Abstract
Globally, mediterranean-climate ecosystem vegetation has converged on an evergreen, sclerophyllous and shrubby growth form. The particular aspects of mediterranean-climate regions that contribute to this convergence include summer droughts and relatively nutrient-poor soils. We hypothesised that winter-precipitation implies stressful summer droughts and leaches soils due to greater water availability (i.e. balance between precipitation and potential evapotranspiration; P–PET) during cold periods. We conducted a comparative analysis of normalised difference vegetation indices (NDVI) and edaphic and climate properties across the biomes of South Africa. NDVI was strongly correlated with both precipitation and P–PET (r2 = 0.8). There was no evidence, however, that winter-precipitation reduces NDVI in comparison to similar amounts of summer-precipitation. Base saturation (BS), a measure of soil leaching was, however, negatively related to P–PET (r2 = 0.64). This led to an interaction between P–PET and BS in determining NDVI, indicating the existence of a trade-off between water availability and soil nutrients that enables NDVI to increase with precipitation, despite negative consequences for soil nutrient availability. The mechanism of this trade-off is suggested to be that water increases nutrient accessibility. This implies that along with nutrient-depauperate geologies and long periods of time since glaciation, the winter-precipitation may have contributed to the highly leached status of the soils. Since many of the ecophysiological characteristics of mediterranean-ecosystem flora are associated with low nutrient availabilities (e.g. evergreen foliage, sclerophylly, cluster roots), we conclude that mediterranean-climates promote convergence of growth-forms in these regions through high leaching capacity.
Highlights
Despite their small spatial extent (5% global land surface [1]), mediterranean-climate ecosystems including maquis (Mediterranean Basin), chaparral (California), matorral (Chile), fynbos (South Africa) and mallee and kwongan (Australia) are home to 20% of global vascular plantPLOS ONE | DOI:10.1371/journal.pone.0144512 December 9, 2015Consequences of Precipitation Seasonality for Mediterranean-Ecosystems species, and are associated with large numbers of rare and endemic plants [2]
These diverse vegetation types are associated with a wide range of geologies, topographic variability and strong climatic gradients, which all contribute to niche heterogeneity and potentially to the maintenance of the high species richness in the Greater Cape Floristic Region (GCFR) [9], which has accumulated over long time periods [10]
Growing season normalised difference vegetation index (NDVI) maxima for the Fynbos occur in both spring (Aug) and summer (Jan) [18], possibly as a consequence of both the diverse strategies to cope with the mediterranean-climate and the fact that this biome extends into areas where precipitation is less seasonal, and even dominated by summer-precipitation in the east [19]
Summary
Despite their small spatial extent (5% global land surface [1]), mediterranean-climate ecosystems including maquis (Mediterranean Basin), chaparral (California), matorral (Chile), fynbos (South Africa) and mallee and kwongan (Australia) are home to 20% of global vascular plantPLOS ONE | DOI:10.1371/journal.pone.0144512 December 9, 2015Consequences of Precipitation Seasonality for Mediterranean-Ecosystems species, and are associated with large numbers of rare and endemic plants [2]. Part of the Greater Cape Floristic Region (GCFR) occurs in the mediterranean-climate region of southern Africa [7] and comprises fynbos, strandveld and renosterveld (all subsumed in the Fynbos biome, Fynbos), the Succulent Karoo and Afromontane forests [8] These diverse vegetation types are associated with a wide range of geologies, topographic variability and strong climatic gradients, which all contribute to niche heterogeneity and potentially to the maintenance of the high species richness in the GCFR [9], which has accumulated over long time periods [10]. Water is abundant in winter when temperatures and light availability are low, resulting in partial asynchrony between resource availability and growth [12] These circumstances are thought to have resulted in a number of evolutionary specializations of the GCFR flora. Growing season normalised difference vegetation index (NDVI) maxima for the Fynbos occur in both spring (Aug) and summer (Jan) [18], possibly as a consequence of both the diverse strategies to cope with the mediterranean-climate and the fact that this biome extends into areas where precipitation is less seasonal, and even dominated by summer-precipitation in the east [19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
