Abstract
Drought is a major factor limiting tree growth and plant vitality. In the Mediterranean region, the length and intensity of drought stress strongly varies with altitude and site conditions. We used electronic dendrometers to analyze the response of two native pine species to drought and precipitation events. The five study sites were located along an elevation gradient on the Mediterranean island of Corsica (France). Positive stem increment in the raw dendrometer measurements was separated into radial stem growth and stem swelling/shrinkage in order to determine which part of the trees’ response to climate signals can be attributed to growth. Precipitation events of at least 5 mm and dry periods of at least seven consecutive days without precipitation were determined over a period of two years. Seasonal dynamics of stem circumference changes were highly variable among the five study sites. At higher elevations, seasonal tree growth showed patterns characteristic for cold environments, while low-elevation sites showed bimodal growth patterns characteristic of drought prone areas. The response to precipitation events was uniform and occurred within the first six hours after the beginning of a precipitation event. The majority of stem circumference increases were caused by radial growth, not by stem swelling due to water uptake. Growth-induced stem circumference increase occurred at three of the five sites even during dry periods, which could be attributed to stored water reserves within the trees or the soils. Trees at sites with soils of low water-holding capacity were most vulnerable to dry periods.
Highlights
Water availability is the most limiting abiotic factor for plant growth and productivity, especially in arid or semi-arid environments [1,2]
In contrast to other studies, we investigated the response to climate events during dry periods, and to precipitation events
We investigated the response of two pine species, which are widespread over the Mediterranean basin, i.e., Pinus pinaster Aiton growing at low to middle elevations, and Pinus nigra J.F
Summary
Water availability is the most limiting abiotic factor for plant growth and productivity, especially in arid or semi-arid environments [1,2]. Depending on the rooting and soil depth, trees can have access to different soil water layers and may respond differently to single precipitation events [8,9,10]. Several studies underline the importance of winter precipitation in summer-dry climates, which may stimulate an entirely different plant response than a summer rain event as shown for shrubs in desert environments [11,12]. This is the case in climates where deeper soil water reservoirs are replenished by winter precipitation [9]
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