Ecological Stoichiometry Of Dominant Tree Species In Natural Secondary Forests In Limestone Mountains Of Northern Guangdong Province

The ecological adaptability and ecological response and regulation mechanism of forest plants to special habitats in limestone areasis the key scientific issuesthat must be clarified in the restoration and reconstruction oflimestone forest degraded ecosystems.In this paper,6 kinds of dominant tree species in natural secondary forests in limestone mountain as the research objectin order to study the plant growth,nutrient cycling and adaptive strategies to the special habitats,the determination of forest soil,in tree root zone,root and leaf C,N,P,K,Ca,Mg six kinds of nutrient elements,using ecological chemometrics methods for comprehensive analysis of the different species of soil,root and leaf nutrient content and its metering characteristic,and the synergy between soil,root and leaf were discussedduring the limestone vegetation growth.The main results are as follows:(1)The contents of C,N,P,K,Ca and Mg in soil of different tree species were different,the element contentofsoil C,N,K and Mgin Sapium rotundifoliumwere significantly higher than that of other tree species in the soil,the content ofP,Ca in Liquidambar formosana and Zenia insigniswere the highest-level.O n the whole,the content of C,N,P,K in the soil were dispersed in a small degree,in some degree of interspecific dispersion between the content of Ca and Mg was relatively large.The content ofN and the ratio of N/Pamong the soil shows greatly linearrelationship,so as tothe content ofC and the ratio ofC /P in the soil.(2)The contents of C,N,P,K,Ca and Mg in the roots of different tree species were different,overall,the rank ofthe 6 nutritive elements averageamountin the roots is: C > Ca >N > K > Mg > P.The degree of interspecific dispersion among the content of Ca and Mg elements in the root system wereboth obvious.While the degree of interspecific dispersion among other elements is relatively small.The contentof C in Lindera communiswere the highest-level,thecontent of N and Mg elements inSapium rotundifolium were thehighest-levelamong the six species of trees,the contentof P and K in Cinnamomum bodinieri were the highest-level,the content of Ca in Liquidambar formosana and Sapium rotundifolium werethe highest-level.O verall,the Ca,Mg element among theroots discrete degree were relatively large,other elements between the discrete degreewere relatively small.The ratio of C/K,C/P,Ca/K and Ca/Mg of the roots in Liquidambar formosanawere the highest-level,the ratio of C/P,K/P and K/ Mg of the rootsin Zenia insigniswere thehighest-level,theratio of N/P,N/K of the roots in Sapium rotundifolium were the highest-level,the ratio ofCa/K,Ca/Mg and K/Mg of the roots among the discrete degree were relatively large.There was a significant linear negative correlation between C elementand the ratio of C/N elementin the roots,there was a significant linear negative correlation between N element and the ratio of C/Nelementin the roots,the ratio of C/Pelement was also decreased linearly with the increase of the content of P in the roots.(3)The contentof C,N,P,K,Ca and Mg in the plant leaves of different tree species were different.As a whole,the rank ofthe 6 nutritive elements amountin the leaves were: C > Ca > N > K > Mg > P,and the nutrient content was Ca> K> Mg.The content of C inLindera communisand Cinnamomum camphora werethe highest-level,the content of N in Liquidambar formosanawerethe highest-level,the content of P in Zenia insignis and Celtis sinensiswere the highest-level,and the content of K in Cinnamomum camphorawere the highest-level,the content of Ca in Celtis sinensiswere the highest-level,the content ofMg in Zenia insigniswere the highest-level.The leaf C,N,P,K,Mg content between the discrete degreewas small,and the content of Ca in lea ves was a large discrete degree.The analysis of leaf nutrient content correlation showed that correlation between leaf Ccontents and leaf Cacontents reached a significant level(P < 0.01),nega tive correlation,leaf N contents and leaf Mg contentswere positively correlated at the 0.01 level,there was a positive correlation between leaf Pcontents and leaf K contents at 0.01 level,there was a significant positive correlation between leaf Ca contents and leaf Mgcontents(P <0.01).The ratio of leaf nutrient elements among different species were different,which the ratio of the leavesN/P,C/P,C/K,N/K Sapium rotundifolium significantly were the highest-level in the round leaves,the ratio of C/N inLiquidambar formosana was the highest-level,the ratio of K/P in Cinnamomum camphora was the highest-level,the ratio of Ca/K and Ca/Mg in Celtis sinensis werethe highest-level,the ratio of K/Mg in Lindera communis was the highest-level.Although the ratio of leaf nutrient elements among different species were different,but the coefficient of variation was small,indicating that these elements on tree growth basically played a synergistic role.There was a significant linear positive correlation between C content and the ratioof C/N in leaves,then,there was a very significant negative linear correlation betweenthe N content and the ratio of C/N of leaves.There were significant positive linear correlation between N content and the ratio ofN/P in leaves,while,the content of the plant leafP andthe ratio of N/P,C/P exist a negativelinear.(4)The content of C,K,Ca and Mg in leaves of different life types were significantly different,the content of C,P,K in evergreen leafwere significantly higher than that of deciduous trees,while the leaf Ca content of deciduous tree species was significantly higher than that of evergreen tree species.Leaf nutrient element ratio,the ratio ofCa/K,Ca/Mg and K/Mg were significantly different between the two groups,the ratio of Ca/K and Ca/Mg in leaves of deciduous tree were significantly higher than those of evergreen tree species while the ratio of K / Mg was significantly lower than that of evergreen tree species.The difference between leaf elements and elementa l ratio of different life tree species shows that the strategy of nutrient adaptation of different life plants is different.(5)The regression analysis showed that the contents of nutrient elements in soil,roots and leaf of forest in the study area showed that: there was a significant positive correlation between root C content and soil Ccontent,and there was a significant negative correlation with soil Ncontent;There was a significant positive correlation between root and soil Pcontent;Root Ca content was negatively correlated with soil N content that was positively correlated with soil Cacontent(P<0.05).Leaf C content was significantly negatively correlated with soil K content.There were significant positive correlation between leaf Ca content and soil Ccontent,K content;there was a significant negative correlation between the content of Mg in the piantleafand the content ofMg in the soil(P <0.05).The C content and P,C,K content showed a significant negative correlation,and N content in the roots was positively correlated.The leaf Ca content and the root C element,K content showed a significant positive correlation,and N content in root was significantly negative correlation(P<0.05).A comprehensive analysis of the nutritional status of "Soil-Root-Leaf" system,the results showed that the nutritional status of Celtis sinensis "Soil-Root-Leaf" system was the best,Zenia insignis times,Liquidambar formosana and Cinnamomum bodinieriare relatively poor,this indicates that there may be nutrient restrictions on the local habitat of Liquidambar formosana and Cinnamomum bodinieri.