Consistent timelines, divergent end points: plant community change in multiple tallgrass nitrogen addition...

Area of Science:

• Ecology
• Environmental Science

Background:

• Human activities have globally increased nitrogen (N) bioavailability, affecting plant productivity and species richness.
• The dynamics and final composition of plant communities under N additions are not fully understood.

Purpose of the Study:

• To determine if plant community change with N addition is gradual or abrupt.
• To identify environmental drivers of short-term compositional changes.
• To map plant community end points after long-term N addition.

Main Methods:

• Synthesis of data from six long-term N addition experiments in tallgrass prairie.
• Analysis of plant community composition changes over time.
• Assessment of environmental perturbations (precipitation, herbivory, fire) as catalysts for change.

Main Results:

• Most plant community change occurred gradually over several years of chronic N addition.
• No evidence suggests other perturbations catalyzed N-driven compositional changes.
• Final community composition varied across experiments, influenced by initial conditions.
• Dominant species in N-added communities were fast-growing, weedy species.

Conclusions:

• Plant community shifts in response to N addition are gradual and influenced by initial species composition.
• Long-term experiments are crucial for understanding N addition impacts, as short-term studies may underestimate responses.
• Altered N bioavailability can lead to significant shifts in tallgrass prairie plant communities, potentially affecting ecosystem function and stability.