... Finalmente, (4) se ha elaborado un mo-delo conceptual jerárquico como base para un modelo pre... more ... Finalmente, (4) se ha elaborado un mo-delo conceptual jerárquico como base para un modelo predictivo de la composición de las co ... de la inundación y fluctuaciones del nivel del agua después de la construcción de la presa en 1992 (GACIA & BALLESTEROS 1996; 1998). ...
ABSTRACT The study of the relationships between vascular aquatic macrophyte occurrence, species r... more ABSTRACT The study of the relationships between vascular aquatic macrophyte occurrence, species richness and the local environment are central for suitable ecosystem quality assessments, freshwater bodies management and assistance for macrophyte restoration. Here we quantify the importance of the local factors, both water column and sediment, to provide tools for lentic water systems management and conservation in a Mediterranean region. We surveyed 90 water bodies along a 2500 m altitudinal gradient in Catalonia (NE Spain). Despite its relatively small scale, the area of study exhibits large-scale environmental gradients mainly related to a diverse geology and climate. In consequence, the response of aquatic macrophytes to a broad range of environmental conditions can be studied without interference of biogeographical clines. We identified all vascular aquatic macrophytes and analyzed 35 environmental variables at each site. Local environmental factors accounted for only 19% of variance in aquatic macrophyte distribution. Even though water column variables explained more variance than sediment variables in a variance partitioning analysis (pCCA), a mixed model integrating variables of both compartments performed better. The most important variables driving aquatic macrophyte distribution were water conductivity, water DOC, water K, water pH, water Na, sediment organic matter, sediment Na and water nitrate. CCA between species and water and sediment variables clearly segregated coastal lagoons, temporary pools and alpine lakes over two main gradients: ionic content and water body productivity. Species richness was low (4.2 species per water body on average) and GAM showed weak correlations with sediment and most water column variables. The best factor explaining species richness was the geomorphological typology, but only temporary pools were significantly different from the other types and had the highest species richness. Thus, temporary pools were unique and displayed a high biodiversity, strengthening the need for their preservation.
ABSTRACT Even though aquatic macrophytes are key species in freshwater bodies and some of them ar... more ABSTRACT Even though aquatic macrophytes are key species in freshwater bodies and some of them are rare and vulnerable, aquatic macrophytic vegetation in the Mediterranean area is poorly known. Here we aim at identifying diversity patterns, both at the species and vegetation levels, from Catalonia (NE Spain), an area which holds a rich variety of aquatic ecosystems situated along a wide altitudinal range. More than 20,000 citations concerning 120 aquatic vascular plant species and 235 phytosociological relevés are studied. Data are obtained mainly from the Biodiversity Data Bank of Catalonia (BDBC) plus unpublished records. Aquatic macrophytes are present in 94% of the total 10 × 10 km2 UTM squares covering the studied area and 82% of the aquatic macrophytes reported from the Iberian Peninsula are listed in Catalonia. This illustrates that species richness in this small area is high, in accordance with its geomorphological and water body diversity. Coastal wetlands, deltas and alpine lakes arise as diversity hot spots, with altitude being a major factor in determining species distribution and richness. DCA ordination of the BDBC relevés also showed a high relevé dispersion for some submerged macrophyte associations like Potametum denso-nodosi, which can be explained either by inaccuracy when defining the association or by an erroneous identification of some relevés. Moreover, the compiled relevés come from a 8% of the studied territory, indicating that much effort has to be devoted to the study of these communities and their distribution.
ABSTRACT Distribution of aquatic macrophytes in lakes is related to geographical, morphological, ... more ABSTRACT Distribution of aquatic macrophytes in lakes is related to geographical, morphological, catchment and water chemistry variables as well as human impacts, which modify the original environment. Here, we aim at building statistical models to establish the ecological niches of 11 aquatic macrophytes (10 different phanerogams and the genus Nitella) from oligotrophic soft-water lakes and infer their ecological requirements and environmental constraints at the southernmost limit of their distribution. Macrophyte occurrence and environmental variables were obtained from 86 non-exploited oligotrophic soft-water lakes from the Pyrenees (Southern Europe; 42º50´N, 1º00´E); macrophytes inhabited 55 of these lakes. Optimum ranges and macrophyte occurrence were predicted in relation to 18 geographical, morphological, catchment and water chemistry variables using univariate and multivariate logistic models. Lakes at low altitude, in vegetated catchments and with low water concentration of NO3 - and SO4 -2 , were the most suitable to host macrophytes. In general, individual species of aquatic macrophytes showed clear patterns of segregation along conductivity and pH gradients, although the specific combination of variables selected in the best models explaining their occurrence differed among species. Based on the species response to pH and conductivity, we found Isoetes lacustris have its optimum in waters with low conductivity and pH (i.e. negative monotonic response). In contrast, Callitriche palustris, Ranunculus aquatilis, Subularia aquatica, Nitella spp., and Myriophyllum alterniflorum showed an optimum at intermediate values (i.e. unimodal response), whereas Potamogeton berchtoldii, Potamogeton alpinus, and Ranunculus trichophyllus as species had their optimum at relatively high water pH and conductivity (i.e. positive monotonic response). This pattern has been observed in other regions for the same species, although with different optima and tolerance ranges. The parsimonious models developed here allowed us to explore niche requirements for each species and to predict the occurrence of macrophytes and of individual species in any particular lake by using only few, easily measured environmental variables. This is of interest to forecast possible changes related to global change and to assist managers in making conservation, management and restoration decisions.
