A quantitative assessment of mid-term risks of global change on forests in Western Mediterranean Europe

Gil-Tena A., Morán-Ordóñez A., Comas L., Retana J., Vayreda J., Brotons L. (2019) A quantitative assessment of mid-term risks of global change on forests in Western Mediterranean Europe. Regional Environmental Change. 19: 819-831.
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Doi: 10.1007/s10113-018-1437-0

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Assessment of potential forests’ threats due to multiple global change components is urgently needed since increasing exposure to them could undermine their future persistence. We aim to assess the risks to the persistence of monospecific forests in Western Mediterranean Europe posed by climate change, fire, and land-use changes (i.e., deforestation) in the short and medium terms (horizon 2040). We specifically evaluate whether the degree of risk related to the likelihood of hazard occurrence varies depending on seral stage, tree species, and climate gradients. We performed the risk assessment on forests of Catalonia (NE Spain) through a combination of correlative and process-based modeling approaches and future global change scenarios. Overall, climate suitability of forests showed a general decrease by 2040, with the exception of xeric Pinus halepensis forests mainly distributed in the driest climate of the study area. Forest stands dominated by low drought-tolerant species were at higher risk of losing climatic suitability than forests dominated by Mediterranean species. The highest fire and deforestation risks were predicted for forest stands in dry climate where human pressures are higher. Nevertheless, high deforestation risk was also attained outside the driest areas. Deforestation risk was lower in old-growth than in younger stands, whereas old-growth forests in the Wet climate or dominated by Pinus sylvestris were projected to be at higher fire risk than younger forests. Our results suggest that conservation actions should target forest stands in dry climate. Moreover, old-growth forest stands should also be prioritized due to their particular sensitivity to disturbances and their high ecological value. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

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Calibrating the severity of forest defoliation by pine processionary moth with landsat and UAV imagery

Otsu K., Pla M., Vayreda J., Brotons L. (2018) Calibrating the severity of forest defoliation by pine processionary moth with landsat and UAV imagery. Sensors (Switzerland). 18: 0-0.
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Doi: 10.3390/s18103278

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The pine processionary moth (Thaumetopoea pityocampa Dennis and Schiff.), one of the major defoliating insects in Mediterranean forests, has become an increasing threat to the forest health of the region over the past two decades. After a recent outbreak of T. pityocampa in Catalonia, Spain, we attempted to estimate the damage severity by capturing the maximum defoliation period over winter between pre-outbreak and post-outbreak images. The difference in vegetation index (dVI) derived from Landsat 8 was used as the change detection indicator and was further calibrated with Unmanned Aerial Vehicle (UAV) imagery. Regression models between predicted dVIs and observed defoliation degrees by UAV were compared among five selected dVIs for the coefficient of determination. Our results found the highest R-squared value (0.815) using Moisture Stress Index (MSI), with an overall accuracy of 72%, as a promising approach for estimating the severity of defoliation in affected areas where ground-truth data is limited. We concluded with the high potential of using UAVs as an alternative method to obtain ground-truth data for cost-effectively monitoring forest health. In future studies, combining UAV images with satellite data may be considered to validate model predictions of the forest condition for developing ecosystem service tools. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

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Assessing the distribution of forest ecosystem services in a highly populated Mediterranean region

Roces-Díaz J.V., Vayreda J., Banqué-Casanovas M., Cusó M., Anton M., Bonet J.A., Brotons L., De Cáceres M., Herrando S., Martínez de Aragón J., de-Miguel S., Martínez-Vilalta J. (2018) Assessing the distribution of forest ecosystem services in a highly populated Mediterranean region. Ecological Indicators. 93: 986-997.
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Doi: 10.1016/j.ecolind.2018.05.076

