Biology Commons^™

The Effects Of Cheatgrass Invasion On Us Great Basin Carbon Storage Depend On Interactions Between Plant Community Composition, Precipitation Seasonality, And Soil Climate Regime, Toby M. Maxwell, Matthew J. Germino

Biology Faculty Publications and Presentations

1. Annual-grass invasions are transforming desert ecosystems in ways that affect ecosystem carbon (C) balance, but previous studies do not agree on the pattern, magnitude and direction of changes. A recent meta-analysis of 41 articles and 386 sites concludes that invasion by annual grasses such as cheatgrass (Bromus tectorum L) reduces C in biomass across the Great Basin (Nagy et al., 2021). Reanalysis reveals that whether cheatgrass affects biomass C stocks is not generalizable, but rather depends on the considerable variation in climate across the subject sites. Our analysis suggests that accurate Great Basin-scale estimates of cheatgrass effects on C …

Bayesian Inference Of Hydraulic Properties In And Around A White Fir Using A Process-Based Ecohydrologic Model, Elias C. Massoud, A. J. Purdy, Bradley O. Christoffersen, L. S. Santiago, C. Xu

Biology Faculty Publications and Presentations

We present a parameter estimation study of the Soil-Tree-Atmosphere Continuum (STAC) model, a process-based model that simulates water flow through an individual tree and its surrounding root zone. Parameters are estimated to optimize the model fit to observations of sap flux, stem water potential, and soil water storage made for a white fir (Abies concolor) in the Sierra Nevada, California. Bayesian inference is applied with a likelihood function that considers temporal correlation of the model errors. Key vegetation properties are estimated, such as the tree's root distribution, tolerance to drought, and hydraulic conductivity and retention functions. We find …

Individual-Based Modeling Of Amazon Forests Suggests That Climate Controls Productivity While Traits Control Demography, Sophie Fauset, Manuel Gloor, Nikolaos M. Fyllas, Oliver L. Phillips, Gregory P. Asner, Timothy R. Baker, Lisa Patrick Bentley, Roel J. W. Brienen, Bradley O. Christoffersen, John Del Aguila-Pasquel

Biology Faculty Publications and Presentations

Climate, species composition, and soils are thought to control carbon cycling and forest structure in Amazonian forests. Here, we add a demographics scheme (tree recruitment, growth, and mortality) to a recently developed non-demographic model—the Trait-based Forest Simulator (TFS)—to explore the roles of climate and plant traits in controlling forest productivity and structure. We compared two sites with differing climates (seasonal vs. aseasonal precipitation) and plant traits. Through an initial validation simulation, we assessed whether the model converges on observed forest properties (productivity, demographic and structural variables) using datasets of functional traits, structure, and climate to model the carbon cycle at …