Spatial Variation Patterns Of Nutrient Element Concentrations In Two Sympatric Pine Trees

The concentrations of plant nutrient elements reflect the dynamic balance of plant growth characteristics and environmental responses.However,researches on the geographical and elevation variations of pine nutrient elements and their responses to the environment have not been in-depth.Pinus hwangshanensis and Pinus massoniana are both endemic species in China and important afforestation species in barren mountains.They are closely related,occupy different altitude ecological niche,and have natural hybrid domains in the vertical transition zone.This study determined the concentration of carbon(C),nitrogen(N),phosphorus(P),calcium(Ca),magnesium(Mg)of P.hwangshanensis and P.massoniana at different elevations in five sites,including Mt.Sanqingshan,Mt.Lushan,Mt.Jinggangshan,Mt.Huangshan and Mt.Tianmushan.We are committed to revealing the spatial variation patterns of two pine trees and studying their response to environmental changes through one-way ANOVA,correlation analysis,nested analysis,and multiple regression analysis methods.The main findings were as follows:(1)The concentrations of C and Mg in P.hwangshanensis and P.massoniana were significantly different,and the ecological stoichiometric characteristics of P.hwangshanensis were slightly lower than those of P.massoniana.The average concentration(mg/g)of each element in P.hwangshanensis were: C,521.92;N,15.78;P,0.97;Ca,3.13;Mg,0.86.For P.massoniana,the average concentration(mg/g)of each element were: C,537.99;N,16.27;P,0.97;Ca,3.80;Mg,1.17.The plasticity level and the coefficient of variation of C were low,while those of Ca and Mg were relatively high.(2)In general,there were significant differences in nutrient element concentrations among different populations of the two pines.For P.hwangshanensis,the average concentrations(mg/g)of C,N,P,Ca and Mg in different populations were as follows: Mt.Sanqingshan,503.98,16.56,1.01,2.97 and 0.87;Mt.Lushan,529.39,15.66,1.00,3.11 and 1.00;Mt.Jinggangshan,547.43,15.50,0.91,2.85 and 1.09;Mt.Huangshan,520.89,13.67,0.83,3.78 and 0.67;Mt.Tianmushan,499.95,17.40,1.12,3.42 and 0.84.For P.massoniana,the average concentrations(mg/g)of C,N,P,Ca,and Mg in different populations were as follows: Mt.Sanqingshan,541.81,16.87,0.88,5.62 and 1.13;Mt.Lushan,536.62,15.30,0.95,2.59 and 1.07;Mt.Jinggangshan,533.79,15.94,1.07,4.01 and 1.41;Mt.Huangshan,553.26,15.20,0.76,4.00 and 0.92;Mt.Tianmushan,529.72,18.25,1.15,3.39 and1.32.For both trees,the maximum value of N and P concentrations of two pine trees were in Mt.Tianmushan,and the minimum value were in Mt.Huangshan.The maximum value of Mg concentration was in Mt.Jinggangshan,and the minimum value was in Mt.Huangshan.The main source of variation in ecological stoichiometric characteristics was intra-population variation,and inter population variation was lower than intra population variation.Elevation accounted for the largest proportion of Ca concentration variation with 0.567,while species accounted for 0.258 in Mg concentration variation.(3)Through regression analysis,it was found that different stoichiometric characteristics of two pine trees had different responses to the environment.For P.hwangshanensis,C concentration was affected by latitude;N concentration was affected by elevation;P concentration was affected by elevation,latitude,and mean annual precipitation;there was no significant relationship between Ca concentration and various environmental factors;Mg concentation was influenced by elevation,latitude,and mean annual temperature;C: N was affected by elevation;C: P was affected by elevation,latitude,and mean annual precipitation;N:P was affected by elevation and longitude;Ca: Mg was influenced by elevation and latitude.For P.massoniana,there was no significant relationship between C concentration and various environmental factors;N concentration was influenced by longitude and mean annual precipitation;P concentration was influenced by latitude and mean annual temperature;Ca concentration was influenced by longitude and mean annual temperature;Mg concentration was influenced by longitude and mean annual precipitation;C: N was affected by longitude and mean annual precipitation;C: P was affected by longitude;N: P was affected by longitude;Ca: Mg was influenced by longitude and mean annual precipitation.Most ecological stoichiometric characteristics of P.hwangshanensis were driven by elevation factor and had a certain elevation distribution pattern;Most ecological stoichiometric characteristics of P.massoniana,were driven by longitude factor and had a certain longitude distribution pattern.In conclusion,there were significant differences in element concentrations in the needles of P.hwangshanensis and P.massoniana among populations,and different stoichiometric characteristics of the two pine trees had different responses to the environment.Studying the variation of ecological stoichiometric characteristics of P.hwangshanensis and P.massoniana was helpful to understand the utilization strategies of nutrient elements,provided a basis for studying the ecological adaptation strategies of pine trees to barren environments and the characteristics of pioneer tree species,and was of great significance for natural forest protection and adaptive management.This study did not explore the response to soil factors,and the distribution of sampling points was not widespread enough.Further researches are needed in the future.