Seminar - Stefano Manzoni
Date:
Thursday, October 15, 2015 14:00 - 16:00
Duration:
2 Hours
Categories:
Email
Speaker: Stefano Manzoni – Department of Physical Geography, Stockholm University
Title: Eco-hydrological optimality explains global patterns in plant hydraulic traits
Time & Place: Thursday 15th October 2015 14:00-15:00 Room KB3B3
Abstract: Plant hydraulic traits exhibit both trade-offs (e.g., xylem safety vs. efficiency) and coordination (e.g., correlation of liquid- and gas-phase conductances). While some of these patterns can be explained by physiological features at the conduit scale, here we present the hypothesis that trait coordination and trade-offs can emerge from eco-hydrological optimality criteria. In the short-term and in moist conditions, plants need to transport water fast to match the atmospheric evaporative demand, which causes a steep water potential gradient between leaves and soil. The larger this gradient, the higher the transpiration rate, until cavitation ensues and xylem hydraulic conductivity is decreased. Hence, there is a tradeoff between hydraulic efficiency and driving force, resulting in maximum transpiration rates at intermediate values of leaf water potential. Using a minimalist model of plant hydraulics, we show that maximum transpiration can be attained when saturated hydraulic conductivity and resistance to cavitation are inversely proportional (i.e., there is a xylem safety vs. efficiency trade-off), and that indeed maximum rates are reached across biomes. Plants also need to use soil water effectively when it becomes limiting. To do so, two strategies might be selected for: avoidance of hydraulic failure in dry periods and long-term maximization of transpiration rate (assumed as a proxy for plant fitness). Results show that both strategies require that stomatal closure is coordinated with loss of conductivity due to cavitation. Moreover, the optimal combinations of xylem and stomatal traits depend on both total rainfall and its distribution during the growing season. Drier conditions or intense rainfall events interspaced by prolonged dry spells favor plants with high resistance to cavitation and delayed stomatal closure as soils dry. In contrast, plants in mesic conditions benefit from cavitation prevention through earlier stomatal closure. The proposed eco-hydrological optimality criteria can be used as analytical tools to interpret variability in plant water use and predict trends in plant productivity and species composition under future climates.
Title: Eco-hydrological optimality explains global patterns in plant hydraulic traits
Time & Place: Thursday 15th October 2015 14:00-15:00 Room KB3B3
Abstract: Plant hydraulic traits exhibit both trade-offs (e.g., xylem safety vs. efficiency) and coordination (e.g., correlation of liquid- and gas-phase conductances). While some of these patterns can be explained by physiological features at the conduit scale, here we present the hypothesis that trait coordination and trade-offs can emerge from eco-hydrological optimality criteria. In the short-term and in moist conditions, plants need to transport water fast to match the atmospheric evaporative demand, which causes a steep water potential gradient between leaves and soil. The larger this gradient, the higher the transpiration rate, until cavitation ensues and xylem hydraulic conductivity is decreased. Hence, there is a tradeoff between hydraulic efficiency and driving force, resulting in maximum transpiration rates at intermediate values of leaf water potential. Using a minimalist model of plant hydraulics, we show that maximum transpiration can be attained when saturated hydraulic conductivity and resistance to cavitation are inversely proportional (i.e., there is a xylem safety vs. efficiency trade-off), and that indeed maximum rates are reached across biomes. Plants also need to use soil water effectively when it becomes limiting. To do so, two strategies might be selected for: avoidance of hydraulic failure in dry periods and long-term maximization of transpiration rate (assumed as a proxy for plant fitness). Results show that both strategies require that stomatal closure is coordinated with loss of conductivity due to cavitation. Moreover, the optimal combinations of xylem and stomatal traits depend on both total rainfall and its distribution during the growing season. Drier conditions or intense rainfall events interspaced by prolonged dry spells favor plants with high resistance to cavitation and delayed stomatal closure as soils dry. In contrast, plants in mesic conditions benefit from cavitation prevention through earlier stomatal closure. The proposed eco-hydrological optimality criteria can be used as analytical tools to interpret variability in plant water use and predict trends in plant productivity and species composition under future climates.