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Plant Focus

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A guest post by Matt Candeias, host of the In Defense of Plants podcast and blog

Functional Diversification in the “Roburoid” and “Cerris” Oaks

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J.A. Ramírez-Valiente, R. López, and I. Aranda

Published May 2019 in International Oaks No. 30: 117–124

Abstract

Climate is a critical factor of selection for forest tree species. Disentangling the functional mechanisms underlying climate adaptation is essential to understand current species distributions and predict future patterns under changing climatic conditions. In this study, we assessed whether drought resistance and growth potential have evolved as a result of climate adaptation in European/North African oaks (Quercus spp.), and explored a potential trade-off between functional strategies. Our hypothesis is that oaks have evolved towards increasing resistance to water deficit at the southern range as a result of selective pressures imposed by summer drought whereas a selection towards increasing growth potential has occurred in high productive areas of central Europe characterized by mesic summers. To test this hypothesis, we conducted a greenhouse experiment where seedlings originating from 11 oak species were subjected to contrasting watering regimes. Our study revealed differences among oak species in traits related to growth and drought resistance. On average, species originating from climates with more severe dry seasons exhibited more sclerophyllous leaves with lower specific leaf area, mass-based photosynthetic rates and relative growth rates at the beginning of the growing season. Importantly, xeric species had higher growth rates at the end of the growing season and lower native embolism. A trade-off was observed between mass-based photosynthetic rates and native loss of hydraulic conductivity across treatments, indicating that species with higher growth potential are more vulnerable to xylem cavitation. Overall, our results showed that functional strategies are associated with the climate of origin in European/North African oaks.

Keywords

drought tolerance, climate adaptation, functional strategies, trade-offs

References

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