Journal Article Soil 7440-44-0 Carbon Research Support, U.S. Gov't, Non-P.H.S. soil organic carbon 142M471B3J Arctic Carbon Dioxide N762921K75 National Wetlands Inventory Nitrogen Soil Survey Geographical blue carbon carbon coastal ecosystem respiration experimental warming grasslands gross primary productivity large herbivore grazing mangroves microbial biomass net ecosystem exchange permafrost pulse-chase experiments root exudation salt marsh subtropical pasture thaw