Land use and local species richness are a more important determinant of Mediterranean ecosystems´ multifunctionality than landscape diversity and habitat size

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Paula Lopezosa, Ecology, University of Alicante, Alicante, Spain and Santiago Soliveres, Ecology, Universidad de Alicante, Alicante, Spain

Background/Question/Methods
Anthropogenic disturbances include local and landscape diversity loss, habitat fragmentation and land-use changes. Whereas all these changes commonly co-occur and impair ecosystem multifunctionality, they are often studied in isolation. Therefore, we ignore the relative importance of these drivers of ecosystem change or whether or not they interact to determine ecosystem functioning. Here we present preliminary results on the response of the functioning of Mediterranean ecosystems to changes in local (plant species richness) and landscape (diversity of habitat-types) diversity, land use (from cropland to mature forests, including shrublands and afforestations) and habitat size (proportion of equal land use within a 500 m radius). We studied the response to 12 functions, including seed, insect and mammal predation rates, litter decomposition, water infiltration, nutrient cycling, tree regeneration of nutrient stocks (aboveground biomass and soil organic matter), and their collective response using a multifunctionality metric. We aimed to answer three main questions: i) which are the most important local and landscape-level drivers of ecosystem functioning?, ii) does the relative importance of these different drivers depend on the function studied?, iii) do these local and landscape drivers interact to determine the functioning of Mediterranean ecosystems?
Results/Conclusions
Local land use was by far the most important driver of ecosystem multifunctionality across the 25 study plots. It affected 50% of the measured functions and was the only significant predictor of the multifunctionality index. Excepting water infiltration and insect predation, all functions and ecosystem multifunctionality were highest in native mature forest (oak or mixed deciduous forests; MF = 0.52-0.59), average in pine regeneration or afforestation and shrubland sites (MF = 0.47-0.30), and minimal in croplands (MF = 0.26). The next predictor in importance was local species richness, which affected positively nutrient cycling, seed predation and herbivory rates, and enhanced soil organic matter and field capacity. Importantly, species richness interacted with land use, having stronger and more positive effects in those land uses with lower multifunctionality levels (e.g., croplands or shrublands) than on the rest. Habitat diversity and size were far less important than local-level drivers of functioning, affecting solely one out of 12 measured functions. Overall, our results suggest that: i) ecosystem services provided by mature native forests are hard to match by any other land use, including decades-old reforestations, and ii) management strategies aimed at increasing or maintaining high local biodiversity levels may be particularly important in degraded environments.