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Harvard Forest REU Symposium Abstract 2023
- Title: Going Underground: Effects of Soil Warming and Nitrogen Addition on Root Exudation Rates of Arbuscular and Ectomycorrhizal Associating Trees in Harvard Forest
- Author: Isa E Gooijer (Harvard University)
- Abstract:
Harvard Forest is a carbon sink. However, the question remains if it will continue to be a carbon sink as the climate changes and temperature rises. Through root exudation trees ‘leak’ carbon into the soil which impacts the carbon cycling of the forest. Root exudation is a mechanism that trees use to enhance their nutrient uptake (e.g., nitrogen). Trees provide carbon to soil microbes to promote mineralization which increases inorganic nitrogen availability. The tree takes up and uses this inorganic nitrogen for growth and survival. Previous research at Harvard Forest found that trees decrease their root exudation rates in response to soil warming. The strength of the response was dependent on the mycorrhizal fungi type they associate with. In Harvard Forest trees predominantly associate with either of two types of mycorrhizal fungi: ectomycorrhizal (EM) or arbuscular mycorrhizal (AM) fungi, which specialize in organic and inorganic nutrient economies, respectively. Currently, the soil is rich in organic nitrogen, but soil warming might increase the inorganic nitrogen availability. So, whereas EM associating trees thrive in the current organic nitrogen rich environment, AM associating trees might gain an advantage as inorganic nitrogen becomes more available in warmed soil. Therefore, this summer we hypothesized that the observed response is the result of a shift in nutrient economies from organic to inorganic. We collected root exudates from EM and AM associating trees from heated plots, nitrogen fertilized plots and heated+nitrogen fertilized plots to test if the effect was the result of soil warming, increased inorganic nitrogen availability or a combination of both. I anticipated the exudation rate for heated and nitrogen plots to decrease at similar rates for both types of trees (AM and EM). Our research contributes to understanding how root exudation rates of AM and EM trees are affected by climate change and how that impacts the carbon cycle.
- Research Category: Soil Carbon and Nitrogen Dynamics
