CREAF

The chemical composition of the atmosphere has significantly changed in the last century, mostly due to increased emissions of gases and particles derived from human activities. Several studies have analyzed the trends in the chemical composition of rainwater and atmospheric deposition in recent decades in central and northern Europe. However, for Spain there is a lack of studies at national level. Up to now, analyses of decadal trends are only available from a few individual stations. In this paper we first present the different methods to measure atmospheric deposition. Then we compile a list of atmospheric deposition monitoring stations in Spain and review the available time series, for series longer than 10 years, with special attention to the trends of N, S and African dust. Finally, we indicate future research directions to fill the gaps in knowledge about patterns and trends of atmospheric deposition at a national level. © 2017 Los Autores. Editado por la AEET.

Water stored underground in the saturated and subsurface zones below the soil are important sources of water for plants in water-limited ecosystems. The presence of deep-rooted plants worldwide, however, suggests that the use of groundwater is not restricted to arid and seasonally dry ecosystems. We compiled the available data (71 species) on the relative contribution of groundwater to plant water estimated using stable isotopes and mixing models, which provided information about relative groundwater use, and analyzed their variation across different climates, seasons, plant types, edaphic conditions, and landscape positions. Plant use of groundwater was more likely at sites with a pronounced dry season, and represented on average 49 per cent of transpired water in dry seasons and 28 per cent in wet seasons. The relative contribution of groundwater to plant-water uptake was higher on rocky substrates (saprolite, fractured bedrock), which had reduced groundwater uptake when this source was deep belowground. In addition, we found that the connectivity between groundwater pools and plant water may be quantitatively larger and more widespread than reported by recent global estimations based on isotopic averaged values. Earth System Models should account for the feedbacks between transpiration and groundwater recharge. © 2017 The Author(s).