Carbon And Nitrogen Variations In Fine Roots And Rhizosphere Soil Supporting Three Types Of Vegetations Restored In Degraded Red Soil Area

Forest ecosystem is an important part of terrestrial ecosystem.The effects of different vegetation restoration patterns on soil carbon and nitrogen were different.Especially the relationship between soil and root,that made the nitrogen and organic carbon of soil and root in different forests quite different.artificial mixed broadleaf-conifer forest was taken as the control with artificial mixed broadleaf forest and natural mixed broadleaf-conifer forest research subjects.I studied the fine root,rhizosphere and non-rhizosphere soil total organic carbon and total nitrogen,water soluble organic carbon and total nitrogen to explore the relationship between them.Conclusions are as follows:(1)The content of total organic carbon and total nitrogen in rhizosphere and non rhizosphere both decreased with the increase of soil depth.In 0-10 cm and 10-20 cm soil layer,Soil total organic carbon content in non rhizosphere of artificial mixed broadleaf-conifer forest and artificial mixed broadleaf-conifer forest was significantly higher than that ofnatural mixed broadleaf-conifer forest.But there was no significant difference in the total organic carbon content of the three vegetations restoration in the rhizosphere soil.The content of total nitrogen in rhizosphere and non-rhizosphere soil was low.The contents of total nitrogen in rhizosphere and non rhizosphere soil ofnatural mixed broadleaf-conifer forest and artificial mixed broadleaf forest were all higher than that of artificial mixed broadleaf-conifer forest in 0-10 cm soil layer,but in 20-40 cm and 10-20 cm soil layer have the opposite result.with the increase of soil depth the difference between organic carbon content in non rhizosphere and rhizosphere soil decreased gradually in all the three vegetation restorations.(2)The WSOC content in the rhizosphere soil was generally less than that of the non rhizosphere soil.WSON in non rhizosphere soil of artificial mixed broadleaf-conifer forest was larger than that of rhizosphere.butnatural mixed broadleaf-conifer forest on the contrary.The WSOC of artificial mixed broadleaf forest in non rhizosphere soil is greater than the rhizosphere in 0-10 cm soil layer,while the 20-40 cm soil layer was larger in rhizosphere soil.The content of WSOC in rhizosphere soil was artificial mixed broadleafconifer forest >natural mixed broadleaf-conifer forest >artificial mixed broadleaf forest,The order of WSOC content in the non rhizosphere soil was natural mixed broadleaf-conifer forest >artificial mixed broadleaf-conifer forest >artificial mixed broadleaf forest in 0-10 cm and 10-20 cm soil layer.while the 20-40 cm soil layer is Artificial mixed broadleafconiferforest >artificial mixed broadleaf forest >natural mixed broadleaf-conifer forest.The difference of WSOC content in the three soil layers ofnatural mixed broadleaf-conifer forest in non rhizosphere soil was greater than that of artificial mixed broadleaf-conifer forest and artificial mixed broadleaf forest,WSON content of rhizosphere soil is natural mixed broadleaf-conifer forest >artificial mixed broadleaf forest >artificial mixed broadleafconifer forest,but the WSON content of the non rhizosphere soil is opposite.(3)The relationship between WSOC and TOC of both natural mixed broadleaf-conifer forest and artificial mixed broadleaf forest in rhizosphere and non rhizosphere soil was significant or extremely significant,the relationship in artificial mixed broadleaf-conifer forest is not significant.There was a significant correlation between the rhizosphere and non rhizosphere soil in WSOC content of the three vegetation restoration.WSON and TN showed significant or extremely significant correlation in all the three vegetation restoration.The WSON or TN in Rhizosphere l had significant or extremely significant correlation with the one in non rhizosphere soil.WSOC/TOC in non rhizosphere soil was greater than that in rhizosphere soil,and gradually increase with the increase of soil depth.WSON/TN of artificial mixed broadleaf-conifer forest in rhizosphere soil is higher than that of non rhizosphere soil,and artificial mixed broadleaf forest andnatural mixed broadleafconifer forest are on the contrary.TOC/TN of rhizosphere soil decreased with the increase of soil depth.but the law of non-rhizosphere soil was not obvious,WSOC/WSON in non rhizosphere soil is larger than that of rhizosphere soil in three vegetation restoration.(4)the fine root biomass in 0-40 cm layer is natural mixed broadleaf-conifer forest(1814.89kg/hm2)>artificial mixed broadleaf-conifer forest(887.99kg/hm2)>artificial mixed broadleaf forest(751.34kg/hm2),The diameter of the <0.5mm root of three vegetation restoration patterns have accounted for the largest proportion of fine roots.Fine root biomass showed obvious seasonal variation,artificial mixed broadleaf-conifer forest showed a trend of double peaks,peaks appear in May and December respectively and artificial mixed broadleaf forest is presented as a single peak type,peak appeared in October.natural mixed broadleaf-conifer forest's fine roots did not change significantly with the seasons.The total organic carbon content of fine root and water soluble carbon content generally showed artificial mixed broadleaf-conifer forest>natural mixed broadleaf-conifer forest >artificial mixed broadleaf forest,Fine organic carbon was mainly affected by the fine root biomass.The total nitrogen of artificial mixed broadleaf forest 's fine root was significantly higher than that of artificial mixed broadleaf-conifer forest.but the difference of water soluble organic nitrogen content of the three vegetation restoration modes was small,their content was in the range of 1.88-2.25g/kg,the order of total organic nitrogen of fine roots was natural mixed broadleaf-conifer forest>artificial mixed broadleaf forest >artificial mixed broadleaf-conifer forest,which had the same order with the fine root biomass.(5)We can carry out certain closed cultivation for artificial mixed broadleaf-conifer forest or planting some broad-leaved species in it or we can plant some planting some broadleaved species in natural mixed broadleaf-conifer forest.