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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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Effect of habitat quality on flying patterns of the butterfly Plebejus argus

Effect of habitat quality on flying patterns of the butterfly Plebejus argus

Animal movement often changes with habitat quality. Butterfly movements may be influenced by structural attributes of habitat patches or may reflect the distribution of food, mates, host plants or ecological interactions. The relative influence of structural and functional factors on flight patterns is poorly understood, partly because butterfly movements are often described by simplified representations of actual trajectories. Using high-resolution GPS tracking accurate trajectories of routine movements of Plebejus argus were obtained in a heterogeneous natural landscape. Habitat quality in patches was ranked according to the abundance of host and nectar plants as well as the abundance of nests of its mutualistic ant Lasius niger. Movements were slow and winding in high quality habitats whereas faster, straighter flights were observed in poor habitats. At edges, butterflies often crossed without any exploratory behaviour towards patches of better quality, suggesting they may use cues to detect resources at some distance. Conversely, individuals usually stayed in the patch after exploring edges with other patches of lower quality. However, scanning also preceded exits towards clearly unsuitable habitat, compatible with transfers to distant high-quality patches. Authors conclude that patterns of movement in P. argus were explained by spatial heterogeneity defined by functional rather than structural criteria. It is also show that inexpensive handheld GPS receivers allow depicting detailed flying trajectories in open flat terrain revealing complex behavioural patterns. informacion[at] Fernández et al (2016) Fine scale movements of the butterfly Plebejus argus in a heterogeneous natural landscape as revealed by GPS tracking. J Insect Behav 29:80–98 DOI 10.1007/s10905-016-9543-7