Riparian vegetation research in Mediterranean-climate regions: common patterns, ecological processes, and considerations for management

Abstract

Riparian corridors in Mediterranean-climate regions (med-regions) are resource-rich habitats within water-limited, larger landscapes. However, little is known about how their plant communities compare functionally and compositionally across medregions. In recent decades, research on these ecosystems has expanded in both geographic scope and disciplinary depth. We reviewed 286 riparian-vegetation studies across the five med-regions, and identified common themes, including: (1) high levels of plant biodiversity, structural complexity, and cross-region species introductions; (2) strong physical controls on plant demographics and community structure; and (3) intensive human impacts. European and Californian ecosystems were the most represented among the studies reviewed, but Australia, South Africa, and Chile had the greatest proportional increases in articles published since 2000. All med-regions support distinct riparian flora, although many genera have invaded across regions. Plant species in all regions are adapted to multiple abiotic stressors, including dynamic flooding and sediment regimes, seasonal water shortage, and fire. The most severe human impacts are from land-use conversion to agriculture, streamflow regulation, nutrient enrichment, and climate change. Current knowledge gaps and subjects for future research include cumulative impacts to small, ephemeral streams and large, regulated rivers, as well as understudied ecosystems in North Africa, the western Mediterranean basin, and Chile.Electronic supplementary material The online version of this article (

High Variability Is a Defining Component of Mediterranean-Climate Rivers and Their Biota

“…Community changes between the wet and the dry season in Mediterranean-climate regions have been reported for many aquatic organisms, including microbes (e.g., [58]), phytoplankton (e.g., [59,60]), benthic algae (e.g., [61][62][63], macroinvertebrates (e.g., [19,64,65]), and fish (e.g., [44,47,63]), and for riparian vegetation (e.g., [66]). Nevertheless, macroinvertebrates are by far the most investigated group and studies on seasonal changes have focused on whole communities as well as the composition of particular taxonomic groups (e.g., Plecoptera [67]; Trichoptera [68]; or Chironomidae [69]).…”

Linking environmental flows to sediment dynamics

“…This vegetation encroachment stabilizes the new channel, even within extraordinary floods. Prevention of vegetation encroachment could be a basic objective of effective e-Flows, particularly in Mediterranean streams, where common irrigation reservoirs release high summer flows, thus supporting maximum plant growth potential as the normal summer drought is eliminated (Magdaleno & Fernández, 2011;Stella et al, 2013;González del Tánago et al, 2015;Lobera et al, 2015). Ultimately, regulated river dimensions are so reduced that they develop into a small remnant: a 'Bonsai river'.…”

Climate Change Impacts and Water Management Adaptation in Two Mediterranean-Climate Watersheds: Learning from the Durance and Sacramento Rivers

“…Climate change may also favor alien species with a tolerance for changed conditions, specifically higher temperatures [1]. In an extensive review of riparian vegetation research across all five Mediterranean-climate regions (parts of California, Chile, South Africa, Australia, and of course the Mediterranean Basin itself), Stella et al found that one of the major human impacts these regions share is climate change [4]. While climate change is hardly…”