Effects of precipitation change and neighboring plants on population dynamics of Bromus tectorum

Abstract

Shifting precipitation patterns resulting from global climate change will influence the success of invasive plant species. In the Front Range of Colorado, Bromus tectorum (cheatgrass) and other non-native winter annuals have invaded grassland communities and are becoming more abundant. As the global climate warms, more precipitation may fall as rain rather than snow in winter, and an increase in winter rain could benefit early-growing winter annuals, such as B. tectorum, to the detriment of native species. In this study we measured the effects of simulated changes in seasonal precipitation and presence of other plant species on population growth of B. tectorum in a grassland ecosystem near Boulder, Colorado, USA. We also performed elasticity analyses to identify life transitions that were most sensitive to precipitation differences. In both study years, population growth rates were highest for B. tectorum growing in treatments receiving supplemental winter precipitation and lowest for those receiving the summer drought treatment. Survival of seedlings to flowering and seed production contributed most to population growth in all treatments. Biomass of neighboring native plants was positively correlated with reduced population growth rates of B. tectorum. However, exotic plant biomass had no effect on population growth rates. This study demonstrates how interacting effects of climate change and presence of native plants can influence the population growth of an invasive species. Overall, our results suggest that B. tectorum will become more invasive in grasslands if the seasonality of precipitation shifts towards wetter winters and allows B. tectorum to grow when competition from native species is low.

The tortoise and the hare: reducing resource availability shifts competitive balance between plant species

“…It has been widely postulated that many invasive plants will benefit more than natives in the face of anthropogenic change due to broader ecological tolerances, greater plasticity, greater affinity for disturbance, and/or better trait matching to novel conditions (Dukes & Mooney 1999;Hellmann et al 2008;Thuiller, Richardson & Midgley 2008;Walther et al 2009;Davidson, Jennions & Nicotra 2011;Sandel & Dangremond 2012). Some evidence suggests that exotic species may outperform natives under high resource conditions, particularly when they exhibit high resource acquisitive traits, while natives may perform better when resources are scarce (Daehler 2003;Levine et al 2003; van Kleunen, Weber & Fischer 2010;Blumenthal et al 2013;Prev ey & Seastedt 2015;Concilio et al 2015). However, exotic responses to resource influxes can be quite conditional (Eskelinen & Harrison 2014), and exotics can outperform natives under low resource conditions when they bear more 'resource use efficient' strategies than the natives (Funk & Vitousek 2007).…”

Role of multiple invasion mechanisms and their interaction in regulating the population dynamics of an exotic tree

“…The direction of the effect depends on the context of the disturbance for both the focal exotic plant and the community it invades, including the disturbance history of the environment, the traits of the exotic plant, the season, frequency and duration of the disturbance (Crandall & Knight, ). Fewer studies have examined the role of competition with resident species (biotic resistance) in regulating population growth of exotic species, but those that have report that resident species may facilitate or compete with exotics (Crooks & Soulé, ; Griffith, ; Prevéy & Seastedt, ). Finally, studies examining the enemy release hypothesis have found significantly greater effects of herbivory on population growth rates of plants in their native compared to the invasive range (e.g.…”

“…Fewer studies have examined the role of competition with resident species (biotic resistance) in regulating population growth of exotic species, but those that have report that resident species may facilitate or compete with exotics (Crooks & Soulé, 1999;Griffith, 2010;Prevéy & Seastedt, 2015). Finally, studies examining the enemy release hypothesis have found significantly greater effects of herbivory on population growth rates of plants in their native compared to the invasive range (e.g.…”

A spring rainfall pulse causes greater in situ photosynthetic upregulation for Bromus tectorum compared to co-occurring native herbaceous species

“…The continued rapid spread of B. tectorum threatens to displace > 40% of the current area of sagebrush steppe in the next 30 years (Chambers et al, 2007 and references therein). Climate change is likely to facilitate B. tectorum expansion into higher elevations by increasing habitat suitability or altering competitive constraints, thereby favoring B. tectorum over native species (Compagnoni and Adler, 2014;Dukes and Mooney, 1999;Prevey and Seastedt, 2015). Management of B. tectorum requires better knowledge of its response to ephemeral soil water content during the growing season.…”