| The root system,as the hinge connecting the aboveground part of plants and the soil environment,plays an important role in the ecosystem.Karst slope,with highly heterogeneous eco-hydrological environment,is an important landscape type in the subtropical region.The native vegetation suitable for karst slope generally has the restrictive characteristics of calcium-dependent,and drought tolerance,and along he slopes positions vegetation growth would produce differentiation.And vegetation biomass(including aboveground and underground biomass)is a important representative index of the research status of karst vegetation productivity.Due to the high heterogeneity,the measurement of the vegetation biomass in the karst area soil environment is very difficult,which restricts the grasp of the karst area vegetation biomass and vegetation growth status of the study was to explore to karst slope in natural recovery.In this study,vegetation communities in the upper,middle and lower geomorphic parts of the naturally restored karst slopes were taken as the research object.With plant biomass as the breakthrough point,plant root biomass as the main line,supplemented by fine root morphological characteristics,we studied the root distribution characteristics in different positions along the karst slopes,coupled with abiotic factors such as environmental soil.Furthermore,based on this study,we analyzed and revealed the adaptive mechanism of natural restoration vegetation to environment in karst area.The main results were as follows:(1)The species diversity index of woody plants showed different changes in different position sites of karst slopes.The species richness index,shannon-Wynner index and Simpson index of woody plants were significantly different in different landforms(p<0.05),and the diversity index of middle slope was higher than that of upper slope and lower slope.The species diversity index of herbaceous plants was lower than that of woody plants(p>0.05).The result of species diversity of plant communities on karst slopes was middle>lower>upper.The results showed that the community species diversity was mainly related to the contents of organic matter,alkali-hydrolyzed nitrogen,available potassium and total nitrogen.(2)The aboveground total biomass of plant communities in different geomorphic positions was significantly different(p<0.05),and the biomass of downslope was significantly higher than that of upslope.The mean aboveground biomass of the plant community in descending was lower position(1980.78±1992.8 g/m2)>middle position(1594.18±742.13 g/m2)>upper position(934.07±856.41 g/m2).There was no significant difference in aboveground biomass between the two types of herbs and woody plants(p>0.05),but aboveground biomass of woody plants was downhill>uphill>middle slope,and aboveground biomass of herbaceous plants was middle slope>uphill>lower slope.The community gradually changed from the herbaceous community on the upper position of karst slope to the woody community on the lower position.The sequence of community succession was lower slope>middle slope>upper slope.(3)There was no significant correlation between root biomass and slope position,but a significant negative correlation with soil depth(p<0.05).The sequence of the value of root biomass was middle slope position(892.13±373.77 g/m2)>upper position(892.13±373.77 g/m2)>lower position(453.6±90.95 g/m2);The total root biomass,fine root biomass and coarse root biomass of the upper,middle and lower slopes decreased significantly with the increase of soil depth(p<0.05),and the root biomass of the surface soil(0-10 cm)was the highest,and the proportion of surface root biomass was 25.62%in the middle slope,38.81%in the lower slope and 39.10%in the upper slope.The root biomass was mainly affected by soil nutrient factors organic matter,alkali-hydrolyzed nitrogen,available potassium and total nitrogen and total phosphorus.The biomass of fine roots was mainly affected by organic matter,alkali-hydrolyzed nitrogen and available potassium.(4)There was no significant difference in root-shoot ratio among different landforms(p>0.05).However,the root-shoot ratio gradually increased along the slope,that is,up slope(0.5354±0.28728)>middle slope(0.2705±0.16123)>down slope.There was no significant correlation between fine root morphology and slope position,while root length density,root area density and root diameter showed significant differences with soil depth(p=0.000).The other three indexes,such as specific root length,specific surface area and root tissue density,did not reach significant levels with slope position and soil depth.The main parameters affecting fine root morphology were root length density and root area density,which were mainly affected by alkali-hydrolyzed nitrogen and gravel content in soil. |
PDF Full Text Request