Drylands occupy 47% of the world’s terrestrial area and comprise important biodiversity hotspots such as the Mediterranean Basin, where one can find high levels of plant diversity and endemism. At the same time, they provide resources for human populations, being cattle grazing one of the main activities in dryland ecosystems. Mediterranean woodlands and pastures are currently under threat with increasing aridity due to climate change. Aridity, together with human exploitation, pushes these ecosystems towards land degradation, leading to decreased diversity, ecosystem functioning, and economical value. Understanding how plant communities respond to climate in the long-term, as well as climatic fluctuations, is crucial to anticipate the impacts of climate change in these ecosystems and build a knowledge base to design adaptation and restoration measures and promote their resilience. In the western Mediterranean Basin dryland areas are commonly occupied with oak open woodlands. It is an agro-silvo-pastoral system with a savannah-like structure, dominated by oaks with a species-rich understory of pastures and shrubs. In Portugal, this system is called montado, and due to its socio-economic and ecological importance, it is currently monitored within the LTsER montado platform. The herbaceous layer, dominated by annual species, is a major component of this system’s diversity. While these pastures are adapted to dryland climatic conditions, its annual turnover may make these communities quick responders to environmental changes, providing a good model system to study the effects of climate on diversity and ecosystem functioning. In this work, we aim to assess the effects of long-term climate and yearly climatic fluctuations on plant taxonomic and functional diversity and on pasture productivity, as well as the relationship between diversity and productivity. We sampled the understory plant community of 10 holm-oak open woodlands along a spatial aridity gradient in southern Portugal in multiple years, 5-7 times, between 2012 and 2022. A stratified random selection of sites was made, avoiding as much as possible confounding effects, namely from differences in slope, elevation and fire occurrence. The plant community was sampled in spring, at the peak standing biomass, with the point-intercept method along six 20 m transects per site. Pasture productivity was measured by collecting the aerial herbaceous biomass in three 30 cm squares placed randomly in each site. Functional diversity was calculated using mean trait values per species retrieved from online databases. We fit linear mixed-effects models to assess the relationship between long- and short-term climate variables and taxonomic and functional diversity. We further explored the role of diversity on productivity with structure equation modeling. To assess the patterns of compositional changes along space and time, we determined compositional and functional dissimilarity among sites and among years. Preliminary results show that both productivity and species diversity increase with annual precipitation and winter temperature, while long-term aridity does not seem to be a main driver. On the other hand, species compositional changes between years suggests that more arid sites have higher species turnover, and possibly a higher species richness considering both dry and more wet years, while less arid sites are more stable along time. In this presentation, we will further explore these patterns and assess the role of functional traits and functional diversity as a means by which communities adapt to climatic conditions, and how these influence pasture productivity. These findings may then contribute to a discussion on the projections on future scenarios for these ecosystems and which adaptation and restoration measures may be adopted to promote its sustainability and resilience.
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Jun 1, 2025
Ana Cláudia Delciellos + 4
Just Published
Open Access