Nutrient Resorption Of Plants In Different Habitats Of Desert Ecosystems In Arid Regions

Nutrient resorption is one of the most important survival strategies to deset plants,which is vital to the composition and stability of plant community,and nutrient cycle of ecosystem.Most of the previous studies about nutrient resorption of plants have focused on grassland,forest and field ecosystem,while the studies in the desert ecosystems are still limited.Moreover,no pulications have studied the relationship between nutrient resorption and water use efficiency to date.Exploring the plant nutrient resorption in desert ecosystem will not only benefit to understanding plant nutrient use strategies under abiotic stresses but also provide a basis for plant protection in this area.In order to explore the relationship between nutrient resorption and ecological adaptability of desert plants,we studied the characteristics of water use efficiency and resorption efficiency in the community level and individual level of three key nutrients including nitrogen?N?,phosphorus?P?and potassium?K?.Influence of various factors on the resorption efficiency for C₃ plants in individual level in different habitats such as desert,gravel desert and saline meadow of Minqin County.The main results are shown below:?1?The average resorption efficiency of N,P,K were 57.63%,56.89%and48.73%,all of them were significantly lower than the global averages.The average stable carbon isotope abundance(?¹³C)of C₃ plants was-25.04‰,which were significantly higher than the global averages,while C₄ plants was-14.13‰.It means that harsh conditions have no effects on the nutrient resorption efficiency of plants in desert environments,but enhance their water use efficiency.?2?There were differences in N,P,K resorption efficiency and?¹³C of plant leaves at community level in different habitats.The results of nutrient resorption efficiency for N and P showed:saline meadow>gravel desert>desert,while that of K was:saline meadow>desert>gravel desert.?¹³C:gravel desert>desert>saline meadow,and there is significant difference among three habitats.All sites studied could be divided into saline and non-saline habitats by analysing the soil properties,resorption efficiency of N,P,K and?¹³C in community level.All the above results suggested that the selection and filterability of sepcific habitat for nutrient resorption efficiency and water use efficiency.?3?Nutrient resorption efficiency and?¹³C in different community are determined by the edificator.The result of nutrient resorption efficiency showed that N?64.57%?and K resorption efficiency?53.49%?in Form.Reaumuria songarica were the highest,and the P resorption efficiency in Form.Kalidium foliatum is the highest?53.49%?,while resorption efficiency of P and K in Form.Oxytropis aci-phylla was the lowest.For?¹³C,it was the lowest?-26.49‰?in Form.Reaumurias-ongarica,and highest in Form.Salsola passerina?-20.55‰?.?4?Nutrient resorption efficiency and?¹³C of desert plants in different life forms and functional groups are different.N resorption efficiency:grass>shrub>arbor,C₄plants>C₃ plants.P resorption efficiency:shrub>grass>arbor,C₃ plants>C₄ plants.K resorption efficiency:grass>arbor>shrub,C₄ plants>C₃ plants.?¹³C of leaves:arbor>shrub>grass,C₃ plants>C₄ plants.N,P and K resorption efficiency and?¹³C of non-nitrogen fixing plants were higher than nitrogen fixing plants.?¹³C of C₃ plants in different families are different,Tamarix>Polygonaceae>Polygonaceae>Gramineae>Others.Polygonaceae are higher than Polygonaceae for C₄ plants.?5?Various factors(soil properties,?¹³C,leaf element content and functional traits of plants)affecting nutrient resorption efficiency of C₃ plants with different pathways and degrees.There was no significant correlation between N resorption efficiency and N content and specific leaf area?SLA?in green leaves,N resorption efficiency is positively correlated with?¹³C,soil total nitrogen content,soil water content,pH,soil electric conductivity,soil available phosphorus,and N content in senesced leaves,but negatively correlated with leaf dry matter content?LDMC?.P resorption efficiency had no significant correlation with P content in green leaves and SLA,but positively correlated with?¹³C,and negatively correlated with LDMC.K resorption efficiency and no significant correlation with LDMC,but positively correlated with SLA,and negative correlation with K content and?¹³C in green leaves.Therefore,structural equation model?SEM?analysis indicated that N,P,K concents of plant may be the key factors that directly affected the nutrient resorption efficiency of C₃ plants.