Bagaria G., Rodà F., Pino J. (2019) Extinction and colonisation of habitat specialists drive plant species replacement along a Mediterranean grassland-forest succession. Journal of Vegetation Science. 30: 331-340.LinkDoi: 10.1111/jvs.12722
Questions: Land-use change causes shifts in species richness, which can be delayed. However, beta-diversity patterns and especially the relative role of species replacement and nestedness in these situations with time-lagged extinctions and colonisations remain unknown. We aim to (a) quantify beta-diversity change, species replacement and nestedness for vascular plants along a grassland–forest succession with time-lagged biodiversity change for more than 50 years; (b) check its consistency between all species, grassland specialists and forest specialists, and (c) identify the role of forest encroachment relative to other drivers. Study site: Prades Mountains, Catalonia (NE Iberian Peninsula). Methods: We sampled 18 sites representing a gradient in past and current grassland area and connectivity, and in forest encroachment intensity, to obtain plant composition of all species, grassland specialists and forest specialists. We quantified overall beta-diversity and its components at each species classification group along the forest encroachment gradient and other drivers. Then, we used general linear models to study (a) the change rate of beta diversity along the forest encroachment gradient and (b) the relative importance of the drivers in explaining beta diversity. Results: Following the forest encroachment gradient, we found an overall noticeable species replacement, while nestedness was the main component for habitat specialists. Landscape differences contributed to explaining most compositional differences (both nestedness and replacement), while soil characteristics and geographic distance had a more restricted contribution. Conclusions: Species replacement due to environmental sorting occurred over the succession, triggered by selective extinctions of grassland specialists and selective colonisations of forest specialists. Nonetheless, historical landscape characteristics, current landscape characteristics and geographic distance modulate plant extinctions and colonisations, suggesting biological inertia, mass effects and habitat isolation, respectively. Partitioning beta-diversity into nestedness and replacement components and exploring the extinction and colonisation patterns of habitat specialist groups might provide relevant insight into the drivers and processes of community shift after land-use change. © 2019 International Association for Vegetation Science
Bagaria, G., Rodà, F., Clotet, M., Míguez, S., Pino, J. (2017) Contrasting habitat and landscape effects on the fitness of a long-lived grassland plant under forest encroachment: Do they provide evidence for extinction debt?. Journal of Ecology. : 0-0.LinkDoi: 10.1111/1365-2745.12860
Bagaria G., Helm A., Rodà F., Pino J. (2015) Assessing coexisting plant extinction debt and colonization credit in a grassland–forest change gradient. Oecologia. 179: 823-834.LinkDoi: 10.1007/s00442-015-3377-4
Changes in species richness along the ecological succession gradient may be strongly determined by coexisting extinction debts of species from the original habitats and colonization credits of those from the replacing habitats. The magnitude of these processes and their causes remain largely unknown. We explored the extinction debt and colonization credit for grassland and forest specialist plants, respectively, and the local and landscape factors associated to the richness of these species groups in a 50-year process of forest encroachment into semi-natural Mediterranean grasslands. A set of sampling plots of persistent grasslands and forests and their transitional habitat (wooded grasslands) was selected within fixed-area sites distributed across the landscape. Our results confirm the extinction debt and suggest colonization credit (according to observed trends and model predictions) in wooded grasslands when compared to persistent forests, despite wooded grasslands and persistent forests having similar tree cover. Grassland connectivity and solar radiation had opposing effects on the richness of both grassland and forest specialists, and it is possible that the availability of seed sources from old forests may have accelerate the payment of colonization credit in the wooded grasslands. These results suggest that extinction debt and colonization credit have driven species turnover during the 50 years of forest encroachment, but at different rates, and that local and landscape factors have opposing effects on these two phenomena. They also highlight the importance of documenting biodiversity time lags following habitat change when they are still in progress in order to timely and adequately manage habitats of high conservation value such as the grasslands studied here. © 2015, Springer-Verlag Berlin Heidelberg.
Fernández-Martínez M., Vicca S., Janssens I.A., Sardans J., Luyssaert S., Campioli M., Chapin F.S., Ciais P., Malhi Y., Obersteiner M., Papale D., Piao S.L., Reichstein M., Rodà F., Peñuelas J. (2015) Reply to 'Uncertain effects of nutrient availability on global forest carbon balance' and 'Data quality and the role of nutrients in forest carbon-use efficiency'. Nature Climate Change. 5: 960-961.LinkDoi: 10.1038/nclimate2794
[No abstract available]
Fernandez-Martinez M., Vicca S., Janssens I.A., Sardans J., Luyssaert S., Campioli M., Chapin Iii F.S., Ciais P., Malhi Y., Obersteiner M., Papale D., Piao S.L., Reichstein M., Roda F., Penuelas J. (2014) Nutrient availability as the key regulator of global forest carbon balance. Nature Climate Change. 4: 471-476.LinkDoi: 10.1038/nclimate2177
Forests strongly affect climate through the exchange of large amounts of atmospheric CO 2 (ref.). The main drivers of spatial variability in net ecosystem production (NEP) on a global scale are, however, poorly known. As increasing nutrient availability increases the production of biomass per unit of photosynthesis and reduces heterotrophic respiration in forests, we expected nutrients to determine carbon sequestration in forests. Our synthesis study of 92 forests in different climate zones revealed that nutrient availability indeed plays a crucial role in determining NEP and ecosystem carbon-use efficiency (CUEe; that is, the ratio of NEP to gross primary production (GPP)). Forests with high GPP exhibited high NEP only in nutrient-rich forests (CUEe = 33 ± 4%; mean ± s.e.m.). In nutrient-poor forests, a much larger proportion of GPP was released through ecosystem respiration, resulting in lower CUEe (6 ± 4%). Our finding that nutrient availability exerts a stronger control on NEP than on carbon input (GPP) conflicts with assumptions of nearly all global coupled carbon cycle-climate models, which assume that carbon inputs through photosynthesis drive biomass production and carbon sequestration. An improved global understanding of nutrient availability would therefore greatly improve carbon cycle modelling and should become a critical focus for future research. © 2014 Macmillan Publishers Limited.
