Integrated climate effects on nitrogen cycles in global grasslands.

Area of Science:

• Ecology
• Biogeochemistry
• Environmental Science

Background:

• Grasslands provide vital ecosystem services through biogeochemical processes.
• Challenges include improving grassland productivity, nitrogen use efficiency, and reducing nitrogen losses amidst climate change.
• Limited understanding exists on grassland nitrogen cycling responses to multiple climate change factors.

Purpose of the Study:

• To comprehensively assess the impact of multiple climate change factors on grassland nitrogen cycling globally.
• To identify the primary drivers of changes in nitrogen dynamics within grasslands.
• To project future changes in grassland nitrogen budgets and associated costs.

Main Methods:

• Analysis of data from 150 countries spanning 1980-2020.
• Comparison of scenarios with and without climate change impacts.
• Modeling future changes under the SSP2-RCP4.5 scenario for the year 2050.

Main Results:

• Climate warming is the primary driver of increased nitrogen harvest (19.8%), biological nitrogen fixation (8.8%), and nitrogen surplus (28.2%).
• Precipitation variability amplifies these nitrogen increases with spatial heterogeneity.
• Elevated atmospheric CO2 mitigates nitrogen surplus by enhancing plant nitrogen uptake.
• Projected annual increases by 2050: 22.3 million tonnes nitrogen input, 7.2 million tonnes harvest, 15.1 million tonnes surplus.
• Climate-induced nitrogen budget alterations may cost up to USD $69 billion.

Conclusions:

• Climate change significantly alters grassland nitrogen budgets, with warming as the main driver.
• Management strategies are urgently needed to mitigate negative climate change impacts on grassland nitrogen cycling.
• Addressing these changes is crucial for global sustainable development and ecosystem integrity.