Distribution Pattern And Influencing Factors Of Total Phosphorus In Natural Forests And Plantation Forests In China

Phosphorus（P）is one of the most important elements required for plant growth and development in forest ecosystems,and plays a vital role in soil quality and plant productivity.Soil P availability often limits plant productivity.Classical theories suggest that total P content declines at the temporal scale of pedogenesis,and ecosystems develop toward the efficient use of scarce P during succession.However,the trajectory of ecosystem P within shorter time scales of succession remains unclear.Previous studies of P cycling have focused mainly on larger scale or single type forest ecosystems at the regional scale,lacking information on the influence of forest origins on a large scale,which may help explain why there is still uncertainty about this topic in research to date.The study takes soil total P and vegetation P as the research topics between natural forests（NF）and plantation forests（PL）in China’s forest ecosystems,based on the forest ecosystem survey data of total P in the subject of"China’s forest ecosystems carbon sequestration status,rate,mechanism and potential"（XDA05050200）,combined with high–resolution climate data extracted from terrestrial surface area with spatial coordinates.Based on the comprehensive consideration of climate,vegetation type,vegetation biomass,species richness,and stoichiometry,the distribution pattern of phosphorus in two kinds of forest origin forest and its changes with succession/growth stage were analyzed.From the scale of the ecosystem,the differences in changes in P levels over time of two kinds of forest origin stand were compared,and the factors affecting the difference between NF and PL were explored.Our research aims to provide some data support and a theoretical basis for forest management,and it is also expected to help to improve local biogeochemical models.The main research results are summarized as follows:（1）On the national scale,soil total P content(0.51 g·kg^-1)and vegetation P content in NF(tree layer 0.88 g·kg^-1,shrub layer 1.15 g·kg^-1,herb layer 1.35 g·kg^-1,litter 0.97 g·kg^-1)were significantly higher than those in PL(soil 0.47 g·kg^-1,tree layer 0.75 g·kg^-1,shrub layer 0.95 g·kg^-1,herb layer 1.18 g·kg^-1,litter 0.80 g·kg^-1)（p<0.05）.With the change of succession/growth stage,NF and PL showed two opposite states.The soil total P content and each vegetation layer’s P content in NF increased significantly（p<0.05）,while those of PL decreased significantly（p<0.05）.This indicated that compared with PL,NF have a more effective mechanism for retaining P,while the PL was consuming P all the time.（2）On the regional scale,we studied NF and PL in different climatic vegetation areas,especially in typical"P deficiency"areas such as southern tropics and subtropics regions,found that soil total P content in northern temperate and warm temperate vegetation areas was significantly higher than that in southern tropical and subtropical vegetation areas（p<0.05）,but there was no significant difference in vegetation P content between NF and PL in southern tropical and subtropical ares.However,with the change of succession/growth stage,the trends of soil P content of NF and PL still conforms to the variation law at the large-scale change.Even in typical"P deficiency"areas,NF can still effectively accumulate P in soil.（3）In terms of spatial distribution,there was no significant difference in the trend of soil P content between NF and PL with latitude and altitude changes.With the succession/growth progressed,there was no significant difference in soil total P content between NF and PL with the changes of longitude,latitude,and altitude.In the later stage（LS）of succession/growth,the P content of each vegetation layer in NF decreased with the increase of longitude,while that in PL increased significantly with the increase of longitude（p<0.05）.（4）Through the analysis of different climates and site conditions,it was found that the soil P contents and vegetation P contents of NF and PL decreased significantly with the increase of mean annual temperature（MAT）and mean annual precipitation（MAP）.There was no significant difference in the response to temperature and precipitation in different succession/growth stages,indicating that climatic factors were not the main reason for the difference in P content between NF and PL.（5）There were significant differences in the underground（root）biomass changes between NF and PL.With the progression of succession/growth,the tree layer biomass of both NF and PL was significantly increased（p<0.05）,and the root biomass of NF was also significantly increased at LS（p<0.05）.This may prove that higher plant diversity with deeper roots and more soil animals（e.g.,invertebrates）to capture and exploit P from deeper soil,as well as a more complex canopy structure enabling vegetation to retain P via re-sorption at leaf senescence and to recycle P via organic matter decomposition,contribute to the differences observed between NF and PL.（6）The P status of NF and PL was different under different vegetation types.Compared to deciduous forests,evergreen forests have lower soil total P content,and vegetation P contents were significantly lower than that of other vegetation types.Evergreen tree species can reduce the P content of leaves before leaf shedding through the transfer mechanism,making them more adapted to low P environments.Compared to broadleaf forests and mixed forests,coniferous forests had higher soil and vegetation P content,mainly due to different tree species nutrient recycling efficiencies,and NF have significantly higher species richness than PL（p<0.05）,which is more conducive to forming a more stable community structure.With the change of succession/growth stage,the species richness of PL increased at LS,while the dominant richness did not change significantly,which may lead to a decrease in litter P content and affect the soil P content.（7）With succession/growth progressed,the root N:P ratio of PL increased significantly,while that of NF decreased,indicated that P gradually became a limiting factor for the growth of PL,while NF could effectively alleviate the limitation of P with the succession.Our results indicate that increasing P demand of natural vegetation during succession,may raise,retain,and accumulate P from deeper soil layers.In contrast,ecosystem P in PL was depleted by the more rapidly increasing demand outpacing the development of a P-efficient system.We advocate for more studies to illuminate the mechanisms for determining the divergent changes,which would improve forest management and avoid the vast degradation of PL ecosystems suffering from the ongoing depletion of P.