Effect of drought on biomass allocation in two invasive and two native grass species dominating the mixed‐grass prairie

Abstract

Control of exotic plant species invading the native prairie relies on our understanding of the eco‐physiological mechanisms responsible for the spread of these species as they compete with native plants for soil resources. We used a greenhouse pot experiment to study vegetative biomass allocation in response to drought stress in two exotic grass species, Kentucky bluegrass (Poa pratensis L.) and smooth brome (Bromus inermis Leyss), and two native species, western wheatgrass (Pascopyrum smithii (Rydb.) A. Löve) and green needlegrass (Stipa viridula Trin.). The experiment was conducted over 3 months in 2010 and again in 2011 in a factorial design of four species and two drought treatments. The proportional data of biomass allocation to shoots, roots, rhizomes and crowns (shoot base) of grass seedlings were analysed by both the nonparametric Mann–Whitney U‐test on the original data and one‐way anova on the arcsine‐transformed data. Our data suggest a clear distinction between the two invasive and two native species in potential competitiveness in soil resource use, with the two exotic species having higher biomass allocation to roots than the two native species and the native species having a higher biomass allocation to crowns than the two exotic species. It is interesting to note that the strongly rhizomatous smooth brome did not produce rhizomes in the first season's growth, regardless of the water stress level. The effect of drought stress on biomass allocation manifested itself more on rhizomes or crowns than on roots or shoots of the four studied grass species, with the effects species‐specific in nature.

Drought weakens the positive effects of defoliation on native rhizomatous grasses but enhances the drought‐tolerance traits of native caespitose grasses

“…Wang and Schellenberg () proposed that the aboveground and belowground biomass of P. smithii had a positive linear dependence, and both of them can be restricted by drought conditions due to its lower photosynthetic capacity and water efficiency in comparison with other grasses. In addition, we detected no significant difference in rhizome biomass of E. lanceolatus among all treatments, but water stress clearly reduced the rhizome biomass of P. smithii , because the strongly creeping rhizomes of P. smithii are more sensitive to drought stress than shoots and roots (Asay & Jensen, ; Dong et al., ). As expected, P. smithii and E. lanceolatus showed a greater compensation of shoot biomass after defoliation than Hesperostipa species, especially under well‐watered conditions, but no compensation of rhizome and root biomass was detected after defoliation.…”

OlderThinopyrum intermedium(Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants

“…We assumed values of 34ppm at 25 ºC for the photocompensation point (Γ*) based on the related species western wheatgrass ( Pascopyrum smithii; Dong et al , 2012 ), and values of 272ppm and 166 000ppm for K C and K O , respectively. Day respiration ( R D ) was fixed at 3.32mol m −2 s −1 at 25 ºC based on light–response curves taken in May 2013 (data not shown), and adjusted for temperature.…”

Growth indexes of Pennisetum purpureum cv. Roxo cultivated in different seasons under rainfed conditions

“…The reduction in LWR coincided with the end of rainfall at that time (Figure 1). Probably, the root system was configured as the main photoassimilate drain in order to increase the agronomic efficiency regarding the soil water absorption at deeper horizons (DONG et al, 2012).…”