Modelled effects of rising CO2 concentration and climate change on native perennial grass and sown grass-legume pastures

摘要

Native perennial grass and sown grass-legume pastures are an important agriculturaland environmental resource. We investigated the impact of rising carbon dioxide concentration([CO2]) and projected climate changes on these pasture ecosystems in southeastern Tasmania, Aus-tralia, using a biophysical simulation model, EcoMod. The model consists of interdependent modulesthat describe soil physicochemical and hydrological characteristics, and pasture growth and senes-cence, with fluxes described by empirical and mechanistic equations. Our simulations showed that innative pastures, projected climate change increased the biomass of C4 grasses, with limited impactupon C3 grasses, a trend reversed by rising [CO2]. In sown pastures, projected climate changedecreased the biomass of perennial rye grass Lolium perenne and total biomass markedly by 2070,whilst subterranean clover Trifolium subterraneum biomass increased. Subterranean clover biomasschanged little with increased [CO2] alone, whereas perennial rye grass biomass increased. Responsesacross pastures reflected species' tolerances to environmental factors, with projected climate changegenerally having more of an impact on biomass than rising [CO2]. Changes in both [CO2] and climateled to a reduction in protein content and digestibility. Soil inorganic nutrient concentrationsdecreased with increasing [CO2] and increased with projected climate change. Further simulationsshould investigate whether these patterns are robust for different sites and alternative environmen-tal futures. Our results reinforce the need to pursue adaptation strategies in response to environ-mental change in order to maintain productive pasture ecosystems.