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Contributed Talk

Session: : Physiological Ecology 4

COS 201-1 - The power of diversity: how mixing tree species can boost heat and drought tolerance

Wednesday, August 9, 2023
1:30 PM – 1:45 PM PDT
Location: E142
Abstract: High temperature, vapor pressure deficit (VPD), and drought stress alter plant water relations and hydraulics, with important consequences for the global carbon and water cycle. However, species interactions, such as resource partitioning or facilitation, can regulate water availability and reduce the adverse effects of drought and heat stress on trees. Yet, the underlying physiological mechanisms behind species interaction effects remain unclear. To date, few studies have investigated how the interactions between temperate trees influence their hydraulic responses to drought and heat, and even fewer have tried teasing apart the single vs. combined effects of heat and drought.

We experimentally assessed the single and combined effects of heat (+5°C) and drought (-50% irrigation) on leaf hydraulic traits (stomatal conductance, minimum conductance, leaf wilting tolerance, and leaf water potential) of two contrasting temperate tree species: Fagus sylvatica L. and Quercus pubescens Willd. Measurements were conducted for multiple years on young seedlings planted in intra-specific (i.e., monoculture) and inter-specific combinations (i.e., the two species together) in open-top chambers. We found that while drought decreased stomatal conductance and shifted leaf hydraulic trait trade-offs, high temperature acting alone had little impact on leaf hydraulics. Inter-specific interactions benefited Q. pubescens by allowing trees to maintain higher stomatal conductance and lower minimum conductance for the same degree of stress as monocultures. For F. sylvatica, neutral effects of species interactions were found, probably driven by the lower plasticity potential and higher vulnerability to drought.