The Correlationship Between Plant Foliar Phosphorus Fractions And Soil Nutrients

Phosphorus is a crucial and essential element for plant's development,it is evolved in almost all of the phyisiological processes in plant and plays significant role.However,the whole globe is confronted with a growing shortage of phosphorus resources,and a significant proportion of soil is suffering various phosphorus restriction simultaneously in terrestrial ecosystems.There are great differences in plants of their efficiency of absorption and utilization of phosphorus.Numerous previous researches of plant phosphorus mainly focus on the two parts of inorganic and organic phosphorus.However,along with the intensive study of plant-soil relations,it is found that there are obviously differences in the distribution of phosphorus in plants.The different phosphorus fractions in plant leaves not only perform respective functions,but also redulate lots of physiological processes including plant photosynthesis and metabolism.Therefore,it is vitally necessary and important to excavate the relationship between different plant phosphorus fractions(inorganic phosphorus,nucleic acid phosphorus,lipid phosphorus,metabolic phosphorus and residual phosphorus)and soil nutrients.In this study,the natural ecosystem of Jurein Bay in southwestern Australia,and the artificial forest ecosystem in southwestern China are the objects,we investigated different patterns of plant leaf P distributions and their responses to soil nutrients(mainly were soil total P,total N and resin P)in different ages of dunes(from 6500 years old to two million years old),and also the relationship between plant phosphorus fractions and soil nutrients(soil total P,total N and resin P and so on)in afforestration species(P.massoniana and C.hystrix)of different leaf ages,plant functional groups and plant communities in the artificial forest ecosystem were explored.The main results presented as follow:(1)In different soil chronosequence,the concentrtaion of total nitrogen in the three plants species leaves did not change significantly,but the total leaf phosphorus concentration showed significantly different changes.Acacia rostellifera's total leaf phosphorus concentration was consistent and high in different soils.Melaleuca systena's total leaf phosphorus concentration was higher in young soils,but decreased by 70%as the soil age increased.Hakea prostrata's total leaf phosphorus concentration was significantly lower than that in the other two species,although its total phosphorus concentration of the leaves also showed a significant downward trend with the soil age increasing,while which was different with Melaleuca Systena.Under different soil conditions,there was no significant change in the leaf phosphorus fractions of Acacia rostellifera;the concentration of Melaleuca systena's leaf phosphorus varied with the increased age of the soil,Melaleuca systena allocated nearly 40%of the leaf phosphorus to inorganic phosphorus pool in the youngest soil,while its nucleic acid phosphorus and lipid phosphorus were about 25%respectively.With the increase of soil age,Melaleuca systena's distribution of inorganic phosphorus,nucleic acid phosphosphos and lipid phosphorus all showed a downward trend,while leaf metabolic phosphorus remained relatively similar in all soil chronosequences.Hakea prostrata distributed its leaf metabolic phosphorus and residual phosphorus with similar trends of Melaleuca systena at soil stage 2.At the same time,Hakea prostrata had very low leaf lipid phosphorus concentrtaion at soil stage 2,equivalent to only 1/3 of that in Melaleuca systena and 1/2 in Acacia rostellifera.The relationships between leaf P and soil nutrients also showed significantly differences in three plant species among soil ages.Melaleuca systena had the strongest correlation between soil pH and total leaf phosphorus concentration(R~2=0.45);while the strongest correlation between the soil total phosphorus concentration and the total leaf phosphorus concentration was occurred in Hakea prostrata(R~2=0.51);there was no significant correlation between the total leaf phosphorus concentration and the soil parameters of Acacia rostellifera.There was no correlation between the leaf phosphorus concentration and the total soil nitrogen concentration in all the plant species.With the increasing soil P limitation,H.prostrata and M.systena down regulated their demands for phosphorus,furthermore,they had the capacities to redistribute leaf phosphate,phospholipids and nucleic acids P flexibly,to adapt the environmental stress better.However,A.rostellifera always required plenty of P,and it didn't get a similar ability to redistribute the leaf P fractions,this could be one of the important reasons that A.rostellifera could not spread in serious P deficiency environments.Our results proved that the response to soil nutrients in different plant species could be reflected in their distribution of leaf phosphorus fractions,and the way of these distributions presented different capacities to fit environments.