Stability of tallgrass prairie during a 19‐year increase in growing season precipitation

Abstract

Summary1. Precipitation is considered to be a key driver of ecosystem processes in mesic grasslands, and climate models predict changes in the amount and intensity of precipitation under future global change scenarios. Although most experimental rainfall studies decrease precipitation, seasonal rainfall is predicted to increase in the northern Great Plains under climate change. 2. We analysed changes in community composition and structure of upland and lowland native tallgrass prairie in central Kansas, USA, subjected to 19 years of irrigation designed to eliminate moisture stress throughout the growing season. 3. Irrigation had limited effects on species richness in both upland and lowland prairie. Total cover increased significantly and consistently with irrigation in drier uplands and in more mesic lowlands. Abundance of rhizomatous, tall, perennial species as well as C 3 forbs increased with irrigation. 4. The strongest response to irrigation came within the dominant functional type, C 4 perennial grasses. Panicum virgatum became the dominant species in irrigated lowlands, whereas Andropogon gerardii remained the dominant species in irrigated uplands and in control plots. Overall, irrigation had less effect on community composition and structure than other known drivers of grassland structure and function. 5. In comparison with other studies, our results demonstrate that water addition has less of an impact than fire, grazing or nitrogen addition on composition and dynamics in this mesic grassland. The strongest response to long-term irrigation occurred within the dominant functional type: tall, perennial, rhizomatous, C 4 grasses. Thus, functional redundancy will buffer this ecosystem from potential increases in rainfall due to climate change. Finally, our results highlight the limited utility of qualitative functional traits to predict how this mesic grassland will respond to climate change.

Resource colimitation governs plant community responses to altered precipitation

“…Whereas several previous studies have reported relatively high resistance to climatic changes in unproductive ecosystems (13,14,30,47,48), ours is among the first to identify resource colimitation as the mechanism responsible for this resistance.…”

Interactive effects of anthropogenic nitrogen enrichment and climate change on terrestrial and aquatic biodiversity

“…Research from Mediterranean systems (Zavaleta et al 2003a, c) and tall-grass prairie (Collins et al 2012) found that increased precipitation had a small positive or negligible effect, respectively, on species richness. Similar findings have been reported in China (Yang et al 2011a, b).…”

Global Environmental Change in Drylands: Ecohydrological Controls on Plant Communities

“…This is a novel finding because other studies in grasslands (Hsu et al, 2012) have shown that grasses alone have a negative response to increasing interannual rainfall variability in wet environments. Grasses typically have a high growth rate especially in wet environments (Teuling et al, 2010;Collins et al, 2012;Xu et al, 2015), consistent with the concept of the world-wide 'fast -slow' plant economics spectrum (Reich, 2014); thus, grasses could quickly take advantage of the window of opportunity existing in years with above average precipitation. The high growth rate in grasses increases fire frequency and fire-induced tree mortality (Bond et al, 2008;Ratajczak et al, 2014), thereby leading to a reduction in tree competition with grasses for soil water, which further favors grass biomass.…”

“…Fluctuations in resource/rainfall availability could provide windows of opportunity in resource enrichment and thus species (i.e., grasses) with a high growth rate may quickly take up resources, change the disturbance regime (i.e., fires), and then invade or dominate the landscape (e.g., Davis et al, Davis and Melissa, 2001;Corbin and D'Antonio, 2004). However, opposite interactions may occur in arid environments where grasses exhibit slow growth rates (e.g., Teuling et al, 2010;Collins et al, 2012). Indeed, recent field studies at the Jornada Basin (New Mexico) show that increasing interannual rainfall fluctuations could favor shrubs over grasses (e.g., Gherardi and Sala, 2015 a b).…”

“…Both of these models, however, ignored the roles of fires. Indeed, grasses typically have relatively high growth rates especially in wet environments (Teuling et al, 2010;Collins et al, 2012;Xu et al, 2015) and thus may more quickly take up soil water or other resources, thereby more effectively competing with trees in wet years. The competitive advantage of grasses in wet years could enhance fire occurrences, thereby increasing tree mortality (Bond et al, 2008;Ratajczak et al, 2014); as a result, the increase in interannual rainfall variability is expected to favor grasses at the expenses of trees.…”