Grassland biodiversity bounces back from long-term nitrogen addition

Area of Science:

• Ecology
• Environmental Science
• Botany

Background:

• Atmospheric nitrogen (N) pollution negatively impacts grassland biodiversity.
• UK cleaner technologies have reduced nitrogen oxide emissions and N deposition.
• Uncertainty exists regarding grassland biodiversity recovery after reduced N deposition.

Purpose of the Study:

• To investigate grassland biodiversity response to reduced N addition.
• To assess if long-term N addition leads to an irreversible low biodiversity state.
• To evaluate the effectiveness of reduced N inputs on biodiversity recovery.

Main Methods:

• Analysis of data from the 160-year-old Park Grass Experiment.
• Monitoring changes in legume proportion, species richness, and diversity.
• Comparing plots with reduced N deposition (atmospheric and fertilizer) over time (1991-2012).

Main Results:

• Biodiversity (legume proportion, species richness, diversity) increased as N deposition declined.
• Grassland plots ceasing inorganic N fertilizer in 1989 showed significant diversity recovery, especially when limed.
• No evidence of an alternative low biodiversity state due to chronic N addition, except in cases of extreme acidification.

Conclusions:

• Reducing N addition, from pollution or fertilizers, positively impacts grassland biodiversity.
• Long-term N addition does not necessarily lead to an irreversible low biodiversity state.
• Biomass removal through mowing likely facilitates plant community recovery, explaining differences with the wider landscape.