Grassland species root response to drought: consequences for soil carbon and nitrogen availability

Abstract

Background and Aims Root traits are increasingly used to predict how plants modify soil processes. Here, we assessed how drought-induced changes in root systems of four common grassland species affected C and N availability in soil. We hypothesized that drought would promote resource-conservative root traits such as high root tissue density (RTD) and low specific root length (SRL), and that these changes would result in higher soil N availability through decreased root N uptake, but lower C availability through reduced root exudation. Methods We subjected individual plants to drought under controlled conditions, and compared the response of their root biomass, root traits, and soil C and N availability, to control individuals. Results Drought affected most root traits through reducing root biomass. Only SRL and RTD displayed plasticity; drought reduced SRL, and increased RTD in small plants but decreased RTD in larger plants.Reduced root biomass and a shift towards more resource-conservative root traits increased soil inorganic N availability but did not directly affect soil C availability. Conclusions These findings identify mechanisms through which drought-induced changes in root systems affect soil C and N availability, and contribute to our understanding of how root traits modify soil processes in a changing world.

Changes in root‐exudate‐induced respiration reveal a novel mechanism through which drought affects ecosystem carbon cycling

“…It is well known that drought can strongly affect plant growth and soil microbial community activity and composition, resulting in altered rates of C and N cycling processes (Gordon et al ., ; Sanaullah et al ., ; De Vries et al ., , ; de Nijs et al ., ). Similar to elevated CO 2 and grazing, root exudates have been hypothesized to play an important role in the response of soil microbial communities to drought, but it is challenging to disentangle root‐exudate‐mediated effects from other mechanisms through which drought affects soil microbial communities.…”

Grassland Phenology Response to Drought in the Canadian Prairies

“…Drought events have occurred more frequently worldwide in recent decades [8,9] and are predicted to be even more frequent and intense under multiple future climate scenarios [10,11]. Studies suggest that drought event properties (e.g., onset, end, and duration) have a substantial effect on grassland production and biomass [12][13][14][15][16], the stock of soil carbon and nitrogen [17][18][19], species composition [20][21][22][23], and spatial distribution of grass species [24]. However, the impact drought has on the key phenophases of the growing season of grasslands, including the start of growing season (SOG) (i.e., the onset of flowering or leaf out) in spring and the end of growing season (EOG) (i.e., the onset of senescence) in autumn, is not completely understood.…”

Root characteristic system improves drought tolerance in orchardgrass

“…Increasing forage yield and tolerance to abiotic stresses such as drought and cold are important objectives in most breeding programmes of orchardgrass (Sanada, Gras, & Van Santen, ). Water deficit not only decreases shoot growth rate, plant height and yield but also affects root growth (Vries, Brown, & Stevens, ). The root system of a crop acts as the “first line of defence” with respect to water stress (Fenta et al., ; Manavalan, Guttikonda, Nguyen, Shannon, & Nguyen, ).…”

“…The root system of a crop acts as the “first line of defence” with respect to water stress (Fenta et al., ; Manavalan, Guttikonda, Nguyen, Shannon, & Nguyen, ). Water stress can alter root system architecture and reduces the ability of roots to absorb water and nutrients from the soil (Vadez, ; Vries et al., ). An extensive root system enhances the uptake of water and nutrients and plays a major role in the ability of plants to tolerate drought stress (Gewin, ).…”

“…Vries et al. () found that water stress reduced root biomass, specific root length (RL), root tissue density and root dry matter content and increased root diameter in some forage grasses. In tall fescue ( Festuca arundinacea ), significant reduction in RL, root area (RA), root volume, root weight and root dry matter percentage is reported under water stress conditions (Pirnajmedin, Majidi, & Gheysari, , ).…”