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Strategies shrubby junipers adopt to tolerate drought differ by site

Drought-induced dieback episodes are globally reported among forest ecosystems but they have been understudied in scrublands. Chronically-stressed individuals are supposed to be more vulnerable prior to drought which triggers death. Drought-triggered dieback and mortality events affecting Mediterranean Juniperus phoenicea scrublands were analyzed in two sites with contrasting climate and soil conditions located in Spain. The radial growth patterns of coexisting living and dead junipers, including the calculation of growth statistics used as early-warning signals, quantified growth response to climate, were characterized and the wood C and O isotope discrimination was analyzed. In the inland, continental site with rocky substrates (Yaso, Huesca, N Spain), dead junipers grew less than living junipers about three decades prior to the dieback started in 2016. However, in the coastal, mild site with sandy soils (Doñana, Huelva, SW Spain), dead junipers were smaller but grew more than living junipers about two decades before the dieback onset in 2005. The only common patterns between sites were the higher growth coherence in both living and dead junipers prior to the dieback, and the decrease in growth persistence of dead junipers. Cool and wet conditions in the prior winter and current spring, and cool summer conditions enhanced juniper growth. In Doñana, growth of living individuals was more reduced by warm July conditions than in the case of dead individuals. Higher ?13C values in Yaso indicate also more pronounced drought stress. In Yaso, dead junipers presented lower ?18O values, but the opposite occurred in Doñana suggesting different changes in stomatal conductance prior to death. Warm summer conditions enhance evapotranspiration rates and trigger dieback in this shallow-rooted species, particularly in sites with a poor water-holding capacity. Chronic, slow growth is not always a reliable predictor of drought-triggered mortality. informacion[at] Camarero et al (2020) Dieback and mortality of junipers caused by drought: Dissimilar growth and wood isotope patterns preceding shrub death. Agr Forest Meteorol 291, 108078. DOI 10.1016/j.agrformet.2020.108078
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High livestock numbers have a negative influence on Canarian Egyptian vultures’ body condition

High livestock numbers have a negative influence on Canarian Egyptian vultures' body condition

Individual traits such as body mass can serve as early warning signals of changes in the fitness prospects of animal populations facing environmental impacts. Here, taking advantage of a 19?year monitoring, the question how individual, population and environmental factors modulate long?term changes in the body mass of Canarian Egyptian vultures was addressed. Individual vulture body mass increased when primary productivity was highly variable, but decreased in years with a high abundance of livestock. The hypothesis tested was that carcasses of wild animals, a natural food resource that can be essential for avian scavengers, could be more abundant in periods of weather instability (i.e. variation in primary productivity) but depleted when high livestock numbers lead to over?grazing. Results would also indicate that wild prey represents essential, but highly underestimated, resources, whose availability would affect vulture condition and fitness. In addition, increasing vulture population numbers also negatively affect body mass suggesting density?dependent competition for food. Interestingly, the relative strength of individual, population and resource availability factors on body mass changed with age and territorial status, a pattern presumably shaped by differences in competitive abilities and/or age?dependent environmental knowledge and foraging skills. This study supports that individual plastic traits may be extremely reliable tools to better understand the response of secondary consumers to current and future natural and human?induced environmental changes. Disentangling the complex relationships among ecosystem-level factors, population structure, and individual characteristics that determine animal body condition will help define management strategies for this and other ecologically similar endangered populations. informacion[at] Donázar et al (2020) Too much is bad: increasing numbers of livestock and conspecifics reduce body mass in an avian scavenger. Ecol Appl DOI 10.1002/eap.2125