Botany Department, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
New Phytol. 2012 Jul;195(2):396-407. doi: 10.1111/j.1469-8137.2012.04170.x. Epub 2012 May 17.
• Mediterranean-type ecosystems contain 20% of all vascular plant diversity on Earth and have been identified as being particularly threatened by future increases in drought. Of particular concern is the Cape Floral Region of South Africa, a global biodiversity hotspot, yet there are limited experimental data to validate predicted impacts on the flora. In a field rainout experiment, we tested whether rooting depth and degree of isohydry or anisohydry could aid in the functional classification of drought responses across diverse growth forms. • We imposed a 6-month summer drought, for 2 yr, in a mountain fynbos shrubland. We monitored a suite of parameters, from physiological traits to morphological outcomes, in seven species comprising the three dominant growth forms (deep-rooted proteoid shrubs, shallow-rooted ericoid shrubs and graminoid restioids). • There was considerable variation in drought response both between and within the growth forms. The shallow-rooted, anisohydric ericoid shrubs all suffered considerable reductions in growth and flowering and increased mortality. By contrast, the shallow-rooted, isohydric restioids and deep-rooted, isohydric proteoid shrubs were largely unaffected by the drought. • Rooting depth and degree of iso/anisohydry allow a first-order functional classification of drought response pathways in this flora. Consideration of additional traits would further refine this approach.
• 地中海型生态系统包含地球上所有维管植物多样性的 20%，已被确定为特别受到未来干旱加剧的威胁。特别令人关注的是南非的开普植物区，这是一个全球生物多样性热点地区，但对于预测对植物区系的影响，其实验数据非常有限。在一项田间雨淋实验中，我们测试了根深度和等水或不等水程度是否有助于对不同生长形式的干旱响应进行功能分类。• 我们在山地 fynbos 灌丛中进行了为期 6 个月的夏季干旱实验，持续了 2 年。我们监测了 7 个物种的一系列参数，从生理特征到形态结果，这些物种包括三种主要生长形式（深根拟态灌木、浅根石南灌木和禾本科 restioids）。• 生长形式之间和内部的干旱响应都存在很大的差异。浅根、不等水的石南灌木的生长和开花都受到了相当大的减少，死亡率也增加了。相比之下，浅根、等水的 restioids 和深根、等水的拟态灌木在很大程度上不受干旱的影响。• 根深度和等水/不等水程度允许对该植物区系的干旱响应途径进行一级功能分类。考虑到其他特征将进一步完善这种方法。
