Thermal Buffering Effect Of Micro-topography Induced Habitat And Community Functional Diversity Variation In Loess Hilly Region

The topography of the loess hilly region is complex and changeable.It affects the redistribution of water,heat and nutrients,and has an important influence on the vegetation restoration and pattern,ecosystem process and function.Functional trait is the bridge linking organisms or ecosystems to the environment.Studying the change of the biological community functional traits with micro-topography is helpful for us to understand the influence of micro-topography habitat on ecosystem process and function and its role in regional biodiversity maintenance.In this study,we chosen natural grassland communities in Yanhe River Basin as the research objects,and selected three transect slopes covering different topographic habitats.We investigated the thermal buffering effect of micro-topographic habitats,and also studied the response of functional diversity(plant functional diversity,microbial functional diversity)to variations in micro-topography and soil factors.The purpose of this study was to determine the effect of micro-topography on the functional diversity of grassland communities in Loess Hilly region,and to analyze the association between plant functional diversity and soil microbial functional diversity,and to reveal the value and status of micro topography in vegetation restoration and biodiversity maintenance in this area.The conclusions are as follows:(1)Thermal buffering effect of micro topographic climate from regional ambienttemperatureMicro-topography induced micro-climate is different from regional climate,which can buffer the impacts of regional climate change to some extent.This study showed that although the temperature of each slope had a consistent change with time,the temperature changes between different slope aspects and positions was not completely synchronized.The micro-terrain climate had a certain buffer effect from the regional environmental temperature: The thermal buffering effect of micro-topography at ground 5cm height was generally 2-3 times higher than the above ground 150 cm height in the hottest month,the buffer capacity of the daily maximum temperature was 7-11? on shady slope,the buffer capacity of average daily temperature reached 2?;The thermal buffering effect of characteristic temperature at ground 5cm height was different between shady and sunny slope in the coldest month,the buffer capacity on shady slope was 2 to 4 times than Sunny slope.The buffer capacity of daily minimum temperature at the shady slope is between-1 and 3.5?,and a significant difference in position between the slope.The thermal buffering capacity of daily average temperature was between 4 and 6?,and the buffering capacity for daily temperature range was between 10 and 16?.Thermal buffering capacity was related to seasons,height,slope aspect and position.The thermal buffer effect of micro-topography changed with seasonal changes,thermal buffer capacity of the hottest month is higher than the coldest month strong.The nearer to the ground,the greater the temperature difference between different slope positions,the stronger the thermal buffering effect of the micro-topography microclimate.(2)The response of functional diversity of plant community to the change of micro-topographyThe micro-topographic change has an obvious effect on the features of community functional traits.The results showed that the leaf nitrogen content was significantly different among different slope positions,the leaf tissue density and the root tissue density both gradually reduced with the lowering of slope position,and no significant difference was found in other functional traits.The changes of slope directions generated the drastic differentiation on the species diversity and functional diversity.The difference of species diversity of plant community was large between the slope positions in shade slopes,even the difference was larger in south-facing slopes than the shade slopes.The change of slope position had some influence on the species diversity and functional diversity of plant community in the slope scale.Although it didn't reach a significant level,along the slope down,diversity showed a significant increase in the phenomenon.In the same slope,there were differences in diversity among different slope positions of the plant species,the species diversity was lowest in the top of the mound,the middle and lower slope position had the highest species diversity.Micro-topography habitat played an important role in maintaining regional species diversity and improving community functional diversity.(3)Response of soil microbial community functional diversity to micro-topographic changesThere were differences in functional diversity of soil microbial communities among different slope positions.The growth curves of the Average Well-Color Development(AWCD)were higher in the downslope position than that in the mid-slope position,which was higher than that in upslope position.Meanwhile,the functional diversity of soil microbial community at the downslope position was significantly higher than that in the mid-slope and upslope positions.There was a positive correlation between the microbial community richness(H)and homogeneous degree(D)and the total nitrogen content,whereas the dominance index(U)was negatively correlated with the total nitrogen content.Total carbon content,total phosphorus content,and pH have little effect on community structure and functional diversity.PCA showed that sugar,carboxylic acids,and polyphenol compounds contribute the most to soil microbial community functional diversity.The changes in soil moisture content along slope positions were the main factors affecting the soil microbial community functional diversity.There were no significant differences between two soil layers(0–10 cm and 10–20 cm).(4)The relationship between plant community biodiversity and micro-topography environmental temperatureThe characteristic temperature in the hottest month had significant or extremely significant negative correlation with community diversity and biological micro-topography environment.The increase in ambient temperature and temperature range in loess hilly areas is detrimental to maintaining slope biological diversity,but the thermal buffering effect of micro-topography can effectively mitigate the adverse effects of global warming on biodiversity in the region.Micro-topography habitat helps the loess hilly region to resist and adapt to global climate change.(5)The micro-topography induce habitat and biodiversity maintenanceIn the loess hilly region,micro-topographic habitat types are abundant and play a vital role in regional biodiversity conservation.This study showed that the micro-terrain habitat in the hilly-gully region can effectively buffer the regional climate change,which provided an important environmental basis for the maintenance of biodiversity.The species diversity and functional diversity of plant communities had the same response to micro-terrain changes.On the slope scale,although the influence of slope change did not reach the significant level,along the slope downward,the diversity increased obviously.While slope changes showed a strong differentiation effect on species diversity and functional diversity,the variation of species diversity in the slope of the sunny slope was larger than that of the shady slope.The functional diversity of soil microbial communities in the lower slope was significantly higher than that in mid-slope and the upslope.These results indicate that it is of great significance to understand the role of micro-terrain habitat in vegetation restoration and species diversity conservation and management.