Daily dynamics effects of microclimate of two underlying surfaces in rocky desertification areas
As an ecologically vulnerable area with the strongest karst development in the world,the karst area in Southwest China exceeds 540,000 km2.Long-term human activities and frequent extreme climate have accelerated soil erosion,causing large areas of bedrock to be exposed on the surface;consequently,a rocky desert landscape with severely degraded vegetation came into being.Under the influence of the hot and humid monsoon climate,carbonate rocks underwent dissolution,which formed various heterogeneous underlying surfaces such as earth flatland and stone surface.The local microclimate differences caused by different underlying surfaces play an important role in regional vegetation restoration and ecosystem reconstruction.Current research on environmental factors in rocky desertification areas mainly focuses on water,soil and other aspects,while there is still a lack of research on microclimate of underlying surfaces.Taking two typical underlying surfaces(earth flatland and bare land)as the research objects,this study aims to explore the microclimate effects of heterogeneous underlying surfaces in rocky desertification areas.A long-term quantitative comparison in daily dynamics of near-surface temperature and humidity of these two underlying surfaces were conducted through simulation experiments.In rocky desertification areas,earth flatland is composed of polygonal rock masses exposed on the surface and patches of soil distributed inside,while bare land is normal land with no exposed rocks and no vegetation coverage.This study area is located in Puding county,Anshun City,Guizhou Province,where karst is strongly developed.The karst landform accounts for 84.27%of the county area with 60.55%of rocky desertification.The county has humid monsoon climate on the north subtropical plateau,with an annual average temperature of 15.1℃ and an annual rainfall of 1,378.2 mm.The annual total solar radiation fluctuates from 85.71 to 458.81 MJ·m-2.Preliminary field surveys found that there were large parameter variations in rock mass shape and size,and orientation of earth flatland.In order to improve the reliability and accuracy of the observation results,this study adopted in-situ limestone and concrete pouring technology to conduct simulation construction based on the average parameters of 30 earth flatlands that have been investigated.There were three replicates for each of the two underlying surfaces.To carry out long-term monitoring of temperature and relative humidity,high-resolution iButton DS1923 temperature and humidity recorders were installed at different heights(2 cm,40 cm and 80 cm)above the surface of the two underlying surfaces.All data analyses were performed in the R version 4.2.3.The functions of tapply and bartlett.test/var.test were used to test data normality and homogeneity of variances.If the data passed the test,one-way ANOVA would be used to conduct multiple comparisons of air temperature and humidity at different spatial heights.An independent sample t-test was used to compare the air temperature and humidity at the same spatial height on earth flatland and bare land.If the test failed,multiple sets of data would be applied for non-parametric testing and multiple comparisons through the kruskal.test function and PMCMRplus package.These two groups of data were applied for the wilcoxon rank sum test by the wilcox.test function.Daily dynamics of microclimate of bare land and earth flatland obviously differed on the spatial and temporal scales.When solar radiation was the strongest in summer,temperature at each spatial height of earth flatland was significantly higher than that of bare land(P<0.05),and the relative humidity was significantly lower than that of bare land(P<0.05),which led to warming and dehumidifying conditions.However,air temperature in the bottom space of earth flatland was significantly lower than that in bare land(P<0.05),and the relative humidity was significantly higher than that of bare land(P<0.05)from 10:00 to 16:00 in winter,which resulted in cooling and humidifying effects.The daily variation degree of microclimate in bare land and earth flatland was significantly different in response to different seasons.The daily temperature range of the upper layer of earth flatland was significantly higher than that of bare land(P<0.05)in summer,indicating that the earth flatland intensified the daily change of air temperature.However,the daily temperature and humidity range of the lower layer of the earth flatland was significantly lower than that of the bare land(P<0.05)in winter,showing that the earth flatland buffered the daily change of the microclimate.At present,bedrock-exposed areas of rocky desertification are under a more severe and changeable microclimate change background.Therefore,based on the differences in the microclimate effects of heterogeneous underlying surfaces,priority should be given to introduce early fast-growing karst plants to accelerate surface vegetation coverage and improve local microclimate conditions,which would play a positive role in buffering microclimate changes in rocky desertification areas and accelerating vegetation restoration.
rocky desertificationunderlying surfacemicroclimatetemperature and humidityvegetation restoration
万方数据
维普
