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Morpho-functional traits and plant response to drought conditions in seedlings of six native species of Ecuadorian Ecosystems

Abstract:

Tropical Andean ecosystems have been identified as very vulnerable to climate change. Changes in climatic conditions, especially drought as envisaged by climate change projections, could affect the establishment of new individuals that are responsible for ensuring the persistence of species and plant communities. The aim was to study the main morpho-functional traits related to water use and drought resistance of native plant species from Ecuadorian ecosystems during imposed drought periods. Seedlings of six native species representative of the Ecuadorian Andes were studied: lower montane evergreen forest (Alnus acuminata and Cedrela montana), montane cloud forest (Podocarpus sprucei and Aegiphila ferruginea) and montane dry shrubland (Schinus molle and Caesalpinia spinosa). Morphological characterisation, a root growth capacity test and stomatal conductance measurements during two controlled drought periods were used to investigate biomass allocation patterns, the root system morphology and gas exchange patterns of species, respectively. The main results indicated that species-specific differences in morpho-functional traits and allocation patterns determined responses to water availability and drought conditions. Low relative growth rate, leaf area ratio and specific leaf area, and high specific root length, were related to drought-resistant species as P. sprucei and C. spinosa. In contrast, a high or moderate relative growth rate, leaf area and root biomass, but low specific root length as in A. ferruginea, S. molle, C. montana, were related to lower resistance to drought conditions. Despite A. acuminata showed high specific root length, it was reported as a species sensitive to drought. Overall, patterns of stomatal conductance, linked to biomass allocation patterns and root system morphology, especially specific root length, seemed to be related to differences in vulnerability to drought in these species. Drought response was independent of species habitats. Unexpectedly, P. sprucei, belonging to montane cloud forest showed higher drought resistance than S. molle, belonging to montane dry shrubland.