Study On Vegetation Biomass And Carbon And Nitrogen Storage In Primary Succession Stage Of Hailuogou Glacier Retreating Area

Knowledge on vegetation primary succession is important for a better understanding on the structure and function of ecosystems and is key for the restoration of degraded ecosystems.Retreating of Hailuogou glacier in the past 130 years leaves a completely vegetation successional chronosequence which provided an ideal place to investigate the mechanism of primary vegetation succession.In this study,the species composition and biomass of vegetation from the top layer(trees),middle layer(shrubs)and bottom layer(herbs)along the successional chronosequence were investigated.In addition the vegetation carbon and nitrogen storages were measured.Results indicated that:1)Totally 68 species,31 families,58 genera,and 27 species of plants were recorded in the Hailuogou glacial retreat area.According to the classification based on Wu Zhengyi(2003),the seed plants belongs to 31 families in the study area could be divided into five types of distribution areas and three variants,and seed plants(except ferns)can be classified into 8 distribution types and 3 variants according to Wu et al.(1991).2)The biomass models descript the trunk and the aboveground biomass better than the branches,leaves and belowground biomass,with a better estimation of binary model with tree height(H)than that of the unary model.Comparatively,model with a independent variable of D²H had a better prediction on biomass of trunk and aboveground biomass,while that of D³/H had a better prediction on the leaf and root biomasses.Unigram models were recommended only if the accuracy of prediction of models was not required.3)Plant biomass increased along with the succession chronosequences,ranged from 0.95t·hm^-2(herb only)in the very early succession stage to 186.608t·hm^-2 in late stages.Among the communities,trees accounted for the largest proportion of total biomass(>83.804%),shrubs accounted for 1.66%-15.09%and herbs accounted for0.09%-1.97%of total biomass.The distribution of biomass with tree organs ordered as dry>root>branche>leaf.4)The mean carbon concentration of the shrub and tree organs was 44.82±0.68%,ranged from 39.56%to 50.2%and with a averaged value of 45.02±2.6%,45.69±1.62%and 43.77±1.43%,respectively,in the leaves,stems and roots..Conifersous relative to broadleaf species had a higher carbon concentration in their organs.Herbs with a averaged carbon concentration of 42.13±0.27%was slightly lower than that of the shrubs.The mean nitrogen concentration of the plants in the deglaciered area was 1.25±0.71%,ranged from 0.92-2.72%among different species.Hippophiae relative to other species had an onviously higher nitrogen concentration(2.72±0.88%of N concentration in Hippophiae plants,v.s.0.92-1.39%in other plant species).The average nitrogen concentration was 2.12±0.52%,0.87±0.17%and 0.77±0.15%,repspectively,in tree leaves,trunks and roots.Herb with an N concentration of 1.41±0.56%was slightly higher than the averaged nitrogen concentrations in the shrubs.5)Vegetation carbon storage showed a similar trend with that of biomass along the successional chronosequence,with a extremely low amount(0.398t·hm^-2)at the early succession stage and maximumed(102.3t·hm^-2)in the late succession stage.Among palnt communities,trees with a carbon storage of 11.07-99.85 t·hm^-2 account for 84.559%to97.602%of carbon storage in the ecosystes,shrubs with a carbon storage of 0.66-4.41t·hm-2 account for 1.626%-14.453%,and herbs with a carbon storage of 0.072-0.698t·hm-2 account for less than 2%of carbon storage of the ecosystems.Similarly,vegetation nitrogen storage increased from 0.014t·hm^-2 at the early succession stage and to 1.763t·hm^-2at the late succession stage.Trees with a carbon storage of 0.68-1.98 t·hm^-2 accounted more than 90%off carbon storage in the ecosystes,shrubs with a carbon storage of 0.016-0.109 t·hm^-2account for 1.032%-8.814%,and herbs with a carbon storage of 0.005-0.026 t·hm^-2 account for less than 3%of nitrogen storage of the ecosystems.