| Phosphorus is an essential element in the process of plant growth and development,and is closely related to growth and metabolism.The current shortage of phosphorus resources and the limitation of soil phosphorus are hot spots of global concern.The distribution ratio and migration and recovery efficiency of different phosphorus components in plants can affect many physiological processes including plant photosynthesis and metabolism,and the absorption and utilization efficiency of phosphorus by different tree species are very different.In this study,samples of leaves,litter leaves and branches(divided into three levels according to the river system classification)of 18 common subtropical tree species(divided into conifers,deciduous broad-leaved trees and evergreen broad-leaved trees)were collected,using the latest 31P NMR method Determine the content of phosphorus components(orthophosphate.phosphate monoester,phosphate diester and pyrophosphate)in various parts of different tree species,and determine the nutrient content and morphological characteristics,and compare the leaf phosphorus content and nutrient recovery of different functional types of subtropical tree species Efficiency,discuss the functional traits of different tree species and the relationship with phosphorus,and provide a scientific basis for the conversion,release,turnover and sustainable development of phosphorus in subtropical forests.The main findings are as follows:(1)There are differences in leaf traits between different functional types of tree species,among which the leaf area and aspect ratio of coniferous species are significantly different from those of deciduous broad-leaved and evergreen broad-leaved species.The tissue density of the branches of different functional types of trees all showed a trend of increasing from the first-level to the third-level branches,and the tissue density of the branches of each level was the same among the different functional types of trees.This study found that different functional types of tree species have a significant impact on the content of C,N,TP and the stoichiometric ratio,but the different parts of the tree did not show a significant impact on the C content,and the interaction berween the two is only for N and C:N Have a significant impact.The contents of nitrogen and total phosphorus from leaves to branches of different types of trees showed a downward trend.The difference in total phosphorus content in leaves of different functional types of plants is that deciduous broad-leaved species are larger than coniferous species and greater than evergreen broad-leaved species.In this study,the evergreen and deciduous broad-leaved species are mainly limited by phosphorus,and coniferous species are limited by nitrogen and phosphorus.(2)There are differences in the content of various phosphorus components in the leaves of different tree species.Among them,the content of pyrophosphate in the leaves of different tree species has the largest difference.The highest content of Sassafras tzumu is 33.58 mg/kg,and the lowest is 0.269 mg/kg of Schima superba.Different functional types of tree species and different parts have significant effects on the phosphorus content.The phosphorus content of different functional types of trees basically shows a downward trend in each level from leaf to branch.Due to the different distribution of phosphorus components in different functional types of trees,the content of each phosphorus component in leaves is inconsistent among different functional types of trees.By analyzing the distribution ratio of the phosphorus components in the extractable liquid total phosphorus,it is found that the distribution ratios of the phosphorus components in each part of different functional types of tree species are different.Among them,orthophosphate has the highest proportion,followed by phosphoric acid monoester,then phosphoric acid diester,and pyrophosphate has the lowest.The proportion of orthophosphate in leaves of coniferous species is 43%,that of deciduous broad-leaved trees is 61%,and that of evergreen broad-leaved trees is 55%.The proportion of orthophosphate in each grade of branches is about 70%higher than that of leaves,indicating that phosphorus may migrate between different parts in the form of orthophosphate.It is worth noting that the content of pyrophosphate in the leaf litter of each functional type of tree species is higher than that in the leaf,indicating that during the nutrient recovery,not only the pyrophosphate is not recovered,but also other phosphorus components are converted into The case of pyrophosphate.In different tree species,only the content of orthophosphate and phosphate monoester have a very significant positive correlation with the content of extractable total phosphorus.The reason may be related to the extraction rate of total phosphorus in the NaOH-EDTA extract in this study.The phosphorus group in plants There are mainly two kinds of orthophosphate and phosphate monoester.Because the extraction rate is not optimal,some phosphorus components such as phosphate diester may not be sufficiently extracted.Leaf aspect ratios in different tree species showed significant phylogenetic signals,while other traits did not show phylogenetic signals.(3)This study found that nutrient recovery efficiency varies greatly among different tree species,ranging from 5%to 71%.Among them,the nitrogen and phosphorus recovery efficiencies of evergreen broad-leaved trees are 19.96%and 38.82%,deciduous broad-leaved trees are 21.29%,34.10%,and the nitrogen and phosphorus recovery efficiencies of coniferous trees are 66.82%and 49.85%.Coniferous trees have higher recovery efficiency than broad-leaved trees.The recovery rate of nitrogen and phosphorus.Due to the extremely low soil available phosphorus content in subtropical regions,the phosphorus recovery efficiency of all functional types of tree species is higher than the nitrogen recovery efficiency.The recovery efficiency of orthophosphate and phosphodiester in different functional types of trees is relatively high,while the recovery efficiency of phosphate monoesters is low,and the recovery of pyrophosphate of each functional type of tree species is negative.The correlation analysis shows that there is a significant correlation between nitrogen recovery efficiency and specific leaf area and specific leaf weight,and there is a significant correlation between orthophosphate recovery efficiency and leaf area.(4)This study found that the content of orthophosphate has a significant correlation with leaf traits,the content of phosphate monoester has a significant correlation with the aspect ratio,the specific leaf area and the specific leaf weight,and the pyrophosphate content has a significant correlation with the specific leaf area.Significantly positive correlation.However,there is no significant correlation between the phosphodiester and the leaf traits,which may be related to the extraction effect of the phosphodiester.The leaf traits of different tree species are related to each other,and there is a significant correlation. |
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