LINCGlobal, Departamento de Biogeografía y Cambio Global, Museo Nacional de Ciencias Naturales, MNCN-CSIC, Serrano 115 dpdo, 28006 Madrid, Spain.
Tree Physiol. 2013 Dec;33(12):1284-95. doi: 10.1093/treephys/tpt103. Epub 2013 Dec 5.
Plants have evolved different strategies to cope with drought, involving alternative ecophysiologies and different levels of plasticity. These strategies are critical for species of limited distribution, which are especially vulnerable to the current rates of rapid environmental change. The aim of this study was to assess the water strategy of two species with limited distribution, Cneorum tricoccon L. and Rhamnus ludovici-salvatoris Chodat., and evaluate their interpopulation variability along an aridity gradient to estimate their vulnerability to a drier climate. We measured different ecophysiological traits influenced by drought--stomatal conductance, maximum photochemical efficiency of photosynthesis II, carbon isotope ratio and chlorophyll concentration--in two climatically contrasting years, before and during summer drought. Both species were vulnerable to drought at the aridity limit of the gradient, but showed contrasting water strategies: while C. tricoccon was consistent in its water conservation strategy across the aridity gradient, R. ludovici-salvatoris was not, displaying higher and more variable stomatal conductances and being able to increase water-use efficiency at the most xeric sites. Changes in length and intensity of drought events may favor one species' strategy to the detriment of the other: C. tricoccon is more vulnerable to chronic and prolonged droughts, whereas short but acute droughts might have a stronger effect on R. ludovici-salvatoris. In those communities where these two species coexist, such different strategies might lead to changes in community structure under climate change scenarios, with unknown cascade effects on ecosystem functioning.
植物已经进化出不同的策略来应对干旱，涉及替代生态生理学和不同程度的可塑性。这些策略对于分布范围有限的物种至关重要，它们特别容易受到当前快速环境变化的影响。本研究的目的是评估两种分布范围有限的物种的水分策略，即 Cneorum tricoccon L. 和 Rhamnus ludovici-salvatoris Chodat.，并评估它们在干旱梯度上的种群间变异性，以估计它们对更干燥气候的脆弱性。我们在两个气候差异较大的年份（干旱前和干旱期间）测量了不同受干旱影响的生态生理特征——气孔导度、光合作用 II 的最大光化学效率、碳同位素比和叶绿素浓度——这两个物种在干旱梯度的干旱极限处都容易受到干旱的影响，但表现出不同的水分策略：虽然 C. tricoccon 在整个干旱梯度上保持了一致的节水策略，但 R. ludovici-salvatoris 则不然，其气孔导度更高且更具变异性，并能够在最干旱的地点提高水分利用效率。干旱事件的长度和强度的变化可能会有利于一种物种的策略，而不利于另一种物种：C. tricoccon 更容易受到慢性和长期干旱的影响，而短期但急性的干旱可能对 R. ludovici-salvatoris 产生更强的影响。在这两种物种共存的群落中，这种不同的策略可能会导致在气候变化情景下群落结构发生变化，对生态系统功能产生未知的级联效应。
