Biomass Allocation Pattern And Its Influcing Factors Across Typical Terrestrial Ecosystems In China

Biomass directly reflects the ecosystem production and have been regarded as an important part of the terrestrial ecosystem carbon stocks.Root:shoot ratio(R/S)plays a critical role in global carbon cycle.However,current biomass allocation patterns and their response to environmental factors are still unclear in terrestrial ecosystems of China.Researches about the biomass allocation pattern and its influence factors in this wide area are needed to provide reliable data support and theoretical basis for the terrestrial ecosystem carbon budget assessment.In this paper,we established a biomass database of typical terrestrial ecosystems in China by collectiong data from more than 1800 literatures about biomass allocation in desert and wetland ecosystems,combined with the biomass dataset of forest and grassland ecosystems.Based on the database,we analyzed the spatial pattern of AGB(aboveground biomass),BGB(belowground biomass)and R/S ratio in typical terrestrial ecosystems of China and their responses to biotic and abiotic factors.The main conclusions are as followings:(1)Biomass and R/S changed significantly among various vegetation types.The broad-leaved forests had highest biomass among various forest ecosystems.For grassland ecosystem,R/S ratio was found to be lowest in mountain meadow.For desert ecosystems,R/S of heavy drought desert was higher than that of light and moderate drought desert.For wetlands,coastal wetland had higher AGB and marsh wetland has highest R/S ratio.(2)Spatial distribution of AGB,BGB and total biomass showed similar trends in china,decreasing from the southeast to the northwest.In addition,R/S showed clearly regional variations and was divided by the line of Greater Khingan,Inner Mongolian Plateau and Tibetan Plateau.(3)Responses of AGB,BGB and R/S to biotic and abiotic factors were different among various terrestrial ecosystems.Stand age showed the strongest effect on the biomass of forest ecosystem.R/S ratio was mainly determined by mean annual temperature(MAT)and stand density in coniferous forests,and by MAT and mean annual precipitation(MAP)in broad-leaved forests.However,stand age was the main factor that determined R/S ratio in mixed forests.In grassland ecosystems,mean annual evaporation was the main factors that affects the biomass of temperate grassland,whereas soil total nitrogen had significant effect on the biomass of alpine grassland.MAT and soil total phosphorus had significant effect on the biomass of desert ecosystem.However,climate and soil characteristics had less impact on R/S of grassland and desert.Besides,SOC and MAT were the main determination of biomass in wetlands.R/S in coastal wetlands was strongly influenced by MAT and soil salinity while that in inland wetland was mainly affected by MAT and soil organic carbon.