Research

Forest Resilience to Climate Change

Our research investigates the effects of climate change on the structure of natural plant communities, with a particular focus on forests. Forests are essential systems for understanding climate change because tree species respond to environmental change over long timescales and across large geographic areas. Our research identifies combinations of factors that place tree species at risk of local extinction under climate change, with particular attention to constraints on species recruitment, the process by which new individual trees establish and survive. Our research also identifies potential source regions for immigrant tree species, meaning the geographic areas from which tree populations could migrate into a given region as climate conditions shift. In addition, our research examines the resilience of current forests to water loss and productivity loss under climate change (Requena-Mullor et al. 2023).

Vulnerability to Biological Invasions

Invasive species science has historically focused on the invasive species itself, meaning the non-native organism causing ecological disruption. However, protecting native species from biological invasions also requires a proactive approach that focuses on resident native communities and the features that make these communities vulnerable to invasion impacts. Vulnerability to biological invasions results from factors acting across multiple spatial scales, ranging from local to regional. The combined effects of these local and regional factors determine the overall magnitude of a native community's vulnerability to invasion. Here, we introduce an analytical framework that quantifies the scale-dependent impact of biological invasions on native species richness. This framework is based on the shape of the native species-area relationship (SAR), a mathematical relationship describing how the number of native species increases with the area of habitat sampled.

Tree Growth Responses Under Elevated CO2 - The Role of Mycorhizal Fungi

Mycorrhizal association type — arbuscular mycorrhizal (AM) versus ectomycorrhizal (EM) — influences how elevated atmospheric CO2 (eCO2) enhances plant growth and net primary productivity (NPP), because the type of mycorrhizal fungi a plant associates with determines how much nitrogen (N) that plant can access. Nitrogen is commonly the nutrient that limits plant growth, so nitrogen access is a central mechanism driving plant growth responses to eCO2. Ectomycorrhizal fungi (EMF), which are common in low-nitrogen soils, can access nitrogen bound in soil organic matter (SOM) by producing extracellular enzymes that break it down. Arbuscular mycorrhizal fungi (AMF) lack the genes needed to produce these extracellular enzymes and therefore cannot access nitrogen from soil organic matter. Because of this physiological difference between ectomycorrhizal fungi and arbuscular mycorrhizal fungi, we tested two hypotheses: first, that when inorganic nitrogen supply is low, the eCO2 growth response of EMF-associated plants is less nitrogen-limited than that of AMF-associated plants, since AMF-associated plants depend on inorganic nitrogen and cannot draw on nitrogen stored in soil organic matter; and second, that this difference in nitrogen-acquisition strategy between EMF and AMF shapes how mycorrhizal association type affects plant responses to elevated CO2.