Research On Fine Root Traits And Soil Nutrients Of Larch,ash And Birch

In this study,Xing’an Larch(Larix gmelinii),Ash(Fraxinus mandshurica)and White birch(Betula platyphylla)were selected as study tree species in Maoer Mountain,Heilongjiang Province,China.Determined the contents of soil total carbon(STC),total nitrogen(STN),available nitrogen(AN),total phosphorus(STP)and available phosphorus(AP)in the root zone,the root average diameter(AD),specific root length(SRL),specific root area(SRA),root tissue density(RTD),specific root tips(SRT)and root tips per length(RTPL),and the root carbon(RC),root nitrogen(RN)and root phosphorus(RP)concentrations in fine root tissue of the three tree species.This study analyzed the rhizosphere effects and seasonal variation of soil nutrients,and the relationship between soil nutrient changes and fine root traits.This study could provide data and theoretical basis for rationally adjusting the stand structure of larch plantation.The main results are as follows:(1)ADs and SRLs of the three species were significantly different(P<0.05),ADs: Larch >White birch and Ash,and SRLs: Ash > White birch > Larch.The rhizosphere effects of STP and AP(RE-STP and RE-AP)of the three species were significantly different(P<0.05),both RE-STP and RE-AP were highest in larch.In addition,RE-STP was significantly associated with fine root traits,such as,there was a very significant positive correlation between the average root diameter and RE-STP(P<0.01),and SRL and SRT were significantly negatively correlated with RE-STP(P<0.05).(2)There were significant differences in RN concentrations and RP concentrations among the three tree species(P<0.05).And there was a significant positive correlation between RP and RN(P<0.01).The concentrations of RN and RP in the three tree species from high to low are:Ash > Larch > White birch.(3)During the growing season,the variation trends of soil P elements in the surface root zone of the three species were consistent,but the variation trends of soil N elements were inconsistent.The STN content of white birch decreased from April to September,reached the lowest point in early September,and then began to rise.The trend of AN content was the opposite.The contents of STN and AN in Larch and Ash showed a decreasing trend throughout the growing season.(4)Among the three tree species,the STC growing season variation index(VI-STC)of ash was the highest,and the STN growing season variation index(VI-STN)of white birch was the highest.In addition,RN concentration was significantly correlated with VI-C/N(P<0.01);and RP concentration was significantly correlated with VI-STN(P<0.05)and VI-C/N(P<0.01),respectively.Based on the root economic spectrum theory,fine root functional traits of ash are biased towards a “opportunistic” nutrient acquisition strategy,and larch’s traits are biased to "conservative" strategy.Larch has powerful P activation ability.The peak period of soil N uptake of or the requirement of N element of ash and larch might be different from that of white birch.