Grassland productivity limited by multiple nutrients.

Area of Science:

• Ecology
• Biogeochemistry
• Plant Science

Background:

• Terrestrial ecosystem productivity is widely accepted to be nutrient-limited.
• Nitrogen (N) is a key determinant of aboveground net primary production (ANPP), but co-limitation by N and phosphorus (P) is increasingly recognized.
• The extent of co-limitation by nutrients other than N and P remains unclear.

Purpose of the Study:

• To investigate the prevalence of nutrient limitation and co-limitation in terrestrial ecosystems.
• To assess the roles of nitrogen (N), phosphorus (P), potassium (K), and micronutrients in limiting grassland ANPP.
• To understand geographical variations in nutrient limitation.

Main Methods:

• Conducted a standardized factorial nutrient addition experiment across 42 grassland sites on five continents.
• Added N, P, and K combined with micronutrients (K+μ), alone or in concert.
• Monitored aboveground net primary production (ANPP) in response to nutrient additions.

Main Results:

• Nutrient availability limited productivity at 31 of the 42 grassland sites.
• Pairwise combinations of N, P, and K+μ co-limited ANPP at 29 sites.
• Nitrogen limitation was most pronounced in cool, high-latitude regions.

Conclusions:

• Less studied nutrients, such as potassium (K) and micronutrients, are crucial for grassland productivity.
• Significant variations exist in the type and degree of nutrient limitation across ecosystems.
• Multiple nutrient constraints must be considered for assessing ecosystem-scale consequences of nutrient enrichment.