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11 páginas, 3 tablas, 5 figuras ; Root functional diversity of submerged vegetation exerts a major effect on nitrogen (N) cycling in lake sediments. This fact, however, is neglected in current N-balance models because the links between the engineering role of plants and in situ microbial N cycling are poorly understood. We hypothesized that macrophyte species with high root oxygen loss (ROL) capacity promote the highest denitrification because of a higher abundance of ammonia oxidizers and tighter coupling between nitrifiers and denitrifier communities. We sampled five small ultraoligotrophic shallow lakes with abundant macrophyte cover including sediments dominated either by Isoetes spp. (high ROL), mixed communities of natopotamids (low ROL), and unvegetated sandy sediments. At each site, we quantified denitrification (DNT) rates and proxies for the abundance of denitrifiers (nirS and nirK genes), and both ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) and the diversity of nirS-harboring bacteria. Vegetated sediments showed significantly higher abundances of N-cycling genes than bare sediments. Plant communities dominated by Isoetes generated sediments with higher redox and NO2 3 concentrations and significantly higher DNT rates than natopotamidsdominated landscapes. Accordingly, increasing DNT rates were observed along the gradient from low ROL plants-bare sediments-high ROL plants. Significantly higher abundance of the archaeal amoA gene was recorded in sediments colonized by high ROL plants unveiling a key biogeochemical role for AOA in coupling macrophyte landscape and ecosystem denitrification. ; MVC was supported by a Juan de la Cierva fellowship from the Spanish Office for Research (MINECO) and a Beatriu de Pin os from the Catalan Government. This research was granted by projects DARKNESS CGL2012-32747 (MINECO) to EOC and AQUAREST (OAPN 212/2010) to EG. EC, EOC and EG are members of the Environmental Changes Ecology Group (GECA), an Excellence Research Group (SGRDGR), of the Generalitat de Catalunya (Ref. 2014 SGR 1249. 2014–2017). ; Peer reviewed

Este artículo contiene 18 páginas, 5 figuras, 3 tablas ; Species distribution models (SDMs) have been used to predict potential distributions of habitats and to model the effects of environmental changes. Despite their usefulness, currently there is no standardized sampling strategy that provides suitable and sufficiently representative predictive models for littoral marine benthic habitats. Here we aim to establish the best performing and most cost-effective sample design to predict the distribution of littoral habitats in unexplored areas. We also study how environmental variability, sample size, and habitat prevalence may influence the accuracy and performance of spatial predictions. For first time, a large database of littoral habitats (16,098 points over 562,895 km of coastline) is used to build up, evaluate, and validate logistic predictive models according to a variety of sampling strategies. A regularly interspaced strategy with a sample of 20% of the coastline provided the best compromise between usefulness (in terms of sampling cost and effort) and accuracy. However, model performance was strongly depen upon habitat characteristics. The proposed sampling strategy may help to predict the presence or absence of target species or habitats thus improving extensive cartographies, detect high biodiversity areas, and, lastly, develop (the best) environmental management plans, especially in littoral environments. ; This study was supported by INTRAMURAL CSIC (0065) and the European Union's Horizon 2020 (689518) MERCES. ; Peer reviewed

Este artículo contiene 14 páginas, 3 tablas, 3 figuras. ; Aim: We studied global variation in beta diversity patterns of lake macrophytes using regional data from across the world. Specifically, we examined (1) how beta diversity of aquatic macrophytes is partitioned between species turnover and nestedness within each study region, and (2) which environmental characteristics structure variation in these beta diversity components. Location: Global. Methods: We used presence–absence data for aquatic macrophytes from 21 regions distributed around the world. We calculated pairwise-site and multiple-site beta diversity among lakes within each region using Sørensen dissimilarity index and partitioned it into turnover and nestedness coefficients. Beta regression was used to correlate the diversity coefficients with regional environmental characteristics. Results Aquatic macrophytes showed different levels of beta diversity within each of the 21 study regions, with species turnover typically accounting for the majority of beta diversity, especially in high-diversity regions. However, nestedness contributed 30–50% of total variation in macrophyte beta diversity in low-diversity regions. The most important environmental factor explaining the three beta diversity coefficients (total, species turnover and nestedness) was elevation range, followed by relative areal extent of freshwater, latitude and water alkalinity range. Main conclusions: Our findings show that global patterns in beta diversity of lake macrophytes are caused by species turnover rather than by nestedness. These patterns in beta diversity were driven by natural environmental heterogeneity, notably variability in elevation range (also related to temperature variation) among regions. In addition, a greater range in alkalinity within a region, likely amplified by human activities, was also correlated with increased macrophyte beta diversity. These findings suggest that efforts to conserve aquatic macrophyte diversity should primarily focus on regions with large numbers of lakes that exhibit broad environmental gradients. ; The gathering of the Finnish data was partly supported by Biological Monitoring of Finnish Freshwaters under diffuse loading -project (XPR3304) financed by Ministry of Agriculture and Forestry and partly by national surveillance monitoring programs of lakes. S.H. and M.M. were supported by the EU-funded MARS-project (7th EU Framework Programme, Contract No.: 603378).Swedish macrophyte data were collected within the Swedish Monitoring Program of macrophytes in lakes funded by the Swedish Agency for Marine and Water Management. S.K. was supported by NWO Veni grant 86312012. Macrophyte data from Brazilian Amazon were collected within a limnological monitoring program funded by Vale S.A. The vast majority of macrophyte data from Polish lakes were collected within the State Environmental Monitoring Programme and were provided by the Inspection for Environmental Protection. Macrophyte data for British lakes were collated by the Joint Nature Conservation Committee from surveys resourced by the national conservation agencies. Swiss macrophytes data were collected during a study financially supported by the Swiss Federal Office for the Environment. Wisconsin data collection was funded by the Wisconsin Department of Natural Resources and supported by the Wisconsin Cooperative Fishery Research Unit. The Norwegian macrophyte data were collected within the European Union project 'LAKES – Long distance dispersal of Aquatic Key Species', contract no. env4-ct-97-0585. ; Peer reviewed