Life Sciences Commons^™

Do Early-Successional Weeds Facilitate Or Compete With Seedlings In Forest Restoration? Disentangling Abiotic Versus Biotic Factors, Mylen Arias, Rupesh R. Kariyat, Kimberly Wahl-Villarreal, Stephany Mendez, Jesus Chavana, Bradley O. Christoffersen

Biology Faculty Publications and Presentations

1. Semi-arid forests need cost-effective restoration strategies to address their severe degradation. Tree shelters are often used to minimize abiotic and biotic stress during seedling establishment. We asked if early-successional weeds act as a natural shelter by facilitating native seedlings, contingent on abiotic and biotic stressors and seedling ecological strategy.

2. We conducted a manipulative weed exclusion experiment at a semi-arid site in South Texas targeted for large-scale forest restoration to discern the net effect of weeds on the growth and survival of target thornscrub tree and shrub seedlings. We assessed the roles of contrasting seedling ecological strategies (fast vs. slow growth …

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Assessing Climate Change Impacts On Live Fuel Moisture And Wildfire Risk Using A Hydrodynamic Vegetation Model, Wu Ma, Lu Zhai, Alexandria Pivovaroff, Jacquelyn Shuman, Polly Buotte, Junyan Ding, Bradley O. Christoffersen, Ryan G. Knox, Max Moritz, Rosie A. Fisher

Biology Faculty Publications and Presentations

Live fuel moisture content (LFMC) plays a critical role in wildfire dynamics, but little is known about responses of LFMC to multivariate climate change, e.g., warming temperature, CO2 fertilization, and altered precipitation patterns, leading to a limited prediction ability of future wildfire risks. Here, we use a hydrodynamic demographic vegetation model to estimate LFMC dynamics of chaparral shrubs, a dominant vegetation type in fire-prone southern California. We parameterize the model based on observed shrub allometry and hydraulic traits and evaluate the model's accuracy through comparisons between observed and simulated LFMC of three plant functional types (PFTs) under current climate conditions. …

Hydraulic Architecture Explains Species Moisture Dependency But Not Mortality Rates Across A Tropical Rainfall Gradient, Alexandria L. Pivovaroff, Brett T. Wolfe, Nate G. Mcdowell, Bradley O. Christoffersen, Stuart J. Davies, L. Turin Dickman, Charlotte Grossiord, Riley T. Leff, Alistair Rogers, Shawn P. Serbin

Biology Faculty Publications and Presentations

Intensified droughts are affecting tropical forests across the globe. However, the underlying mechanisms of tree drought response and mortality are poorly understood. Hydraulic traits and especially hydraulic safety margins (HSMs), that is, the extent to which plants buffer themselves from thresholds of water stress, provide insights into species-specific drought vulnerability. We investigated hydraulic traits during an intense drought triggered by the 2015–2016 El Niño on 27 canopy tree species across three tropical forest sites with differing precipitation. We capitalized on the drought event as a time when plant water status might approach or exceed thresholds of water stress. We investigated …

Understanding Water And Energy Fluxes In The Amazonia: Lessons From An Observation-Model Intercomparison, Natalia Restrepo-Coupe, Loren P. Albert, Marcos Longo, Ian Baker, Naomi M. Levine, Lina M. Mercado, Alessandro C. Da Araujo, Bradley O. Christoffersen, Marcos H. Costa, David R. Fitzjarrald

Biology Faculty Publications and Presentations

Tropical forests are an important part of global water and energy cycles, but the mechanisms that drive seasonality of their land-atmosphere exchanges have proven challenging to capture in models. Here, we (1) report the seasonality of fluxes of latent heat (LE), sensible heat (H), and outgoing short and longwave radiation at four diverse tropical forest sites across Amazonia—along the equator from the Caxiuanã and Tapajós National Forests in the eastern Amazon to a forest near Manaus, and from the equatorial zone to the southern forest in Reserva Jaru; (2) investigate how vegetation and climate influence these fluxes; and …