Phosphorus alleviation of nitrogen-suppressed methane sink in global grasslands.

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, whereas 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 modelling approach estimated that contemporary N addition suppresses CH4 sink in global grassland by 11.4% and concurrent N and P deposition alleviates this suppression to 5.8%. 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 mono-oxygenase 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.

Effects of Increased Nitrogen and Phosphorus Deposition on Offspring Performance of Two Dominant Species in a Temperate Steppe Ecosystem.

Plants adapt to environment by plastic growth which will be transferred to offspring through transgenerational effect. Performance and response of maternal and offspring plant will affect population dynamics and community composition. However, it is scarcely understood how maternal nutrient environment affect the performance and response of offspring through transgenerational effect. Here we studied the impacts of nitrogen (N) and phosphorus (P) enrichment on maternal and offspring performances and responses of Stipa krylovii and Artemisia frigida. Seeds were collected from maternal plant experiencing N or/and P addition for three years in Inner Mongolia grassland. We found that maternal nutrient addition significantly affected seed traits, offspring biomass, and offspring responses of A. frigida. Maternal N addition significantly affected maternal reproductive biomass, seed traits of S. kryloii. Maternal P addition of S. kryloii significantly affected seed qualities, seedling biomass and seeding response to N addition. Our results suggested that transgenerational effects of N and P enrichment to the two dominant plant species existed in this ecosystem. Furthermore, the two species exhibited different adaptive strategies to future nutrient addition. These findings indicate that maternal environmental effect should be considered into the model projection of vegetation dynamics in response to ongoing environmental change.