed with a "U".With the increase of the longitude,plant Shannon-Wiener index,Simpson index and Pielou index changed with "inverted U".But total plant biomass and grass biomass showed an increasing trend along longitude.Under grazing conditions,the plant species richness increased significantly with the increase of latitude.With the increase of longitude,the plant Shannon-Wiener index,Simpson index and Pielou index changed with "U".But the grass biomass increased along the longitude.Under enclosure conditions,total plant biomass and grass biomass increased with longitude.(3)Climate factors change significantly with changes of latitude and longitude.In grazing,fenced and other grassland,the annual mean temperature,maximum temperature,minimum temperature,isothermality,mean temperature of driest quarter,mean temperature of coldest quarter,min temperature of coldest month,solar radiation and wind speed significantly decrease with the increase of latitude.But temperature annual range,temperature seasonality,precipitation of wettest quarter,precipitation seasonality and precipitation of warmest quarter significantly increase.However,max temperature of warmest month grazing land decreases but precipitation of wettest quarter and precipitation of warmest quarter increase,and precipitation of driest quarter,annual precipitation and precipitation of coldest quarter show a secondary change with the increase of latitude in all kinds of pilot grasslands.What's more,mean diurnal range,isothermality,solar radiation and wind speed significantly decrease with the increase of longitude in all kinds of pilot grassland and grazing land;at the same time,mean diurnal range,isothermality and solar radiation will decrease significantly in fenced grassland.However,precipitation of wettest month,precipitation of wettest quarter,precipitation seasonality,annual precipitation and precipitation of warmest quarter increase significantly in grazing land,fenced grassland and all kinds of pilot grasslands,and max temperature of warmest month increase significantly as well in all kinds of pilot grasslands.Annual mean temperature,maximum temperature,minimum temperature,mean temperature of driest quarter,mean temperature of wettest quarter,mean temperature of coldest quarter,max temperature of warmest month,min temperature of coldest month,and mean temperature of warmest quarter show a secondly change with the increase of longitude in grazing grassland,fenced grassland and all pilot grasslands.In addition,temperature annual range in all pilot grassland and wind speed in fenced grassland also show a secondly change.(4)Climatic conditions and vegetation had significant effects on the geographical distribution pattern of grassland insect diversity.Through regression analysis,we found that plant species richness,Shannon-Wiener index,plant height,temperature seasonality and temperature annual range had a positive effect on insect abundance,species richness,Shannon-Wiener index and effective diversity;annual mean temperature,maximum temperature of warmest month,minimum temperature of coldest month,mean temperature of wettest quarter,mean temperature of driest quarter,mean temperature of warmest quarter,mean temperature of coldest quarter,minimum temperature and maximum temperature had a negative effect on insect abundance,species richness,Shannon-Wiener index and effective diversity.In grazing grassland,with the increase of plant species richness,Shannon-Wiener index,temperature seasonality and temperature annual range,the insect species richness and effective diversity increase;with increase of the annual mean temperature,maximum temperature of warmest month,minimum temperature of coldest month,mean temperature of wettest quarter,mean temperature of driest quarter,mean temperature of warmest quarter,mean temperature of coldest quarter,minimum temperature and maximum temperature,and the insect species richness and effective diversity reduced.In fenced grassland,plant species richness,plant Shannon-Wiener index,temperature seasonality and temperature annual range had a positive effect on insect species richness,Shannon-Wiener index and effective diversity;however,annual mean temperature,maximum temperature of warmest month,minimum temperature of coldest month,mean temperature of wettest quarter,mean temperature of driest quarter,mean temperature of warmest quarter,mean temperature of coldest quarter,minimum temperature and maximum temperature had a negative effect on insect species richness,Shannon-Wiener index and effective diversity.Mean diurnal range,solar radiation had a negative effect on insect abundance;however,annual precipitation,precipitation of wettest month,precipitation seasonality,precipitation of wettest quarter and precipitation of warmest quarter had a positive effect on insect abundance.In summary,this paper clarifies the basic laws of the distribution of insect diversity in temperate grassland in northern China.With the increase of latitude,the diversity and abundance of insects increase as well;with the increase of longitude,insect diversity increases first and then decreases.The diversity of insects in grazing grassland increases with the increase of latitude and the abundance of insects in fenced grassland increases with the increase of latitude.In addition,this paper also reveals the effects of climate and vegetation on the distribution pattern of grassland insect diversity.The increase in the annual variation of precipitation and temperature can significantly increase the diversity and abundance of insects.The diurnal variation of solar radiation,temperature,and mean diurnal range can significantly reduce insect diversity and abundance.The diversity and the height of plants significantly increase the diversity of insects,further verifying the correctness of the resource-intensive hypothesis.However,the biomass of grasses significantly reduces the diversity of insects.This research can not only deepen the understanding of grazing disturbance on the maintenance of the distribution pattern of grassland insect diversity,but also enrich grassland ecology theory and biodiversity theory.