Grassland ecosystems account for more than 10% of the global CH4 sink in soils. A 4-year field experiment found that addition of P alone did not affect CH4 uptake and experimental addition of N alone significantly suppressed CH4 uptake, while concurrent N and P additions suppressed CH4 uptake to a lesser degree. A meta-analysis including 382 data points in global grasslands corroborated these findings. Global extrapolation with an empirical modeling approach estimated that contemporary N addition suppresses CH4 sink in global grassland by 11% and concurrent N and P deposition alleviates this suppression by 6%. The P alleviation of N-suppressed CH4 sink is primarily attributed to substrate competition, defined as the competition between ammonium and CH4 for the methane monooxygenase enzyme. The N and P impacts on CH4 uptake indicate that projected increases in N and P depositions might substantially affect CH4 uptake and alter the global CH4 cycle.
Dew plays a crucial role in ecosystem processes in arid and semiarid regions, and is expected to be affected by climate warming. However, how warming simulation affects dew formation has been long ignored and rarely addressed. We measured dew amount and duration and plant traits related to dew condensation from 2012 to 2017 in a long-term infrared warming experiment in an alpine grassland of Tibetan Plateau. The results showed that (1) warming reduced the dew amount by 42%-91% and reduced dew duration by 32 days compared to the ambient condition. (2) Plant functional groups differed in dew formation. (3) Under the warming treatment, the dew amount decreased with plant height; while under the ambient conditions, the dew amount showed the opposite trend. Warming using an infrared heater system greatly reduces dew formation, which if overlooked, could lead to overestimation of climate warming impacts on ecosystem processes.