Study On Fine Root Characters Of Evergreen And Deciduous Tree Species With Different Root Order In Jiangxi Evergreen Broad-leaved Forest

Plant root is the main functional organ for trees to absorb water and nutrients.It plays an important role in the material cycle and energy flow of forest ecosystem.The aboveground part of deciduous tree species adopts efficient ecological strategy,while evergreen tree species adopts relatively conservative strategy,but little is known about the overall resource strategy of underground fine roots of evergreen and deciduous tree species.In addition,the leaf economic spectrum has been confirmed,but the root economic spectrum has not reached a consistent conclusion.In this study,we selected the first four fine roots of 59 evergreen and deciduous tree species in the subtropics as the research object.By measuring the nutrient,morphological and anatomical properties of the first four fine roots and the nutrient and stoichiometric ratio of carbon,nitrogen,phosphorus and stoichiometry in rhizosphere soil,the differences of fine root characters between evergreen and deciduous tree species and their changes with root order were analyzed,and the ecological strategies of underground fine roots of evergreen and deciduous tree species were explored.The relationship between fine root traits was comprehensively analysed to explore whether the root economic spectrum exists in the fine roots of subtropical woody plants.The main results are as follows: 1.The contents of N and P in fine roots of evergreen species were significantly lower than those of deciduous species(P < 0.05),while the contents of C:N and C:P in fine roots of evergreen species were significantly higher than those of deciduous species(P < 0.05).The specific root length(SRL),specific root area(SRA)and root diameter(TD)of fine roots of evergreen species were smaller than those of deciduous species,but there was no significant difference,the tissue density of fine roots(RTD)of deciduous species was significantly higher than that of deciduous species.In addition,the content of P and pH in rhizosphere soil of deciduous species were significantly higher than those of evergreen species.2.The fine root N,P content,specific root length,specific root area and cortex diameter ratio of evergreen and deciduous trees decreased with the increase of root order,while the root C content,root diameter,root tissue density,stele diameter and stele area ratio increased with the increase of root order.3.The results of this study showed that the scores of root nitrogen content(RootN),root phosphorus content(RootP),cortex thickness(CT),cortex diameter ratio(CDR)and root diameter(TD)on PCA axis 1 were 0.323,0.275,0.329,0.337,0.281,while the scores of C:N,root tissue density(RTD)and stele area ratio(SAR)of fine root in this axis were-0.310,0.290,-0.325.There was no significant correlation between specific root length(SRL)and most fine root traits(P > 0.05).The results of this study showed that the fine roots of evergreen trees adopted a relatively more conservative strategy,while the fine roots of deciduous trees adopted a relatively faster growth strategy;the nutrient and water absorption capacity of fine roots decreased with the increase of root order,while the transport and storage capacity increased;the root economic spectrum existed in fine roots of subtropical woody plants,but the(SRL)of specific root length needed to be excluded.In addition,soil C,N,P nutrients and stoichiometric ratio did not affect the position of fine root traits on the axis of root economic spectrum.