Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs.

Area of Science:

• Ecology
• Plant Trait Ecology
• Ecosystem Function

Background:

• Leaf traits are widely used in ecology as a common currency to predict ecosystem responses to anthropogenic pressures.
• Understanding trait plasticity and consistency across diverse environments is crucial for ecological forecasting.

Purpose of the Study:

• To test the consistency of leaf trait responses to experimental nutrient additions and herbivore exclusion across 27 global grassland sites.
• To evaluate whether specific leaf area is a reliable indicator of plant responses to anthropogenic perturbations in grasslands.

Main Methods:

• Experimental soil nutrient additions and vertebrate herbivore exclusion were implemented across 27 grassland sites on 4 continents.
• Measurements included specific leaf area, leaf nitrogen, phosphorus, and potassium concentrations.
• Statistical analyses examined trait responses to treatments, correlations with species turnover, and influence of climate and soil conditions.

Main Results:

• Specific leaf area did not consistently respond to nutrient additions over four years.
• Leaf nitrogen, phosphorus, and potassium concentrations increased with the addition of their respective nutrients.
• Few significant short-term changes in leaf traits were observed upon herbivore exclusion.
• Leaf nitrogen and potassium concentrations correlated with species turnover, but not leaf phosphorus.

Conclusions:

• Specific leaf area is not a universally appropriate indicator for assessing grassland responses to anthropogenic perturbations.
• Leaf nutrient concentrations provide more consistent signals of environmental change in grasslands.
• Interspecific trait variation, climate, and soil conditions significantly influence leaf trait expression.