Soil warming alters nitrogen cycling in a New England forest: implications for ecosystem function and structure

Area of Science:

• Ecology
• Climate Change Science
• Forestry

Background:

• Global climate change influences terrestrial ecosystems through biogeochemical feedbacks.
• Effects of climate change on soil-plant process linkages are less understood than greenhouse gas feedbacks.
• Understanding these linkages is crucial for predicting ecosystem responses to warming.

Purpose of the Study:

• To investigate the effects of experimental soil warming on nitrogen cycling in a deciduous forest.
• To assess the impact of altered nitrogen availability on tree growth and species composition.
• To determine species-specific responses to warming-induced changes in the nitrogen cycle.

Main Methods:

• A long-term field manipulation experiment involving continuous soil warming (5°C above ambient) for 7 years.
• Monitoring of nitrogen mineralization and nitrification rates.
• Measurement of foliar nitrogen content and relative tree growth rates.

Main Results:

• A 45% average annual increase in net nitrogen mineralization.
• A three-fold increase in nitrification, with 25% of mineralized nitrogen being nitrified in later years.
• Increased foliar nitrogen content and relative growth rates in trees within the warmed area.
• Acer rubrum (red maple) exhibited the most pronounced increases in foliar nitrogen and growth rates.

Conclusions:

• Soil warming alters forest nitrogen cycling, increasing nitrogen availability and promoting tree growth.
• Species-specific responses to nitrogen changes are critical for predicting future forest composition under climate change.
• Understanding these dynamics is essential for forecasting ecosystem feedbacks to the climate system.