Climate effect on the growth and hydraulic traits of two shrubs from the top of a Mediterranean mountain

Abstract

Increasing mean global temperatures in conjunction with increases in the frequency and severity of drought events affect plant growth and physiology, particularly in more arid and mountainous ecosystems. Thus, it is imperative to understand the response of plant growth to climatic oscillations in these regions. This study used dendrochronological and wood anatomical traits of two shrub species growing over 1500 m.a.s.l. in the Serra da Estrela (Portugal), Juniperus communis and Cytisus oromediterraneus, to analyze their response to temperature and water availability parameters. Results showed an increase in shrub growth related to the increase over time of the mean minimum and maximum monthly temperature in Serra da Estrela. Warming seems to promote shrub growth because it lengthens the growing season, although J. communis responds mainly to spring maximum temperature while C. oromediterraneus is influenced by fall maximum temperature. Hydraulic traits of J. communis and C. oromediterraneus were negatively influenced by winter drought. Additionally, there were species-specific differences in response to changes in water availability. J. communis radial growth was significantly affected by spring drought conditions, while C. oromediterraneus radial growth was significantly affected by spring precipitation. C. oromediterraneus hydraulic traits were also significantly affected by drought conditions from the previous spring and fall. This study shed light on specific differences in the response to climate between two co-occurring shrub species in the top of an understudied Mediterranean mountain, which could have implications in the future distribution of woody species within this region.