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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]ebd.csic.es: 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


https://www.sciencedirect.com/science/article/pii/S0168192320301805?dgcid=author#ack0001
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Firebreaks constrain butterfly movements

Firebreaks constrain butterfly movements

Firebreaks are linear strips that dissect the landscape and prevent or mitigate the spread of wildfires in Mediterranean landscapes. However, few studies have addressed their potential effect on insect behavior. The lack of traffic and other human activities in firebreaks makes them suitable for testing the sole effect of physical habitat disruption on animal movement. Main objective was to evaluate whether the pattern of movement by a butterfly species was affected by this landscape element. Flight trajectories of the lycaenid butterfly Plebejus argus were reconstructed within and around one firebreak using visual and GPS tracking in Doñana National Park (southern Spain). Butterflies that were active at the firebreak boundary often refused to enter the firebreak and, when they did, most individuals returned before reaching the opposite side. Inside the firebreak faster and straighter trajectories were recorded than in adjacent scrubland areas. Butterflies that crossed the firebreak headed the most favorable direction to minimize the time spent within the habitat discontinuity. At the landscape scale, firebreak density increased in areas where P. argus habitat was more fragmented and had lower quality. In other studies, when firebreaks are mowed instead of ploughed, they appeared to be beneficial for butterflies. In contrast, in Doñana, barren firebreaks do not provide any valuable resource for P. argus and its environmental conditions probably entail considerable physiological stress. In sum, a narrow, open linear element lacking any human activity induces a marked change in the movement behavior of a butterfly species, with potential consequences on population dynamics at the landscape scale. Therefore, firebreaks used for protecting Mediterranean landscapes could have side effects on animal populations other than localized habitat loss due to mere vegetation removal. informacion[at]ebd.csic.es: Fernández et al (2019) Firebreaks as a barrier to movement: the case of a butterfly in a Mediterranean landscape. J Insect Conserv DOI 10.1007/s10841-019-00175-5


https://link.springer.com/article/10.1007%2Fs10841-019-00175-5#Abs1