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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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The functional connectivity network of wintering gulls links seven habitat types, acting ricefields as the central node

The functional connectivity network of wintering gulls links seven habitat types, acting ricefields as the central node

The lesser black-backed gull is now the second most abundant wintering waterbird in Andalusian wetlands. Many birds are fitted with GPS loggers on their breeding grounds in northern Europe, and using 42 tagged individuals we studied the connectivity network between different sites and habitats in Andalusia. Thirty seven principal sites (nodes) from seven different habitats (ricefields, landfills, natural lakes, reservoirs, fish ponds, coastal marshes and ports) were identified. By analysing nearly 6,000 gull flights, it was found that Doñana ricefields are the most important node in the network, but that 90% of flights are made between a wetland and a landfill. The 37 nodes are split into 10 functional units (modules) in which gulls tend to fly daily and up to 60 km between a wetland roost site, and a landfill feeding site. This network allows to predict how gulls contribute to seed dispersal, wetland eutrophication, and the spread of pathogens such as antibiotic resistant bacteria. informacion[at] Martín-Vélez et al (2019) Functional connectivity network between terrestrial and aquatic habitats by a generalist waterbird, and implications for biovectoring. Science Total Environm 107: 135886 DOI 10.1016/j.scitotenv.2019.135886