Study On The Physiological And Ecological Adaptation Of Phyllostachys Glauca In Limestone Mountain

Native plants in karst have a natural adaptation strategy to the lack of soil moisture and available phosphorus（P）.In recent years,studies of karst plants has been focused on plant adaptability to drought,but the adaptation of low P is lack of research and the mechanism is unclear.Moreover,there are a lot of studies concentrating on root while less attention was paid on leaves,and it indicated that the current research perspective on organ is too narrow and restricted.However,leaves play an important role in acquiring resources and they are sensitive to changes of environment,therefore leaf functional traits and nutrient utilization provides clues of plant adaptation strategies.In this study,dominant species（Phyllostachys glauca）grown in limestone mountain of northwest Jiangxi Province were selected as subjects.Taking Ph.heteroclada,Camellia oleifera,Lindera glauca and Quercus fabri in limestone habitat,and Ph.glauca in non-limestone habitat as a control,we compared and analyzed leaf functional traits,nutrient and P allocation of different species through fixed-point observation and experimental methods.The main results are as follows:（1）In leaf structural traits,leaf dry matter content（LDMC）of evergreen broad-leaved plants（C.oleifera）was significantly lower than other species（p<0.05）,leaf thickness（LT）,leaf mass per area（LMA）and leaf longevity（LL）of C.oleifera were significantly higher than other species（p<0.05）.In leaf physiological traits,water-use efficiency（WUE）of Ph.glauca was significantly higher than other species（p<0.05）,Q.fabri had the highest net photosynthetic rate（P_n）and transpiration rate（Tr）,and the lowest WUE.In leaf nutrient traits,leaf nutrient concentration of bamboo species was high,and mature leaf total P concentration（MLP）of Ph.glauca(0.983 mg·g^-1)was the highest,and N:P of all species was higher than 22.Different species had distinct differences according to leaf functional traits.Distinguish plants from resources invested in leaf structural traits（LL,LMA）,P_nand nutrient concentration.C.oleifera was a typical"slow investment-income"species,bamboo species and deciduous broad-leaved plants belonged to"rapid investment-income"type,all the types made trade-offs between long LL,low P_nand short LL,high P_n,respectively,to adapt to habitat.（2）Different species in the limestone mountains adopted different strategies for nutrient utilization.In terms of nutrient resorption efficiency,P resorption efficiency（PRE）of senescent leaves by all species was generally higher than that of nitrogen resorption efficiency（NRE）.Nutrient resorption efficiency of bamboo species was higher than that of other species,of which PRE of Ph.glauca was 79.3%.The NRE and PRE of C.oleifera was only about 20%,which indicated a phenomenon of"luxury consumption".Deciduous plants had higher photosynthetic nutrient use efficiency,photosynthetic N-use efficiency（PNUE）and photosynthetic P-use efficiency（PPUE）of Q.fabri was 117.73μmol·mol^-1·s^-1and6922.87μmol·mol^-1·s^-1,which was about twice of PNUE and PPUE of C.oleifera.Based on LL and photosynthetic nutrient use efficiency,the nutrient use efficiency of leaf survival period was obtianed,leaf N use efficiency（LNUE）and leaf P use efficiency（LPUE）of C.oleifera was 3434.34 mol·g^-1and 192149.28 mol·g^-1.Bamboo species,especially Ph.glauca kept maintaining high leaf nutrient use efficiency.（3）The concentration and allocation of leaf P fractions were an important strategies for plants to adapt to P-limited habitats.Distinguish species by the concentration and allocation of inorganic P（Pi）and residual P（RP）,one is bamboo species with high Pi and strong physiological metabolism,concentration(0.297 mg·g^-1)and proportion（33.18%）of Pi in the leaves of Ph.glauca were the highest,while concentration(<0.020 mg·g^-1)and proportion（<2%）of RP were lower;the other is broad-leaved plants with low Pi and relatively weak physiological metabolism,concentration of P fractions of C.oleifera were the lowest,while proportion of other P fractions were higher except for RP and Pi.Nucleic acid P（NP）and lipid P（LP）of deciduous plants were relatively high,but the concentration(0.45 mg·g^-1)and the proportion（>6%）of RP were the highest.（4）There were no significant differences in the leaf functional traits,nutrient use efficiency and P fractions allocation of Ph.glauca in different habitats.In leaf functional traits,Ph.glauca in non-limestone habitat（CK Ph.glauca）had higher WUE;The N use efficiency of Ph.glauca was significantly higher than that of CK Ph.glauca（p<0.05）.In conclusion,native plants in limestone mountains have different physiological and ecological adaptation strategies:C.oleifera belonged to the"slow investment-income"species,with low P_n,long leaf longevity and total nutrient utilization due to high leaf survival time.Bamboo species and deciduous plants belonged to the"rapid investment-income"type.Bamboo species had high P_n and high nutrient resorption efficiency,and deciduous plants had high P_n to maintain high photosynthetic nutrient use efficiency.High WUE,P acquisition and use ability,concentration and proportion of Pi are important physiological and ecological adaptation strategies for Ph.glauca to be the dominant species in limestone mountain.This study explained the adaptation strategies of different species to resource-poor habitats through leaf functional traits and nutrient utilization.Combined the allocation of P fractions with leaf functional traits and nutrient utilization,the mechanism of adaptation of different species in P-limited habitats were interpreted.Based on the revealed physiological basis of strong adaptability of the dominant species Ph.glauca,we provided scientific basis for vegetation selection and ecological restoration in karst areas.