Taxonomical and functional diversity turnover in Mediterranean grasslands: interactions between grazing, habitat type and rainfall

Abstract

Summary1. Changes in livestock grazing regimes are among the most important drivers of species loss and decrease in functional diversity world-wide. However, taxonomic and functional diversities (TD and FD) can respond differently to changes in grazing regime or productivity. 2. We surveyed plant communities from 67 sites under different grazing regimes (from heavy grazing to grazing abandonment) in wet and dry habitats, in both wet and dry years. We tested the influence of grazing intensity, habitat type and rainfall on TD, FD and the relationship between them. We also partitioned diversity to examine the effects of grazing on TD and FD across scales (within communities, within grazing levels and between grazing levels). 3. The effect of grazing within and across communities was modulated by water availability, with grazing showing the strongest effects in dry habitats. The relationship between FD and TD varied between habitat types and years and revealed high functional similarity between species (i.e. redundancy) in dry habitats. TD was reduced in the driest conditions across all the observation levels, contrasting with the high temporal stability of FD, suggesting that FD was decoupled from TD, especially in dry habitats. However, despite the high temporal and spatial stability of FD, results show that under severely limited water availability, high grazing pressure can reduce FD, revealing a convergence in traits under the combined effect of grazing and drought conditions. 4. Synthesis and applications. Results highlight the dependence of functional diversity on the combined effect of water availability and grazing regime. Under severely limited water availability, grazing intensification reduced the functional diversity of these grasslands. Because of the foreseeable reduction in water availability in Mediterranean environments, we recommend the adoption of flexible grazing management schemes that take species and functional diversities into account simultaneously and adapt the level of grazing pressure to water availability.

Impacts of Global Change on Mediterranean Forests and Their Services

“…Scenarios of increasing drought suggest that Mediterranean grasslands could lose species diversity by affecting particular species [175]. Grazing management should be reconsidered to provide appropriate levels of grazing pressure, because the impacts of grazing on grassland biomass and diversity can be very detrimental and can endanger the capacity of grassland services, and should be reconsidered to allow further grazing, especially in a scenario of increased aridity [176,177]. Important grassland types, such as semi-natural calcareous grasslands, have evolved with the history of human activity, which has generated and maintained these habitats by extensive grazing and mowing.…”

“…N deposition in the Mediterranean Basin has produced a continuous increase in nitrophylic plant species, such as those detected in the Iberian Peninsula between 1900 and 2008 [244]. The decrease in the diversity and cover of plant communities due to drought can even be larger when drought coincides with extensive agricultural grazing [176].…”

How can forage production in Nordic and Mediterranean Europe adapt to the challenges and opportunities arising from climate change?

“…With increased precipitation levels, care is needed to minimize soil compaction during farm operations, and maintain or improve drainage systems, particularly on some soil types (Rivedal et al, 2016). In the driest Mediterranean semi-natural grasslands dominated by annual species, grazing by livestock is recognized as the main driver influencing vegetation dynamics, species diversity and grassland productivity (Köchy et al, 2008;Carmona et al, 2012;Sternberg et al, 2015), and thus needs to be managed carefully, e.g. through the use of flexible stocking (Pahl et al, 2016).…”

Overgrazing in the Montado? The need for monitoring grazing pressure at paddock scale

“…Besides herbage mass availability, plant diversity and nutritive quality also vary seasonally, among years and with spatial location as occurs along a topographic slope (Carmona et al 2012;Pérez Corona et al 1998;Vázquez-de-Aldana et al 2008). Protein decreases sharply during the growing season (Fig.…”