Study On The Stoichiometric Characteristics Of Different Suitable Tree Species In The Dolomite Desert Area

Rock desertification in a dolomite-dominated karst is one of the most important rock desertification types in the globe and its treatments and controls can be easily neglected,leading to the difficulty of vegetation restoration.Based on the stoichiometric theory of ecology,the leaf,branches,fine roots,rhizosphere and nonrhizosphere soil stoichiometry characteristics of 10 woody species(Ligustrum lucidum?Cinnamomum camphora?Vitex negundo var.cannabifolia?Cladrastis platycarpa?Camptotheca acuminata ? Koelreuteria paniculata ? Melia azedarach ? Robinia pseudoacacia?Coriaria napalensis?Jasminum nudiflorum)are studied in late spring in a dolomite-dominated karst area,southwest China.The carbon(C),nitrogen(N),phosphorus(P)and potassium(K)contents and their stoichiometric ratio in each part are measured and analyzed to explore the nutrient distribution mechanism and adaptive strategy of these species to the dolomite-dominated karst regions.The study would provide an important theoretical reference for managing and controlling the dolomite rock desertification especially in species selection and it is helpful to the enrichment and development of ecological stoichiometry.The main conclusions of this study as follows:(1)The plant nutrient content of each part is ordered as leaf >branch > fine root and the stoichiometric ratio of them is observed as leaf < branch < fine root.The difference of nutrient content in many tree species reach to a significant level but the C and P content difference are not significant.There has a higher N content in fine toot,branch and leaf of the locust species and has the lowest C: N,C: P and C: K ratio.These results show that nitrogen fixation of tree species of Leguminosae has an advantage over other species in the dolomite rock desertification regions.For branch and leaf,there are significantly positive relationship between N and P content showing that N and P has a close relationship with strong synergistic effect.(2)Nutrient loss of rhizosphere soil can be significantly observed in the study area but there is a stronger synergistic effect observed in non-rhizosphere soil.The nutrient accumulation of rhizosphere soil for the Robinia pseudoacacia,Cladrastis platycarpa,camptotheca acuminata and Jasminum nudiflorum is obviously higher than other tree species.These species may improve soil physical and chemical characteristics in the dolomite-dominated karst area.(3)In general,the total nutrient content is lower in leaf and fine root but the K content shows a higher value in branches.The leaf N:P ratios range from 5.24 to12.82(<14).Similarly,the leaf N:K and K:P ratios are 1.26(<2.1)and 6.53(>3.4),respectively.These results imply that the plant growth may be limited by N and P together and N play a more important effect.(4)For the nutrient contents,the trend of them in each part is as follows: leaf >branch> fine root > rhizosphere soil>non-rhizosphere soil,but the K content is higher in the fine roots than in the branches.The results may mean that there is lower soil nutrient content and more efficient use in the dolomite-dominated karst area.The correlation coefficient of nutrient content between fine roots and leaf is lower than the correlation coefficient between fine roots and branches but it is higher than the correlation coefficient between leaf and branches.Interestingly,there is obviously a synergy between N and K content while there shows an antagonistic action between P and K content.The relation of nutrient content between soil and branches is lower than the correlation between soil and fine roots but higher than the correlation between soil and leaf.However,the nutrient content displays a more significant relationship between non-rhizosphere soil and each part of plant than between rhizosphere soil and each part of plant showing that there is seriously nutrient loss from the rhizosphere soil in the dolomite rock desertification regions.