Stoichiometric Characteristics And Adaptation Mechanisms Of Typical Karst Forest Plants In Microhabitats

Karst areas are mainly distributed in southern China,accounting for about 13% of China’s land area.The surface of this area presents a special geomorphological structure with a large number of exposed carbonate rocks,accompanied by strong karstification,which leads to serious soil erosion in the region,and the spatial distribution of microhabitats is highly heterogeneous.The complex and diverse conditions in the microhabitat inner light and water,uneven soil distribution and other factors make the environmental variability in the microhabitat strong.Hence,the growth of plants in this area are usually restricted by different degrees of environmental factors.In order to adapt to such an environment,plants form different adaptation strategies by adjusting their own nutrient content and changing their physiological structure.Therefore,this paper mainly analyzed the influence of different microhabitats on the stoichiometric characteristics of plants through the study of typical karst forest plant-litter-soil stoichiometric characteristics and plant leaf functional traits in different microhabitats.On this basis,principal component analysis(PCA)was adopted to reveal the survival strategies of plants in this region in harsh habitats.The main results were as follows:(1)In the microhabitats of soil surface,stone surface and stone ditch,the content of C in the leaves of different life-form plants were aiphylliums>evergreen shrubs>deciduous trees,N and P content were evergreen shrubs>deciduous trees>aiphylliums,and the K content was constant.evergreen shrubs>aiphylliums≈deciduous trees,the Ca content was deciduous trees>aiphylliums≈evergreen shrubs,and the content of Mg was evergreen shrubs>deciduous trees>aiphylliums.In each microhabitat,the nutrient distribution ratio among different organs of the same lifeform plant was shown as: the ratio of C,N,P,K content and Mg contents in the organs of aiphylliums was leaf>branch>trunk,and the Ca content was branch>leaf>trunk;the ratio of C,N,P,Ca,Mg content in the organs of deciduous trees was leaf>branch>trunk,and the K content was branch>leaf>trunk;the nutrient content ratio of each organ of evergreen shrubs was leaf>root> trunk.On the whole,in each microhabitat,the nutrient content of leaves of evergreen shrubs was higher than that of other life-form plants,and the nutrient content of plant leaves was the highest among the nutrient distribution ratios of various plant organs.(2)In soil surface microhabitat,aiphylliums,deciduous trees and evergreen shrubs were limited by P element;in stone surface microhabitat,aiphylliums and evergreen shrubs were restricted by N and P elements,and deciduous trees was restricted by P element;in stone gully microhabitat,aiphylliums were confined by N,P elements,and deciduous trees and evergreen shrubs were restricted by P element.The Ca content of plants in the stone surface microhabitat was higher than that of the other two microhabitats,and there was a certain degree of calcium and magnesium antagonism on the branches and trunks of various life-form plants.(3)From the correlation analysis of the stoichiometric characteristics between plants,litter and soil,there is a certain degree of nutrient migration in soil surface and stone surface habitats.Plants compensate for the lack of nutrient supply in the soil by absorbing nutrients from the litters,and the nutrient migration degree in the stone surface is relatively high;in the stone gully habitat,the nutrient migration degree is lower,and there are better water and nutrition conditions.(4)From the effect of microhabitats on the stoichiometric characteristics of different life-form plants,the type of microhabitats have no significant effect on stoichiometric characteristics of plants,while plant life forms have a significant effect on stoichiometric characteristics of plants.(5)From the perspective of different life-form plants,evergreen trees have higher leaf dry matter content and leaf density;evergreen shrubs have higher specific leaf area,leaf water content,N,P,K,Mg;deciduous trees have higher had higher net photosynthetic rate.From the perspective of the "leaf economics spectrum",evergreen trees are at the "slow investment return" end of the leaf economics spectrum,while evergreen shrubs are at the "fast investment return" end,and deciduous trees are in the middle between the two above belonging to the intermediate type.In this study,from the perspective of the adaptation of plants in different habitats,the plants on the soil surface tended to have a survival strategy with low stress resistance,resource acquisition and retention capabilities;the plants on the stone surface tended to have higher ability of stress resistance and resource utilization and maintain,but its growth level is low;the plants in stone gully tended to have a survival strategy with growing fast and having strong resistance and resource acquisition and maintenance ability.Thus,the stone gully habitat is more suitable for plant growth.