Effects Of Environmental Factors And Phylogeny On Nutrient Resorption In Plant Leaves

Leaf nutrient resorption is an important resource utilization strategy for plants to adapt to the environment.At the same time,this strategy also has important effects for ecosystem carbon and nutrient cycling.It is of great significance to illuminate the general rule of plant nutrient resorption and reveal the factors that control the process of plant nutrient resorption.It is generally considered that there are three strategies for plant control of leaf nutrient reuptake,namely: stoichiometry control strategy,nutrient restriction control strategy,and nutrient concentration control strategy,but the importance of the three varies in different studies,and they are essentially determined by environmental factors such as soil nutrients and temperature.In addition,phylogeny,as a factor that characterizes the similarity between plants theoretically,has an important impact on plant nutrient reuptake,so it has also been regarded as an influencing factor by researchers in recent years and included in the study of leaf nutrient reuptake,but its role is still unclear.This research took woody plants of Cangshan forest ecosystem in Dali,Yunnan as the research object,set up 6 plots on the western slope of Cangshan at an altitude gradient of 200 m,investigated and collected samples of 33 species of woody plant living leaves and fallen leaves in each plot,the content of nitrogen(N),phosphorus(P),calcium(Ca),magnesium(Mg),manganese(Mn)and other nutrients in living leaves and leaf samples were determined,as well as the thickness,area,specific leaf weight and other indicators of living leaves.Analyze soil nutrient content,monitor atmospheric temperature and other environmental factors of the plot.Based on the measurement results of the above indicators,the nutrient resorption efficiency and nutrient resorption proficiency of each species were obtained,and then the altitude pattern of nutrient reabsorption was clarified,and the influence of environmental factors and phylogeny on nutrient resorption was revealed,and the following main results were obtained.(1)Nutrient element concentration was the main factor regulating nutrient reabsorption,and the effects of altitude,soil nutrient content,annual average temperature and functional traits in leaf morphology were not obvious.(2)There was a scale effect on the control factors of nutrient reabsorption,and as the scale of the study gradually expanded from population to community to ecosystem,the influence of nutrient content in green leaves on nutrient reabsorption increased.This result underscores the need to consider the scales studied in the face of the complex relationships between current control factors for nutrient reabsorption.(3)In the history of plant evolution,nitrogen resorption proficiency,calcium reabsorption efficiency and manganese reabsorption efficiency were detected with significant phylogenetic signals,but the others had no significant phylogenetic signals.The effect of phylogeny on nutrient resorption was removed by Phylogenetic Independent Contrasts,and the results before and after evolution were compared,and it was found that phylogeny had no significant effect on leaf nutrient resorption in woody plants in Cangshan mountain.(4)In this paper,the nutrient reabsorption convergence hypothesis is proposed to explain two phenomena related to nutrient reabsorption.First,with the increase of nutrient content in green leaves,the nutrient reabsorption efficiency increases,while the nutrient reabsorption decreases.Second,for elements with strong mobility(such as N and P),the correlation between the content of nutrients in green leaves and their nutrient reabsorption efficiency is more significant,and the correlation with reabsorption is weaker,and for elements with weak mobility,the content of nutrients in green leaves is weaker in correlation with their nutrient reabsorption efficiency,and the correlation with nutrient reabsorption is stronger.This hypothesis provides a theoretical explanation for our understanding of the relationship between nutrient uptake intensity and nutrient content in green leaves,and the relationship between Nu RE and Nu RP and control factors.