Predicted Yield and Nutritive Value of an Alfalfa–Timothy Mixture under Climate Change and Elevated Atmospheric Carbon Dioxide

Abstract

Climate change studies have oft en focused on individual forage species although legume-grass mixtures are predominant on dairy farms in northern areas of North America. We assessed the eff ect of (i) future climate conditions (temperature and precipitation) and elevated atmospheric CO 2 concentration ([CO 2 ]), separately and together, on yield of alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.), grown alone or in mixture, and (ii) an adaptation strategy (timing and number of harvests) on future yield and nutritive value of an alfalfa-timothy mixture. Forage dry matter (DM) yield and nutritive value for two contrasting climate areas in eastern Canada were simulated with the Integrated Farm System Model over two future periods (2020-2049 and 2050-2079) using three climate models and two representative concentration pathways (RCP 4.5 and 8.5) of greenhouse gas emissions. Under projected future climate and without adaptation, annual forage yield of both species and the mixture increased in the colder area and decreased in the warmer area. In both areas, fi rst-cut yield increased due to faster growing degree-day accumulation, while regrowth yield decreased due to greater water and temperature stresses. Under elevated [CO 2 ], annual yield and the alfalfa percentage in the mixture increased. When combining climate change and elevated [CO 2 ], yield increased, except with the more drastic scenario (RCP 8.5, 2050(RCP 8.5, -2079 in the warmer area, and forage nutritive value was reduced. With adaptation, the mixture yield was increased from 5 to 35%, while nutritive value was generally maintained under all future scenarios, mostly because of additional cuts.

How can forage production in Nordic and Mediterranean Europe adapt to the challenges and opportunities arising from climate change?

“…Elevated atmospheric CO 2 concentration has the potential to increase photosynthetic rates and biomass production of C 3 plants (Ainsworth and Long, 2005;Soussana and Lüscher, 2007). In a study of timothy and lucerne mixtures in eastern Canada, which did take the effect of elevated CO 2 into account, 5-35% increase in DM yield in 2020-2079 relative to 1971-2000 was estimated (Thivierge et al, 2016). This occurred despite an increase in the duration of periods when high temperatures or water shortages limited the productivity.…”

Key challenges and priorities for modelling European grasslands under climate change

“…Limits to knowledge are therefore a constraint on model development in this research area. Current grass and crop models characterise plant growth responses to a range of environmental impacts, including changes in temperature, radiation, nitrogen and atmospheric CO 2 (Höglind et al, 2013;Wu et al, 2007) including impacts on forage nutritive value (Ben Touhami et al, 2013;Jégo et al, 2013;Jing et al, 2013;Thivierge et al, 2016). However, relatively few models incorporate all these aspects; some processes (such as the impacts of CO 2 and variation in N) may dealt with in a basic way, while some interactions are not fully understood (RamirezVillegas et al, 2015).…”

“…Recent models such as PaturaMata have been specifically developed in order to design management strategies for farms under climate change (Dusseux et al, 2015) and many current grassland models can be asked to respond to specific changes. Some process based farm scale models, such as the Integrated Farm Systems Model and some grassland models (Vuichard et al, 2007) are able to explore the impact of different management strategies (such as changes in cutting regimes) under climate change (Thivierge et al, 2016) but further development is required to improve the scope of adaptation options covered, and the characterisation of interactions between different strategies (Del Prado et al, 2013). Such development should take into account the need to explore the potential of more 'explorative' adaptation strategies (Martin et al, 2013) such as the introduction of silvo-pasture (Broom et al, 2013).…”

Optimal Regulation of the Balance between Productivity and Overwintering of Perennial Grasses in a Warmer Climate

“…Autumn-extended thermal growing seasons, combined with higher atmospheric CO 2 concentrations, have the potential to increase the productivity of perennial grasses in the autumn [6][7][8][9]. However, since the annual variation in temperature lags behind the annual variation in photoperiod, there is less light in autumn than at comparable temperatures in spring (Figure 1).…”

“…For example, in Finland, where the annual mean temperature has most likely increased by at least 2 • C during the last 150 years [3], the thermal growing season was predicted to become one to three months longer by the end of the century as compared to the period 1971-2000 [4]. Such extended growing seasons are expected to contribute to the increase in annual grassland yields in temperate climates [5][6][7][8][9]. Although the prediction models used so far account for drought limitations on growth, they do not account for possible effects of plant survival during seasonal stresses.…”