Guardiola M., Pino J., Roda F. (2013) Patch history and spatial scale modulate local plant extinction and extinction debt in habitat patches. Diversity and Distributions. 19: 825-833.LinkDoi: 10.1111/ddi.12045
Aim: Many species exhibit a time-lag between habitat loss and its extinction, resulting in extinction debt. Although extinction debt is considered a widespread phenomenon, differences in methodological approaches can affect its detection. We aim to contribute to this methodological debate by exploring whether extinction debt is either a phenomenon common to all patches or idiosyncratic to the patch and landscape attributes of a given patch. We also aim to determine whether the scale dependency of species richness might help to explain extinction debt. Location: Southern Catalonia (NE Iberian Peninsula). Methods: We studied the effects of habitat loss on plant species richness (total, specialists and generalists) in stable (habitat loss
Bagaria G., Pino J., Rodà F., Guardiola M. (2012) Species traits weakly involved in plant responses to landscape properties in Mediterranean grasslands. Journal of Vegetation Science. 23: 432-442.LinkDoi: 10.1111/j.1654-1103.2011.01363.x
Questions: What is the role of landscape structure and dynamics, compared with climatic and geographic factors, in determining species frequencies of grassland plant specialists under habitat loss? Do species traits mediate the relationship between plant community composition and environmental variables? Location: The Mediterranean mountain grasslands of southern Catalonia (NE Iberian Peninsula), over an area of 100 × 20 km. Methods: Using redundancy analysis (RDA), we explored the association between frequency of broad plant specialists and both present and past habitat patterns in the landscape (i.e. habitat amount and reduction over the period 1956-2003), after accounting for the effect of geographical location and climate in 29 grassland patches. Then, we constructed a database of biological and ecological plant traits potentially related to population persistence, in order to assess the role of these traits in explaining the found association between species composition and environmental variables. We used a single, three-table ordination analysis (RLQ) of the species frequencies, environmental variables and species traits to relate species traits to environmental variables, after allowing for phylogenetic dependence of traits. Results: The main environmental gradient explaining species frequencies was climatic and geographic. Habitat amount in the current landscape significantly affected species frequencies, while habitat amount in the past landscape did not. A weak but significant association of species traits with environmental variables was detected. Taking into account the phylogenetic signal in plant traits did not change the results. Conclusions: Plant species in Mediterranean grasslands seem to respond quickly to landscape change, since no effect of past landscape structure was observed on current species frequencies. Moreover, plant traits did not play a major role in mediating species response to environmental variation in these grasslands. Our findings differ from those obtained in northern and central European grasslands, probably due to differences in methodology but also to the smaller contrast in environmental conditions between grasslands and the adjacent forests and scrub in Mediterranean landscapes. © 2011 International Association for Vegetation Science.
Àvila A., Rodà F. (2012) Changes in atmospheric deposition and streamwater chemistry over 25years in undisturbed catchments in a Mediterranean mountain environment. Science of the Total Environment. 434: 18-27.LinkDoi: 10.1016/j.scitotenv.2011.11.062
Surface water chemistry has changed in response to reduced atmospheric deposition of sulphur and acidity in many regions of Europe and North America. Most of these studies come from acidic or low-alkalinity surface waters under high acidic deposition. Mediterranean climates offer a different biogeochemical context, characterised by streamwaters of higher alkalinity and low acid inputs. In this paper, we use surveys of streamwater chemistry conducted in 1981-1984 and again in 2007 in the Montseny natural park (NE Spain) to test whether streamwaters of these well-buffered catchments respond to changes in atmospheric deposition, which has declined for S during the last decades in NE Spain while remaining about stable for nitrogen. The 23 sampled streams drained heathland, beech forests and evergreen oak forests in relatively undisturbed small catchments underlain by silicate bedrock. Bulk deposition of sulphate at Montseny decreased by 54% while nitrate bulk deposition increased (non-significantly) by 30% in this period. Total N deposition is estimated in the range 15-30kg Nha-1y-1 for NE Spain. This is well above threshold values (e.g. 10kg Nha-1y-1) reported as starting nitrogen saturation symptoms in forest ecosystems in Europe. Baseflow sulphate concentrations decreased on average by 47μeqL-1 or 29% of early 1980s concentrations. Baseflow mean nitrate concentrations increased significantly but only from 5.5 to 8.9μeqL-1. Thus, despite decades of high N deposition, these ecosystems appear to be still far from N saturation. Baseflow alkalinity and base cation concentrations increased substantially, probably a combined result of decreased S deposition, enhanced silicate weathering under current higher temperatures, reduced plant cation uptake as vegetation matures, and slightly drier conditions in the survey of 2007. Overall, these well-buffered catchments have shown sizable changes in baseflow chemistry in response to changed atmospheric deposition and other environmental changes. © 2011 Elsevier B.V.
Avila A, Rodà F (2011) Changes in atmospheric deposition and streamwater chemistry over 25 years in undisturbed catchments in a Mediterranean mountain environment. Science of the Total Environment doi: org/10.1016/j.scitotenv.2011.11.062.
Pino J, Guardiola M, Rodà F, Stefanescu C (2011) El deute d’extinció: una amenaça latent en una Catalunya canviant?. L'Atzavara 20: 17-27.
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