Nitrogen losses from perennial grass species

Area of Science:

• Plant Ecology
• Nutrient Cycling
• Isotope Tracing

Background:

• Nitrogen loss from plants is crucial for ecosystem nutrient dynamics.
• Previous studies primarily quantified nitrogen loss via above-ground litter.
• Below-ground nitrogen loss pathways remain under-quantified.

Purpose of the Study:

• To quantify total nitrogen losses, including below-ground pathways, using 15N pulse labeling.
• To test if plant species from nutrient-poor habitats exhibit lower nitrogen losses than those from fertile soils.
• To compare nitrogen loss strategies across six perennial grass species.

Main Methods:

• Utilized 15N pulse labeling to track nitrogen movement and loss.
• Conducted greenhouse experiments with perennial grasses (Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra, F. ovina, Molinia caerulea) at two fertility levels.
• Differentiated nitrogen loss through above-ground litter versus below-ground pathways (root turnover, leaching, exudation).

Main Results:

• Significant nitrogen losses occurred through pathways other than above-ground litter production.
• In low fertility, Lolium perenne lost most nitrogen via litter (70%), while other species lost >50% below-ground.
• Increased nutrient supply elevated above-ground losses and decreased below-ground losses in some species.
• Nitrogen loss varied significantly among species, with a distinct ranking based on turnover coefficients.

Conclusions:

• Plant species adapted to nutrient-poor environments demonstrate reduced overall nitrogen loss compared to those from fertile soils.
• Below-ground nitrogen loss is a significant, often dominant, pathway, especially in species from low-nutrient habitats.
• Nutrient availability influences the relative importance of above- and below-ground nitrogen loss pathways.