Abstract
Aims of study: Our aim is to check the effect of different environmental factors on the leaf senescence of four Quercus species with different leaf longevities, to help us better understand the implications of climate change on leaf demography.Area of study: The study was carried out in two sites of theprovince of Salamanca (central-westernSpain), both sites showing differences in their temperatures and soil water availability.Material and Methods: Over four years (2007-2010) we monitored the number of leaves of the different cohorts labelled on five specimens of each species at both sites to elaborate life-tables and calculate mortality rates. Mortality rates were then related to several other variables measured during the same period: air temperature, soil water availability, precipitation, predawn water potentials (Ypd) and leaf N resorption.Main results: In the two deciduous species maximum daily temperatures and the time during which their values remain above a certain threshold (between 11 and12ºC of maximum daily temperature) are the main factors controlling the timing of leaf abscission. In the evergreen species abscission of old leaves showed no relationship with the environmental factors analyzed. By contrast, mortality rates of old leaves were related to seasonal N resorption values, with the maximum mortality of old leaves coinciding in time with the maximum withdrawal of N from shed leaves and also with the emergence of the new leaf cohort.Research highlights: The increase in the duration of the leaves of the two deciduous species, as a result of the delayed senescence by warmer autumnal temperatures, could contribute to reducing the differences in the length of the productive leaf life with respect to the evergreen species. This could improve the competitive capacity of deciduous species as opposed to that of evergreen species, and thus alter their respective distribution patterns.Keywords: climate change; deciduous; evergreen; leaf abscission; temperature; water availability.
Highlights
Leaf phenology and longevity are traits linked to a large number of essential processes for plants and for the biosphere in general, making them priority objects of study in research in ecology
Some differences among the species under survey in this study were found regarding the effects of the different environmental factors on leaf senescence, which can have important repercussions on the total C assimilation of deciduous and perennial leaves in a new climatic scenario
In the two deciduous Quercus species, leaf death occurs in response to the decrease in temperature that accompanies the end of the growth season
Summary
Leaf phenology and longevity are traits linked to a large number of essential processes for plants and for the biosphere in general, making them priority objects of study in research in ecology. The patterns of emergence, abscission and leaf duration are governed by genetic factors, but they are affected by environmental ones, to which these patterns may be highly sensitive. This has led phenology to become an integral part of studies on climate change and its effects on the vegetation (Ibáñez et al, 2010; Chen & Xu, 2012; Clark et al, 2014). Most of the studies on the effect of environmental variables on phenology have focused on leaf emergence and its relationship with water availability and temperature. Water availability has shown contradictory results; while same authors have reported effects of increased precipitation on leaf emergence
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