Comparison Of Foliar Element Concentrations Of Plants From Typical Habitats In Southern China

Karst forests,mangroves and evergreen broad-leaved forests grow on different typical habitats in southern China.Due to the strong differeces in rock substrate,soil and other environmental factors,plants from these habitats could show different nutrient limitation,mineral element accumulation and stoichiometric characteristics as an adaptation to the environmen.In this study,the leaf element concentrations and stoichiometrial characteristics of tropical karst forests(Xishuangbanna,Yunnan,and Nonggang,Guangxi),a tropical mangrove forest(Wenchang,Hainan),and a subtropical evergreen broad-leaved forest(Nanling,Guangdong)from the literature,in southern China,were compared and analyzed in order to explore the plant adaptation to the different habitats.The results showed that:(1)The foliar composition of mineral elements differed among these habitats.In Xishuangbanna karst forest,the concentration of leaf elements from high to low was ranked as Ca>N>K>Mg>P>Fe>Mn>Na>B>Zn.In Nonggang karst forest,the concentration of the leaf elements from high to low was Ca>N>K>Mg>S>P>Fe>Zn>Cu.The element composition of both karst forests was Ca>N>K>Mg,showed the characteristics of rich in Ca、Mg.In mangroves,the concentration of leaf elements from high to low was N>Na>K>Ca>Mg>S>P>Si>Fe>Mn>Zn.The element characteristics was N>Na>K>Ca,showed high foliar accumulation of Na.(2)The concentrations of leaf elements were different in different typical habitats.Leaf N concentrations of the karst plants were significantly higher than that of the evergreen broad-leaved forest.The foliar P concentrations of the karst and mangrove plants were significantly higher than those of the evergreen broad-leaved forest plants.K concentration differed significantly between the two karst habitat plants.Ca of karst plants was significantly higher than that of mangrove and evergreen broad-leaved forests.Leaf Mg was significantly higher in Nonggang than in Xishuangbanna karst plants.Wheras,Foliar Fe of Xishuangbanna karst plants was significantly higher than Nonggang karst plants and mangroves.The evergreen broad-leaved forest on acidic soil had significantly higher foliar Mn than other habitats.Foliar Na of mangrove plants in the saline environment was significantly higher than the other habitats.Leaf Zn of Nonggang plants was significantly higher than that of plants in other habitats,and their S was significantly lower than that of mangroves.(3)The plants from the different habitats showed different enrichments and deficiency in mineral elements.Karst forests were enriched with Ca and Mg,while plants in Nonggang area contained higher Mg.The karst plants in Xishuangbanna were deficit of K,Fe,and Zn.Nonggang karst plants had higher leaf K,Zn and S concentrations.The karst forest plants may be restricted by N and P,but mainly by P.Mangrove plants were enriched with P,Ca,Mg,Na and S elements,especially Na accumulation in leaves.However,mangrove plants showed deficits of Fe,Si and Zn.Mangrove plants were limited of N.Because of acid soil,the plants in subtropical evergreen broad-leaved forest had a relatively high foliar Mn accumulation but low P concentrations.(4)The concentrations of N,P and S elements in leaves of plant species at the top of karst hills were significantly lower than those at the slope and valley in the Nonggang karst area.The concentrations of K,Ca and Mg in leaves of plant species at the valley were the lowest and significantly lower than those at the peak.Fe and Zn were the highest at the valley and the lowest at the peak.The changed of soil thickness and p H along the valley-slope-peak continuum may be an important reason for the difference in foliar nutrient concentrations inthe plants in different karst microsites along the topography.(5)The stoichiometry relationship of elements changed in plants from different typical habitats.In studied plants from the different habitats,there was a significant positive correlation between foliar N and P concentrations,and this stable synergistic relationship was a general rule for plants.The two divalent cationic elements Ca and Mg have synergistic relationship in karst forests and evergreen broad-leaved forest,but not in the mangrove forest.N and K were synergistic in mangroves and plants of the evergreen broad-leaved forest,but no synergistic relationship between N and K in the karst plants.P and Zn showed synergistic relationship in both karst plants and mangroves.The mangrove plants showed antagonistic relationship between K and Mn,but there was no correlation between K and Mn in plants of the karst forests and evergreen broad-leaved forest.S and P elements showed positive correlation in plants of the Nonggang karst forest,but there was no correlation between these two elements in mangrove plants,which all had high P.The present results have important implications for the understanding and modelling of biogeochemical cycle and management of forest ecosystems.