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Forest ecosystems provide a wide range of goods and services to society and host high levels of biodiversity. Nevertheless, forest ecosystem services (ES) are often quantified and assessed using simplified methodologies (e.g., proxy methods based exclusively on Land Use Land Cover maps) that introduce substantial uncertainty in the analysis by ignoring, for instance, the species composition and spatial configuration of the ecosystems studied. In this work we defined and calculated a set of 12 indicators of several ES for the forests of the highly populated region of Catalonia (North-eastern Iberian Peninsula). The indicators combined different sources of information such as forest surveys, ecological model predictions and official statistics, but also included additional land cover information. All ES indicators were aggregated at the municipality level to compare their values and distribution patterns. We assessed spatial trade-offs and synergies among ES, as well as their relationships with a set of socioeconomic, climatic and biodiversity variables using correlation analyses and mixed-effects models. The results suggest a clustering of provisioning and regulating ES in mountainous zones towards the North of the study area. These two types of services showed a high degree of spatial similarity and presented high positive correlations. In contrast, cultural ES showed a more scattered pattern, which included lower elevation areas in the South of the study region. Climatic conditions were the main determinants of the spatial variability in the supply of the different ES, with most indicators being positively associated with precipitation and negatively associated with temperature. In addition, biodiversity (particularly woody species richness) showed positive relations with most of these ES, while socioeconomic variables (such as population density and the percentage employment in agriculture) showed negative associations with most of them. The combination of information from different data sources (including primary data) allowed for a detailed analysis of forest ES, likely removing some of the problems derived from approaches based only on proxy methods. In addition, the use of municipalities as study unit makes results directly relevant to management and planning strategies operating at this scale (e.g., forest management and planning). © 2018 Elsevier Ltd

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The spatial level of analysis affects the patterns of forest ecosystem services supply and their relationships

Roces-Díaz, J.V., Vayreda, J., Banqué-Casanovas, M., Díaz-Varela, E., Bonet, J.A., Brotons, L., de-Miguel, S., Herrando, S., Martínez-Vilalta, J. (2018) The spatial level of analysis affects the patterns of forest ecosystem services supply and their relationships. Science of the Total Environment. 626: 1270-1283.
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Doi: 10.1016/j.scitotenv.2018.01.150

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Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain

Doblas-Miranda E., Rovira P., Brotons L., Martinez-Vilalta J., Retana J., Pla M., Vayreda J. (2013) Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain. Biogeosciences. 10: 8353-8361.
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Doi: 10.5194/bg-10-8353-2013

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Accurate estimates of C stocks and fluxes of soil organic carbon (SOC) are needed to assess the impact of climate and land use change on soil C uptake and soil C emissions to the atmosphere. Here, we present an assessment of SOC stocks in forests, shrublands and grasslands of peninsular Spain based on field measurements in more than 900 soil profiles. SOC to a depth of 1 m was modelled as a function of vegetation cover, mean annual temperature, total annual precipitation, elevation and the interaction between temperature and elevation, while latitude and longitude were used to model the correlation structure of the errors. The resulting statistical model was used to estimate SOC in the ∼8 million pixels of the Spanish Forest Map (29.3 × 106 ha). We present what we believe is the most reliable estimation of current SOC in forests, shrublands and grasslands of peninsular Spain thus far, based on the use of spatial modelling, the high number of profiles and the validity and refinement of the data layers employed. Mean concentration of SOC was 8.7 kg m-2, ranging from 2.3 kg m-2 in dry Mediterranean areas to 20.4 kg m -2 in wetter northern locations. This value corresponds to a total stock of 2.544 Tg SOC, which is four times the amount of C estimated to be stored in the biomass of Spanish forests. Climate and vegetation cover were the main variables influencing SOC, with important ecological implications for peninsular Spanish ecosystems in the face of global change. The fact that SOC was positively related to annual precipitation and negatively related to mean annual temperature suggests that future climate change predictions of increased temperature and reduced precipitation may strongly reduce the potential of Spanish soils as C sinks. However, this may be mediated by changes in vegetation cover (e.g. by favouring the development of forests associated to higher SOC values) and exacerbated by perturbations such as fire. The estimations presented here provide a baseline to estimate future changes in soil C stocks and to assess their vulnerability to key global change drivers, and should inform future actions aimed at the conservation and management of C stocks. © 2013 Author(s).

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Reassessing global change research priorities in mediterranean terrestrial ecosystems: How far have we come and where do we go from here?

Doblas-Miranda E., Martinez-Vilalta J., Lloret F., Alvarez A., Avila A., Bonet F.J., Brotons L., Castro J., Curiel Yuste J., Diaz M., Ferrandis P., Garcia-Hurtado E., Iriondo J.M., Keenan T.F., Latron J., Llusia J., Loepfe L., Mayol M., More G., Moya D., Penuelas J., Pons X., Poyatos R., Sardans J., Sus O., Vallejo V.R., Vayreda J., Retana J. (0) Reassessing global change research priorities in mediterranean terrestrial ecosystems: How far have we come and where do we go from here?. Global Ecology and Biogeography. 24: 25-43.
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Doi: 10.1111/geb.12224

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Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. Location: Mediterranean terrestrial ecosystems. Methods: This article revisits the research priorities proposed in a 1998 assessment. Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. Main conclusions: (1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.

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