1,721,083 research outputs found
Analisi delle distribuzioni taglia-abbondanza in comunità a base detrito nel bacino del fiume Tirso (Sardegna).
No full textInter- and intra-habitat variability of plant detritus decomposition in a transitional environment (Lake Alimini, Adriatic Sea)
No full textA comparative analysis of inter- and intra-habitat variations of detritus decay rates across ecosystem types was carried out in the Lake Alimini complex (Italy) to assess the relevance of major structural ecosystem features on detritus processing rates. Reed (Phragmites australis) detritus decomposition was studied in a stream, a freshwater lake and a salt marsh on a seasonal basis at a total of 20 sampling stations using the leaf pack technique. Overall, the spatial variability of leaf decomposition rates was more pronounced than the temporal variability, decomposition rates in the stream being 3.6 and 5.2 times faster than in the freshwater lake and salt marsh, respectively. The intra-habitat spatial variability of leaf decay rates in the stream was also higher than in the other systems. Environmental features were relevant factors affecting intra- and inter-habitat variation of reed decay rates, and their relevance to leaf detritus decomposition showed a strong seasonal variation
Wrap-up special session: Relationships between sediment and biota in transitional water ecosystems and harbours
No full textExploring effects of sediment resuspension on biota ...How to do more with less ?... A possible strategy to reduce costs of monitoring program could be
represented by the development of the biomarker approach in new and more suitable species (i.e. macrobenthos?) and
the selection of new biomarkers to evaluate early stress on aquatic communities
Summer drought disturbance on plant detritus decomposition processes in three River Tirso (Sardinia, Italy) sub-basins
No full textHere, we study the variation patterns of detritus decomposition along a river continuum in a Mediterranean type river basin, and the influence of summer drought disturbance on this pattern. The study was carried out in three 4th order sub-basins (hereafter referred to as Assolo, Laconi and Olzai) of the river Tirso basin (Sardinia, ITALY), with one study site per stream order in each sub-basin (4 stream orders × 3 sub-basins = 12 study sites). The
three sub-basins were selected according to their exposure to summer drought, Assolo being the most exposed and Laconi the least exposed. Reed (Phragmites australis (Cav.) Steudel) detritus decomposition was studied during the fall and spring periods, utilising the leaf packs technique with 3 sampling dates and 8 replicate packs per sample in each period. At all sites, the stream width was recorded fortnightly for one year. Overall, the reed leaf packs underwent rapid decomposition in the river Tirso basin (k = 0.0193 d−1), but very high variation was observed among leaf pack decomposition rates (C.V. = 112.7%). Seasons, sub-basins, and stream orders accounted for 88% of the total variance observed (Three Way ANOVA). The decomposition rate was significantly higher in spring than in fall, in the Laconi sub-basin than in the Olzai and Assolo sub-basins, and in 4th order streams than in 2nd and 3rd. Decomposition rates were also higher at relatively undisturbed sites than at the study sites exposed to complete summer desiccation (e.g., 2nd, 3rd, 4th in the Olzai sub-basin; 1st, 2nd, 3rd in the Assolo sub-basin). The strongest effects of summer drought disturbance occurred at the lowest order stream branches (i.e., 1st and 2nd order) suggesting that the resilience of detritus decomposition processes to the disturbance arising from Mediterranean type climates increases with stream order
Heterogeneity of body size structure of detritus based guilds in the River Tirso basin (Sardinia, Italy).
No full textIfrane, Marocc
La sfida della Direttiva Quadro Acqua dell’UE per la conservazione delle risorse idriche in Europa The challenge of EU Water Framework Directive for water resources preservation in Europe
No full textSustainable water resource management is a strategic objective of UE and represents a major challenge for developing countries, which socio-economic development in the next few years cannot be paid by environmental resource depletion and drastic decrease of ecosystem health. Monitoring aquatic ecosystems health is a basic requirement for the achievement of strong sustainability and constitutes a key issue of both UE institutions and scientific ecological community. UE Water Framework Directive summarized the ‘state of the art’ of aquatic ecosystem monitoring and asked for scientific and technological innovations. The crucial point is the development of more effective ecosystem health descriptors. Nowadays, standardized descriptors are mainly chemical ecosystem features, which may be not representative at all of health condition of ecological community and biological indices and indicators, which either have low sensitivity to stress or are conceptually restricted to specific application. An innovative approach to environmental policy, including ecological research as a component of economic plans, and a stronger connection of applied research to basic ecological theories, are required to address some of the major gaps existing in the actual knowledge on monitoring aquatic ecosystem health and to improve sustainability of water resource management both in WBC and in the UEC
Spatial analysis of plant detritus processing in a Mediterranean River type: the case of the River Tirso Basin, Sardinia, Italy
No full textThe river continuum concept represents the most general framework addressing the spatial variation of both structure and function in river ecosystems. In the Mediterranean ecoregion, summer drought events and dams constitute the main sources of local disturbance to the structure and functioning of river ecosystems occurring in the river basin. In this study, we analyzed patterns of spatial variation of detritus processing in a 7th order river of the Mediterranean ecoregion (river Tirso, Sardinia – ITALY) and in three 4th order sub-basins which were exposed to different summer drought pressures. The study was carried out on Phragmites australis and Alnus glutinosa leaf detritus at 31 field sites in seasonal field experiment. Detritus processing rates were higher for Alnus glutinosa than for Phragmites australis plant detritus. Processing rates of Alnus glutinosa leaves varied among seasons and study sites from 0.006 d-1 to 0.189 d-1 and those of Phragmites australis leaves ranged from 0.0008 d-1 to 0.102 d-1, with the lowest values occurring at sites exposed to summer drought. Seasons and sites accounted for a significant proportion of such variability. Alder detritus decay rates generally decreased with increasing stream order, while reed detritus decay rates generally increased on the same spatial gradient. Summer drought events affected these spatial patterns of variation by influencing significantly the decay rates of both plant detritus. The comparisons among and within sub-basins showed strong negative influence of summer drought on detritus processing rates. Similarly, in the entire river Tirso basin decay rates were always lower at disturbed than at undisturbed sites for each stream order; decay rates of reed detritus remained lower at those sites even after the end of the disturbance events, while alder decay rates recovered rapidly from the summer drought perturbations. The different recovery of the processing rates of the two leaves could also explain the different patterns of spatial variation observed between the two leaves
Demand Model Generation from Traces: Adaptive KDE Data-Driven Optimization
No full textNowadays IoT and big data technologies make it easy to collect a huge amount of precise data about geospatial mobility. This abundant data improves mobility systems' study and optimization by allowing the application of data-driven approaches to gather accurate mobility models. In this paper, we evaluate techniques based on the optimization of Kernel Density Estimation (KDE) for modelling and generalizing the observed spatial data. We show how traditional KDE models fail to generalize the information obtained from mobility datasets, if not properly tuned. This mostly comes from the heterogeneity of the data, which changes over time (e.g., day and night) and space (e.g., dense or suburban areas). These issues call for fine grained parameter tuning, which we solve by automatically finding the optimal parameters for classical and variable KDE (V-KDE) approaches. We extensively compare the models' errors in capturing the mobility patterns using car sharing data. Our results show how optimized KDE and V-KDE models can better capture mobility patterns than traditional KDE approaches, both in 2D (i.e., origin or destination only) or 4D (i.e., representing origin-destination matrices) scenarios. We offer our tool available as open-source as a python module
Struttura tassonomica e dimensionale delle guild di macroinvertebrati bentonici nelle Saline di Margherita di Savoia. Atti S.It.E.
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