Does synergy among litter, organic horizons, and roots bolster nutrient retention and production?

Temperate forests are under increasing environmental stresses from changes in land management, atmospheric pollution, and a changing climate. These environmental changes have important effects on how inorganic nutrients (Magnesium, Phosphorus, Potassium, Calcium) are stored and cycled in the soils of temperate forests. Inorganic nutrients are essential for plant growth and are sourced to soils from mineral weathering, deposition from the atmosphere, and leaf litter from plants.

While roots are known for their role in extracting inorganic nutrients for plants, they can contribute organic matter to help store inorganic nutrients in soils. This research project explores how leaf litter and surface roots promote inorganic nutrient storage in soils and the extent of their codependence. To understand climatic controls on leaf litter and roots for inorganic nutrient cycling, the researchers will leverage a network of research sites spanning from the warm temperate forests of Virginia to the cold temperate forests of northern New England.

The findings will be used to inform the U.S. Forest Service and several state Forestry and Natural Resources Departments of the current and future inorganic nutrient cycling in their forests. Furthermore, the research site in Massachusetts will serve as an instructional tool for university and community college courses.

The primary objective of the project is to quantify the codependence of leaf litter and roots on Mg, P, K, and Ca stabilization in temperate forest soil. Leaf litter and roots may act synergistically to stabilize inorganic nutrients in the mineral soil through generating organic matter and aggregation. To avoid the common issue of heterogeneity of soil materials and duration of development, the project will leverage soil columns buried three years ago, containing a quartz-feldspar-kaolinite mixture to examine the effect of leaf litter and tree roots on inorganic nutrients in mineral soil.

Researchers will quantify the rate of inorganic nutrient stabilization in bulk soils and use microprobe analyses to examine rhizosphere and microaggregation. Moreover, the project will utilize existing litterfall and atmospheric deposition monitoring to estimate nutrient cycling budgets. When examined across the climate gradient, the findings can be used to predict future shifts in nutrient cycling from shifts in leaf litter-root codependence with changes in climate.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.