Current and Past Research Projects
Nitrogen cycling in tropical montane forests
This work addresses a question that is fundamental to understanding how global tropical forests function and how they are represented in earth system models—how does climate affect forest nutrient cycling and carbon storage?
Tropical mountains give rise to some of the most striking climatic and ecological gradients on Earth. Over relatively small distances, elevational gradients in tropical mountains recapitulate latitudinal shifts in temperature and thus provide a natural laboratory for understanding environmental control of ecosystem function and effects of global change. In this study, we use multiple lines of evidence to conclude that tropical montane forest soils hold a large pool of nitrogen that is highly sensitive to warming
Through the use of forest elevational gradients across tropical regions we 1. quantify the distribution of forest soil N across tropical mountains 2. assess the topographical and climatic controls over surface soil N and δ15N (a proxy for N availability and long-term N cycling).
We find a globally consistent pattern of increasing soil N concentrations and decreasing δ15N with increasing elevation that is driven primarily by temperature constraints on microbial N mineralization and denitrification that result in lower ecosystem-level gaseous N losses. Moreover, we show that montane forests account for an outsized proportion of the tropical forest soil N pool and that these pools exceed previous global estimates by nearly two-fold (!).
Taken together, our results identify a large and potentially vulnerable pool of soil nitrogen to future climate warming in tropical latitudes. Moving forward, I am working on evaluating the extent montane tropical forests have warmed over the last 25 years and how this has impacted tropical forest productivity.
Figure 1. Global tropical mountain distribution (Row 1 green shaded), soil nitrogen pool (row 2) and δ15N (row 3). From Gay et al. 2022.
Disentangling how soil disturbance and climate change impact subalpine grassland community structure and biogeochemical function in the northern Rocky Mountains
We have leveraged a 30 year long-term ecological monitoring (founded by MSU emeritus Professor Dr. Tad Weaver) site in a subalpine grassland in the Bangtail Mountains of SW Montana to experimentally understand how climate change and soil disturbance regimes have shaped the plant community structure and biogeochemical functioning of natural montane grassland ecosystems.
We are pursuing questions about how the frequency of soil disturbance alters grassland community succession and the associated effects on soil carbon storage and greenhouse gas fluxes. We are also interested in how climate perturbations have influenced community trajectories and biogeochemical processes.
The field site is located in the Bangtail Mountains northeast of Bozeman, MT.
Perennial grass agroecosystem C and N dynamics in semi-arid climates
An important but relatively unexplored question in western semi-arid bioenergy systems is whether the functional importance of regional crop selection dictates soil processes - namely, soil carbon sequestration and greenhouse gas emissions. This work aimed to increases our understanding of the biogeochemical implications and trade-offs of pairing alternative bioenergy crops and bio-fertilizers in western semi-arid agroecosystems. Specifically, we are examining shifts in carbon (C) and nitrogen (N) fluxes associated with experimental C4 and C3 perennial systems, switchgrass (P. virgatum), and tall-wheatgrass (T. ponticum), under conventional-synthetic (urea) and bio-fertilizer (cyanobacteria) based N-fertilizer treatments.
The field site was located at the Arthur H. Post Research Farm in Bozeman, Montana
We recently (2022) published this work in Global Change Biology: Bioenergy. Check out a short outreach clip that GCBB put together on youtube!