Description
We reviewed the literature to assess the effect of climate change factors on forage legumes. Whether growing in monoculture or mixtures with grasses, exposing legumes to elevated CO2 (eCO2) generally leads to sustained increases in forage accumulation (FA) and N fixation, but elevated temperature (eT) in conjunction with eCO2 usually reduces magnitude of these responses. In legumes, nodules represent large C sinks, precluding photosynthetic acclimation to eCO2 observed in non-N fixing plants. Greater N fixation in legume-grass mixtures exposed to eCO2 is due to greater percentage of legume N derived from symbiotic fixation and often an increase in legume proportion in mixtures. Herbage nutritive value (NV) responses to eCO2 are less pronounced than FA, but lesser herbage N and greater non-structural carbohydrate (NSC) concentrations are common with eCO2. Drought effects on legume NV are inconsistent, but eT usually decreases NV. Data from one legume species suggest eCO2 and eT negatively affect pollen grain morphology and viability, but they increase flower number and nectar sugar concentration. Under eT, flowers opened earlier in the day causing earlier pollinator visits, but when combined with water stress, eT reduced pollinator visits. Though there is variation in the literature for some responses, we conclude that eCO2 generally increases legume FA, N fixation, and tissue NSC concentration, while reducing herbage N concentration. Drought reduces FA, but drought effects on NV are not consistent. Elevated temperature has a negative effect on legume NV, and, when combined with eCO2, can reduce the magnitude of the positive FA and N fixation response to eCO2. Climate change factors can affect legume pollen viability and pollinator behavior, potentially influencing plant reproductive success. Overall, effects of climate change factors on forage legumes can be generalized, but interactions among change factors and site-specific soil and climate conditions may cause variation from expected responses.
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Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Climate Change and Legume Performance in Grassland Agroecosystems
We reviewed the literature to assess the effect of climate change factors on forage legumes. Whether growing in monoculture or mixtures with grasses, exposing legumes to elevated CO2 (eCO2) generally leads to sustained increases in forage accumulation (FA) and N fixation, but elevated temperature (eT) in conjunction with eCO2 usually reduces magnitude of these responses. In legumes, nodules represent large C sinks, precluding photosynthetic acclimation to eCO2 observed in non-N fixing plants. Greater N fixation in legume-grass mixtures exposed to eCO2 is due to greater percentage of legume N derived from symbiotic fixation and often an increase in legume proportion in mixtures. Herbage nutritive value (NV) responses to eCO2 are less pronounced than FA, but lesser herbage N and greater non-structural carbohydrate (NSC) concentrations are common with eCO2. Drought effects on legume NV are inconsistent, but eT usually decreases NV. Data from one legume species suggest eCO2 and eT negatively affect pollen grain morphology and viability, but they increase flower number and nectar sugar concentration. Under eT, flowers opened earlier in the day causing earlier pollinator visits, but when combined with water stress, eT reduced pollinator visits. Though there is variation in the literature for some responses, we conclude that eCO2 generally increases legume FA, N fixation, and tissue NSC concentration, while reducing herbage N concentration. Drought reduces FA, but drought effects on NV are not consistent. Elevated temperature has a negative effect on legume NV, and, when combined with eCO2, can reduce the magnitude of the positive FA and N fixation response to eCO2. Climate change factors can affect legume pollen viability and pollinator behavior, potentially influencing plant reproductive success. Overall, effects of climate change factors on forage legumes can be generalized, but interactions among change factors and site-specific soil and climate conditions may cause variation from expected responses.
