Precipitation pulse use by an invasive woody legume: the role of soil texture and pulse size

Abstract

Plant metabolic activity in arid and semi-arid environments is largely tied to episodic precipitation events or "pulses". The ability of plants to take up and utilize rain pulses during the growing season in these water-limited ecosystems is determined in part by pulse timing, intensity and amount, and by hydrological properties of the soil that translate precipitation into plant-available soil moisture. We assessed the sensitivity of an invasive woody plant, velvet mesquite (Prosopis velutina Woot.), to large (35 mm) and small (10 mm) isotopically labeled irrigation pulses on two contrasting soil textures (sandy-loam vs. loamy-clay) in semi-desert grassland in southeastern Arizona, USA. Predawn leaf water potential (psi(pd)), the isotopic abundance of deuterium in stem water (deltaD), the abundance of 13C in soluble leaf sugar (delta13C), and percent volumetric soil water content (theta(v)) were measured prior to irrigation and repeatedly for 2 weeks following irrigation. Plant water potential and the percent of pulse water present in the stem xylem indicated that although mesquite trees on both coarse- and fine-textured soils quickly responded to the large irrigation pulse, the magnitude and duration of this response substantially differed between soil textures. After reaching a maximum 4 days after the irrigation, the fraction of pulse water in stem xylem decreased more rapidly on the loamy-clay soil than the sandy-loam soil. Similarly, on both soil textures mesquite significantly responded to the 10-mm pulse. However, the magnitude of this response was substantially greater for mesquite on the sandy-loam soil compared to loamy-clay soil. The relationship between psi(pd) and delta13C of leaf-soluble carbohydrates over the pulse period did not differ between plants at the two sites, indicating that differences in photosynthetic response of mesquite trees to the moisture pulses was a function of soil water availability within the rooting zone rather than differences in plant biochemical or physiological constraints. Patterns of resource acquisition by mesquite during the dynamic wetting-drying cycle following rainfall pulses is controlled by a complex interaction between pulse size and soil hydraulic properties. A better understanding of how this interaction affects plant water availability and photosynthetic response is needed to predict how grassland structure and function will respond to climate change.

Impacts of extreme precipitation and seasonal changes in precipitation on plants

“…Many field experiments have imposed drought (Hanson et al, 2003;Wullschleger and Hanson, 2006;Beier et al, 2012) or described the impact of pulses of precipitation (Fravolini et al, 2005;Potts et al, 2006;Zeppel et al, 2008a;Resco et al, 2009). Here, we focus on seasonal changes in precipitation and extreme precipitation.…”

A Geo‐spatial study for analysing temporal responses of NDVI to rainfall

“…Rainfall is a key factor that controls dynamic changes in vegetation growth in arid and semi-arid regions as vegetation cover in those regions are extremely susceptible to the quantity, duration and frequency of rainfall (Fravolini et al, 2005;Liu et al, 2012;Gamon et al, 2013;Dutta et al, 2015;Kundu et al, 2015c). Past studies revealed that fluctuation of NDVI in drylands is consistent with spatial and temporal variations in rainfall (Fabricante et al, 2009;Kundu & Dutta, 2011;Kundu et al, 2015aKundu et al, ,b, 2016Kundu et al, , 2017.…”

Woody Plant Encroachment: Causes and Consequences

“…In lightly grazed, high-productivity grasslands, grasses will initially be taller than woody plant seedlings, reducing light availability (de Dios et al 2014). Typically, grasses and woody seedlings in waterlimited environments share the same shallow soil horizon , so that grasses may furthermore monopolize soil resources to near exclusion of woody plant recruits, especially under environmental conditions that favor grasses: fine-texture or shallow soil sites with a summer rainy season characterized by small rainfall events that wet only the near-surface soils (Fravolini et al 2005). However, grazing reduces grass leaf area, root density, and depth and therefore competitive effects on seedlings above and below ground.…”

“…Many woody species have both a shallow, laterally extensive root system and deep taproots (Schenk and Jackson 2002). This reflects a generalist strategy for soil resource capture that allows them to use small rainfall events and the nutrients concentrated in the upper soil layers (Fravolini et al 2005), but to also access water and nutrients (e.g., NO 3 − ) percolated below the depths effectively exploited by grasses. Woody plants with this dimorphic root system can therefore exploit a wide range of growing season conditions (Scott et al 2006;Priyadarshini et al 2015).…”