(2)The traits of leaf P fractions and their distribution patters showed significant differences in target afforestation species of China.The total nitrogen concentrations of Pinus massoniana and Castanopsis hystrix in the mixed plantation did not change with the stage of leaf development,but there was difference of that in the Pinus massoniana in monoculture Pinus massoniana plantation.There was no difference in the total leaf phosphorus concentration of mature leaves in Pinus massoniana no matter in the monoculture plantation or in the mixed broadleaf-conifer plantation,but the leaf phosphorus resorption efficiency of Pinus massoniana in monoculture plantation was significantly higher than that of in mixed broadleaf-conifer plantation.In this study,we found both Pinus massoniana and Castanopsis hystrix distributed most of their leaf phosphorus to lipid phosphorus,but Pinus massoniana and Castanopsis hystrix showed significant differences of that in their different leaf stages.The nucleic acid phosphorus concentration of Pinus massoniana in both two plantations decreased significantly with the aging of the leaves,but the nucleic acid phosphorus of Castanopsis hystrix did not change with the aging of the leaves.Secondly,the phosphorus resorption efficiency of P.massoniana was significantly higher than that of the Castanopsis hystrix.Pinus massoniana resorbed its leaf phosphorus from all the phosphorus fractions comprehensively,but Castanopsis hystrix resored its leaf phosphorus mainly from the pools of lipid phosphorus and metabolic phosphorus.The higher leaf N:P ratio of Castanopsis hystrix indicated that it was confronted with a deeper phosphorus limitation than Pinus massoniana.(3)The traits of leaf P fractions in different dominant understory plant species,plant functional groups and plant communities showed significance.The demand for nitrogen and phosphorus in herbaceous plants was higher than that of other plant functional groups,and more leaf phosphorus of herbs was distributed to inorganic and nucleic acid phosphorus pools,It is speculated that the high phosphorus demand for herbs was an important reason to limit its adaptability.There was no significant difference in phosphorus fraction characteristics of the dominant understory species that common occurred in both two plantations,but there was a significant difference in phosphorus fraction characteristics of the dominant understory species that occurred uniquely in the monoculture plantation or in the mixed broadleaf-conifer plantation.In this study,the relationship between the leave phosphorus and the total soil phosphorus was stronger in fern than that of other functional groups,but it is interesting that the leaf phosphorus concentration and the resin phosphorus in the soil of fern was not correspondingly correlated.It is speculated that ferns can get and utilize soil Al-P more effectively than other functional groups by remobilizating it.The concentrations of total leaf phosphorus and total leaf nitrogen and leaf phosphorus fraction of herbs were higher than those of other plant functional groups.(4)The nutrients concentration of the bulk soil in the monoculture P.massoniana plantation and in the mixed broadleaf-conifer plantation did not show a significant difference,except that the soil total nitrogen concentration in the mixed broadleaf-conifer plantation was significantly higher than that of the monoculture P.massoniana plantation.And the nutrients concentration of rhizosphere soil was much lower than that of bulk soil.The plant-available nutrients of the rhizosphere soil in the monoculture P.massoniana plantation were higher than those of the mixed broadleaf-conifer plantation.There was no difference in the concentration of rhizosphere soil resin P of Pinus massoniana and Castanopsis hystrix in two plantations,but the rhizosphere soil Al-P and Fe-P concentrations of the monoculture P.massoniana plantation were significantly higher than that of Pinus massoniana in the mixed broadleaf-conifer plantation.There was no difference in the concentration of rhizosphere soil nitrogen whether it was Pinus massoniana or Castanopsis hystrix.Pinus massoniana mainly used Al-P in the monoculture P.massoniana plantation,while Pinus massoniana and Castanopsis hystrix utilized Al-P,Fe-P and Ca-P in different degrees.The rhizosphere soil of herb plants had more plant-available nutrients than shrubs and tree species.Most of the previous studies of plant leaf P focused on Pi and Po,this study investigated the plant leaf P with five fractions like Pi,lipid P,nucleic acid P,metabolic P and residual P.We compared the differences not only in natural ecosystem but also in artificial forest ecosystem for the plant leaf P and their distributions under different soil nutrients.This study proved that plant distributed their leaf P fractions differently in species,and these kinds of different pattern is tightly linked with their adaptation to environment.Further reseraches of plant leaf P fractions would provide more valuable information to improve the plant's phosphorus-use efficiency,especially for the economical crop species.