| As the functional organ of trees,fine roots being used to absorb nutrients and water,play an important role in C and N cycle in forest ecosystem.This study took Castanopsis eyrei natural forests in Wuyishan Nature Reserve as research objects,used drilling core method study systematically on spatial and temporal variety regulation of Castanopsis eyrei natural forests fine root eharacteristic parameters such as biomass,specific root length,surfaee area,volume density,root length density,and on relationships between these parameters and soil nutrients including organic matter total N,total P and total K among four elevations in Wuyishan Nature Reserve,which aimed at revealling the vertical variation of fine roots indexes of correlation in Castanopsis eyrei natural forests,further exploring the relationship between fine root structure parameters and and soil environment in order to provide some reference for trees roots in the future.The main findings include the following aspects:(1)Vertical variation of fine root biomassEffects of soil layers on fine root biomass showed significant differences(P<0.01),fine root biomass on each soil layers manifest that fine root biomass reduced with soil depth increasing,in which 0?10 cm accounted for 50%and more of 0?30 cm total biomass;There was no significant differencebetween altitude and fine root biomass(P>0.05).Fine root biomass among 4 elevations showed the consistent discipline,that is 0?10 cm>10?20 cm>20?30 cm,but fine root biomass in different altitude exist large differences.From fine root biomass about various altitudes,its order of size was:1000 m>1200 m>800 m>600 m>Effects of fine root diameter on fine root biomass showed no significant differences(P>0.05).With soil depth varying,fine root biomass of each different diameter showed differences among different altitudes,but fine root biomass of each diameter diminished,when soil depth increased.(2)Vertical distribution of specific root length(SRL)specific surface area(SRA),root volume density,root length density of fine rootThree different soil layers have different SRL on each altitude.600 m,800 m and 1000 m altitudes,Castanopsis eyrei fine root SRL increases with soil depth deepening,but at altitude of 1200 m,its SRL increased(0?20 cm),then reduced(20?30 cm)with soil depth increasing,but extent was smaller.Overall trend was that with the soil depth deepening,SRL rising among different altitudes.Impact of altitude and soil layer on fine root SRL both were significant(P<0.01)Fine root SRA of Castanopsis eyrei in each elevation presents enhancive,when the soil depth increases,in which the biggest variation tendency was at altitude 600 m.Elevation has a very significant effect on SRA of each soil layer(P<0.01).However,SRA exist differences between the soil layers at different altitudes.For example,at the altitude of 600 m and 1000 m,the soil layer has very significant effect on fine root SRA(P<0.01),while at the altitude of 800 m and 1200 m,the impact of soil layer on the fine root SRA was nosignificant(P>0.05).Volume density of Castanopsis eyrei fine roots decline with the soil depth deepening,but in four altitudes,the sharpest reduction of fine root volume density was at altitude 1000 m.At the 0-10 cm soil layer,altitude showed extremely significant differences on fine root volume density(P<0.01);however,at the 10?20 cm and 20?30 cm soil layers,there was no significant effects(P>0.05).Soil depth had significant effects on volume density of fine roots in different altitudes(P<0.01)Regardless of which elevation,fine roots length density maximum of Castanopsis eyrei was at the 0-10 cm soil layers;and with the soil depth increasing,fine roots length density showed decreased.At 0?10 cm and 10?20 cm soil layers,elevation has an extremely significant effect(P<0.01)on fine roots length density;and at 20?30 cm soil layers,altitude only showed significantly(P<0.05).Besides,the influence of soil depth to fine roots length density exists otherness,and soil layer has a significant effect on fine roots length density for four elevations(P<0.05)(3)Diameter characteristics of fine root length,root surface area and root volumeIn the three soil layers of different altitudes,the diameter class of 0?2 mm had the maximum contributions to the total root length,surface area,volume.And the diameter class of 0?1 mm had higher contribution to the total root length,surface area,volume than 0?2 mm diameter fine foot class.The root length,surface area,volume of root d>2 mm accounted for a small proportion,which accounted for less than 10%(4)Vertical distribution law of C,N content and C/N ratio of fine rootThe interaction of fine root diameter and altitude had no significant effect on N content(P>0.05),but the altitude had significant effect on N content(P>0.05),and the diameter of root class had highly effect on N content(P<0.01).Except the altitude of 1000m,the N content of fine root 0<d<1 mm was higher than root diameter 0<d<lmm in the altitude of 600m,800m and 1200m.And in the three soil layers of different altitudes had showed the same rule.In addition,the interaction of fine root diameter and soil depth had no significant effect on N content.The interaction of fine root diameter and altitude had no significant effect on C content(P>0.05),and the C content of fine root,the diameter class had no significant effect on C content,respectively.The interaction of fine root diameter and soil depth had no significant effect on C content;however,the diameter class had significant difference to the total C content of fine root.Apart from the altitude of 1200 m,the C content of fine root 0<d<1 mm was higher than root diameter 0<d<1mm in others altitudesThe interaction of fine root diameter and altitude had no significant effect on C/N ratio,(P>0.05),but the altitude had highly significant difference in C/N ration(P<0.01).The factors of altitude and fine root diameter had highly significant effect on C/N ration(P<0.01).In addition to the altitude of 1000 m,the C/N ratio of fine root 0<d<1mm was higher than root diameter 0<d<1 mm in others altitudes,and in the three soil layers of different altitudes had showed the same rule.(5)Research on the relationship between fine root structure and soil nutrientsThe result showed that the correlation of fine root biomass with soil nutrients were various at different altitudes in Castanoppsis eyrei forest.Such as at an altitude of 600m and 1000m,the relationship between fine root biomass and soil organic matter was not significant positive correlation.However,at altitudes of 800 m and 1200 m,fine root biomass and the distribution of soil organic matter had significantly positive correlation;at the altitude of 800 m,fine root biomass and soil total nitrogen,total phosphorus was significantly positively correlated,but at an altitude of 1000 m,fine root biomass and soil nitrogen was not significant positive correlation.Fine root biomass and soil total nitrogen had no significant positive correlation,in addition,had significant positive correlation with phosphorus,and had significant negative correlation with the total potassium;At the altitude of 1200 m,fine root biomass and total nitrogen,total phosphorus showed a highly significant positive correlation,and had no significant negative correlation with total potassium;In the soil layer of 0?10 cm depth,fine root biomass had no significant correlation with soil nutrients,in the depth of 10?20 cm depth,fine root biomass had significant positive correlation with soil organic matter and nitrogen,but had significant correlation with soil total phosphorus and total potassium. |
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