Drought is a stronger driver of plant morphology and nutritional composition than warming in two common pasture species

Abstract

Under warmer and drier future conditions, global livestock and dairy production are threatened by impacts on the productivity and nutritional quality of pastures. However, morphological and nutritional adjustments within plants in response to warming and drought vary among species and less is known how these relate to production and forage quality. To investigate this, we grew two common pasture species, tall fescue (Festuca arundinacea: grass) and lucerne (Medicago sativa: legume), in a climate-controlled facility, under different temperatures (ambient and elevated) and watering regimes (well-watered and droughted). We found that drought had a strong negative impact on biomass production, morphology and nutritional quality while warming only significantly affected both species when response metrics were considered in concert, although to a lesser degree than the drought. Furthermore, interactions between warming and drought were only seen for lucerne, with the greatest reduction in biomass and most dead material and dry matter content. In tall fescue, drought had bigger impacts on nutritional composition than morphological traits, while in lucerne, drought affected all morphological traits and most nutritional parameters. These findings suggest that in future climate scenarios, drought may be a stronger driver of changes in the morphology and nutritional composition of pasture grasses and legumes, compared to modest levels of warming.

Near-infrared spectroscopy calibration strategies to predict multiple nutritional parameters of pasture species from different functional groups

“…This may reflect the fact that as well as comprising a broad range of functional diversity and species origins, our plants were also grown under very varied environmental conditions, including control conditions as well as warming and severe droughts, imposed individually and in combination. Warming treatments included continuous + 3°C above-canopy temperature (field experiment; Churchill et al, 2020) and + 4°C above ambient (glasshouse experiment; Catunda et al, 2021;Zhang et al, 2021). Drought treatments consisted of winter and spring periods of 60% rainfall reduction (field experiment), and 60% soil water holding capacity reduction (glasshouse experiment).…”

“…It is The copyright holder for this preprint this version posted August 1, 2021. field), Catunda et al (2021;glasshouse) and Zhang et al (2021;glasshouse).…”

“…High quality, accurate NIRS calibrations are an essential tool to help rapidly track/monitor forage quality changes in response to management interventions and climate conditions, consequently improving pasture management practice in the future. field), Catunda et al (2021;glasshouse) and Zhang et al (2021;glasshouse).…”

“…In a companion study using a glasshouse facility, two of the species from the field site (Festuca arundinacea and Medicago sativa) were grown using field soil. A detailed overview of the experimental facilities descriptions and pasture management are reported in Churchill et al (2020;field), Catunda et al (2021;glasshouse), and Zhang et al (2021;glasshouse). The ten different pasture species used in this study include a range of plant functional groups (C3 legumes; C3/C4 grasses; annuals and perennials) and origins (tropical and temperate; introduced and native) and are commonly used as forage in grasslands in south-eastern Australia and, with the exception of the grass Rytidosperma caespitosum, internationally (Table 1).…”

“…The ten different pasture species used in this study include a range of plant functional groups (C3 legumes; C3/C4 grasses; annuals and perennials) and origins (tropical and temperate; introduced and native) and are commonly used as forage in grasslands in south-eastern Australia and, with the exception of the grass Rytidosperma caespitosum, internationally (Table 1). Plants were grown under a wide range of environmental conditions, including warming and/or drought treatments; (Churchill et al, 2020;Catunda et al, 2021), while other conditions were held constant (soils, fertilization, pests, etc.). These experimentally manipulated conditions maximised the range of variation in the concentrations of chemical components .…”