The trade-off between cold resistance and growth determines the <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> treeline |
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Authors: | Marco A Molina-Montenegro Jorge Gallardo-Cerda T S M Flores Cristian Atala |
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Institution: | 1.Centro de Estudios Avanzado en Zonas áridas (CEAZA),Universidad Católica del Norte,Coquimbo,Chile;2.Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas,Universidad de Concepción,Concepción,Chile;3.Departamento de Ciencia y Tecnología Vegetal,Campus Los ángeles, Universidad de Concepción,Concepción,Chile |
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Abstract: | The upper and poleward limit of tree distribution are usually determined by abiotic factors such as low temperature and strong
winds. Thus, cold resistance is a key element for survival in high altitudes and latitudes where conditions can reduce plant
growth. A trade-off between resource allocation to cold resistance and growth could emerge in populations frequently exposed
to low temperatures like those in the treeline zone. We studied annual height growth and ice nucleation temperature in Nothofagus pumilio (Nothofagaceae) populations growing in its extremes of altitudinal distribution and in 3 sites situated on a latitudinal
gradient in the Chilean Andes. Additionally, gas exchange, water and nitrogen use efficiency and total soluble sugar (TSS)
were also measured as possible mechanisms for survival in high altitudes. Individuals from the treeline populations showed
lower annual height growth and lower ice nucleation temperatures compared with those from lower populations. In the same way,
individuals from more poleward populations showed lower annual height growth and lower ice nucleation temperatures. Gas exchange,
water and nitrogen use efficiency and TSS were also higher in the high altitude populations. The results obtained support
the hypothesis of trade-off, because the upper and poleward populations showed more cold resistance but a lower height growth.
Additionally, we show that cold resistance mechanisms do not impact the physiological performance, suggesting possible adaptation
of the high altitude populations. Low temperatures may be affecting cellular growth instead of photosynthesis, creating a
pool of carbohydrates that could participate in cold tolerance. Other abiotic and biotic factors should be also assessed to
fully understand the distributional range of Nothofagus species. |
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