Nutrient limitation and resorption characteristics of different aged Schima superba plantations in central subtropical China
Nitrogen(N)and phosphorus(P)resorption is a key nutrient use strategy for trees to cope with nutrient limitation and improve nutrient use efficiency.The variation and mechanism of N and P resorption of trees with stand development are still unclear.In this study,we measured N and P concentrations of fresh and senescent leav-es of Schima superba across different stand ages(6,18,26 and 34 years old)in Nanping,Fujian Province,and calculated nutrient resorption efficiency.Combining with the concentrations of soil total N(STN),total P(STP),ammonium N,nitrate N and available P(AP),we further explored the regulation mechanism of nutrient resorption in S.superba leaves across different stand ages.The results showed that STN and STP concentrations changed signi-ficantly with increasing stand age.The STP concentration of 6-year-old plantation was significantly higher than that of 26-and 34-year-old plantations.The STN concentration of 26-year-old plantation was significantly higher than that of 6-,18-and 34-year-old plantations.With increasing stand age,TN concentration of fresh leaves in 34-year-old S.superba was significantly higher than that of 6-,18-and 26-year-old S.superba.There was no significant difference in TP concentration of fresh leaves,TN and TP concentrations of senescent leaves in different stand ages(P＞0.05).Leaf N resorption efficiency(RN)increased with increasing stand age,ranging from 35.48％to 44.52％,with an average of 38.25％.Leaf P resorption efficiency(RP)decreased with increasing stand age,ran-ging from 30.99％to 53.50％,with an average of 40.42％.The relative resorption efficiency of N and P(RN∶Rp)of 6-and 18-year-old S.superba was less than 1,and that of 26-and 34-year-old S.superba was greater than 1.Fo-liar P and N concentrations of the four stands were less than 1 and 20 g·kg-1,respectively.The N/P in fresh lea-ves increased significantly with increasing stand age,ranging from 17.62-24.40 and greater than 16,indicating that the growth of S.superba was limited by P.Leaf RN was positively correlated with soil ammonium N,nitrate N and STN/STP ratio.Leaf Rp was positively correlated with soil available P concentration and negatively correlated with ammonium N(P＜0.05).RN∶Rp was significantly positively correlated with STN/STP ratio(P＜0.05),indicating a positive feedback mechanism between soil nutrient concentration and nutrient resorption.Our results showed that leaf RN increased to meet the N demand with the development of S.superba plantation.However,leaf Rp decreased,resulting in increased P limitation.It is indicated that P resorption may not be the dominant mechanism underlying its adaptation to P limitation.Other ways of S.superba to cope with P limitation,as well as the interaction mecha-nism of P resorption with changes in soil ammonium N concentration should be further studied.
万方数据
维普
