Greater sensitivity to hotter droughts underlies juniper dieback and mortality in Mediterranean shrublands.,Science of the Total Environment

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Greater sensitivity to hotter droughts underlies juniper dieback and mortality in Mediterranean shrublands.
Science of the Total Environment ( IF 8.2 ) Pub Date : 2020-02-26 , DOI: 10.1016/j.scitotenv.2020.137599
Raúl Sánchez-Salguero ₁ , J Julio Camarero ₂

Affiliation

Drought-induced dieback episodes have been globally reported. However, few studies have jointly examined the role played by drought on growth of co-occurring shrub and tree species showing different dieback and mortality. Here, we focused on dieback events affecting Mediterranean shrublands dominated by the Phoenician juniper (Juniperus phoenicea) since the middle 2000s in three sites across a wide geographical and climatic gradient in Spain. We compared their growth responses to climate and drought with coexisting tree species (Pinus pinea, Pinus pinaster and Quercus faginea), which did not show dieback in response to drought. We characterized the major climatic constraints of radial growth for trees, surviving and dead junipers by quantifying climate-growth relationships. Then, we simulated growth responses to temperature and soil moisture using the process-based VS-Lite growth model. Growth of shrubs and trees was strongly reduced during extreme droughts but the highest negative growth responsiveness to climate and drought was observed in trees followed by dead junipers from the most xeric and cold sites. Growth of dead junipers responded more negatively to droughts prior to the dieback than co-occurring, living junipers. Growth was particularly depressed in the dead junipers from the warmest site after the warm and dry 1990s. The growth model showed how a steep precipitation reduction in the 1980s triggered soil moisture limitation at the driest sites, affecting growth, particularly in the case of dead junipers and mainly in warm and dry sites. The asynchrony in the simulated seasonal timing of drought events caused contrasting effects on growth of co-occurring shrubs and tree species, compromising their future coexistence. Junipers were particularly vulnerable to hotter droughts during the early growing season. The presented projections indicate that de-shrubification events in response to hotter droughts will be common but conditioned by site conditions. Our modelling approach provides tools to evaluate vulnerability thresholds of growth under similar drought-induced dieback and mortality processes.

中文翻译：

对更热的干旱的更高敏感性是杜鹃花枯死和地中海灌木丛死亡率的基础。

干旱引起的枯死事件已被全球报道。但是，很少有研究共同检验干旱对同时发生的灌木和树木物种生长的作用，表现出不同的枯死和死亡率。在这里，我们集中讨论了影响自2000年代中期以来由腓尼基杜松（Juniperus phoenicea）主导的地中海灌丛的枯萎事件，分布在西班牙的三个地理和气候梯度较大的地区。我们将它们对气候和干旱的生长响应与并存的树种（松树，松树松和栎木）进行了比较，这些树种并未显示出对干旱的消亡。通过量化气候与生长之间的关系，我们描述了树木，幸存的杜鹃和枯死的杜松树径向生长的主要气候约束。然后，我们使用基于过程的VS-Lite生长模型模拟了对温度和土壤水分的生长响应。在极端干旱期间，灌木和树木的生长强烈减少，但是在树木中观察到对气候和干旱的最大负增长响应能力，其次是枯萎的杜松，它们来自最干旱和寒冷的地方。死去的杜松子树的生长对死亡之前的干旱的反应比同时发生的活着的杜松子树对干旱的负面影响更大。在1990年代温暖干燥的季节之后，从最温暖的地点死去的杜松树的生长特别受到抑制。生长模型显示了1980年代急剧减少的降水如何在最干燥的地点引发土壤水分限制，从而影响了生长，特别是在枯死的杜鹃花的情况下，主要是在温暖和干燥的地点。干旱事件的模拟季节定时中的异步性对共生灌木和乔木的生长产生了相反的影响，损害了它们未来的共存。瞻博网络在生长期早期特别容易遭受更热的干旱。提出的预测表明，应对较热干旱的去灌木化事件很常见，但受场地条件的影响。我们的建模方法提供了评估类似干旱导致的枯死和死亡过程下生长的脆弱性阈值的工具。提出的预测表明，应对较热干旱的去灌木化事件很常见，但受场地条件的影响。我们的建模方法提供了评估类似干旱导致的枯死和死亡过程下生长的脆弱性阈值的工具。提出的预测表明，应对较热干旱的去灌木化事件很常见，但受场地条件的影响。我们的建模方法提供了评估类似干旱导致的枯死和死亡过程下生长的脆弱性阈值的工具。

更新日期：2020-02-26

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