Journal Article Research Support, Non-U.S. Gov't 7440-44-0 Ammonium Compounds Carbon China Fertilizers N762921K75 Nitrates Nitrogen Soil Tibetan Plateau Visible Infrared Imaging Radiometer Suite (VIIRS) active fires alpine grassland alpine meadow biodiversity and stability climate change eddy covariance functional groups grassland biomass production grassland management gross primary productivity herbivory interannual variability model tree ensemble nitrogen chemical form occurrence frequency priming effect soil microbes