... Finalmente, (4) se ha elaborado un mo-delo conceptual jerárquico como base para un modelo pre... more ... Finalmente, (4) se ha elaborado un mo-delo conceptual jerárquico como base para un modelo predictivo de la composición de las co ... de la inundación y fluctuaciones del nivel del agua después de la construcción de la presa en 1992 (GACIA & BALLESTEROS 1996; 1998). ...
ABSTRACT The study of the relationships between vascular aquatic macrophyte occurrence, species r... more ABSTRACT The study of the relationships between vascular aquatic macrophyte occurrence, species richness and the local environment are central for suitable ecosystem quality assessments, freshwater bodies management and assistance for macrophyte restoration. Here we quantify the importance of the local factors, both water column and sediment, to provide tools for lentic water systems management and conservation in a Mediterranean region. We surveyed 90 water bodies along a 2500 m altitudinal gradient in Catalonia (NE Spain). Despite its relatively small scale, the area of study exhibits large-scale environmental gradients mainly related to a diverse geology and climate. In consequence, the response of aquatic macrophytes to a broad range of environmental conditions can be studied without interference of biogeographical clines. We identified all vascular aquatic macrophytes and analyzed 35 environmental variables at each site. Local environmental factors accounted for only 19% of variance in aquatic macrophyte distribution. Even though water column variables explained more variance than sediment variables in a variance partitioning analysis (pCCA), a mixed model integrating variables of both compartments performed better. The most important variables driving aquatic macrophyte distribution were water conductivity, water DOC, water K, water pH, water Na, sediment organic matter, sediment Na and water nitrate. CCA between species and water and sediment variables clearly segregated coastal lagoons, temporary pools and alpine lakes over two main gradients: ionic content and water body productivity. Species richness was low (4.2 species per water body on average) and GAM showed weak correlations with sediment and most water column variables. The best factor explaining species richness was the geomorphological typology, but only temporary pools were significantly different from the other types and had the highest species richness. Thus, temporary pools were unique and displayed a high biodiversity, strengthening the need for their preservation.
ABSTRACT Even though aquatic macrophytes are key species in freshwater bodies and some of them ar... more ABSTRACT Even though aquatic macrophytes are key species in freshwater bodies and some of them are rare and vulnerable, aquatic macrophytic vegetation in the Mediterranean area is poorly known. Here we aim at identifying diversity patterns, both at the species and vegetation levels, from Catalonia (NE Spain), an area which holds a rich variety of aquatic ecosystems situated along a wide altitudinal range. More than 20,000 citations concerning 120 aquatic vascular plant species and 235 phytosociological relevés are studied. Data are obtained mainly from the Biodiversity Data Bank of Catalonia (BDBC) plus unpublished records. Aquatic macrophytes are present in 94% of the total 10 × 10 km2 UTM squares covering the studied area and 82% of the aquatic macrophytes reported from the Iberian Peninsula are listed in Catalonia. This illustrates that species richness in this small area is high, in accordance with its geomorphological and water body diversity. Coastal wetlands, deltas and alpine lakes arise as diversity hot spots, with altitude being a major factor in determining species distribution and richness. DCA ordination of the BDBC relevés also showed a high relevé dispersion for some submerged macrophyte associations like Potametum denso-nodosi, which can be explained either by inaccuracy when defining the association or by an erroneous identification of some relevés. Moreover, the compiled relevés come from a 8% of the studied territory, indicating that much effort has to be devoted to the study of these communities and their distribution.
ABSTRACT Distribution of aquatic macrophytes in lakes is related to geographical, morphological, ... more ABSTRACT Distribution of aquatic macrophytes in lakes is related to geographical, morphological, catchment and water chemistry variables as well as human impacts, which modify the original environment. Here, we aim at building statistical models to establish the ecological niches of 11 aquatic macrophytes (10 different phanerogams and the genus Nitella) from oligotrophic soft-water lakes and infer their ecological requirements and environmental constraints at the southernmost limit of their distribution. Macrophyte occurrence and environmental variables were obtained from 86 non-exploited oligotrophic soft-water lakes from the Pyrenees (Southern Europe; 42º50´N, 1º00´E); macrophytes inhabited 55 of these lakes. Optimum ranges and macrophyte occurrence were predicted in relation to 18 geographical, morphological, catchment and water chemistry variables using univariate and multivariate logistic models. Lakes at low altitude, in vegetated catchments and with low water concentration of NO3 - and SO4 -2 , were the most suitable to host macrophytes. In general, individual species of aquatic macrophytes showed clear patterns of segregation along conductivity and pH gradients, although the specific combination of variables selected in the best models explaining their occurrence differed among species. Based on the species response to pH and conductivity, we found Isoetes lacustris have its optimum in waters with low conductivity and pH (i.e. negative monotonic response). In contrast, Callitriche palustris, Ranunculus aquatilis, Subularia aquatica, Nitella spp., and Myriophyllum alterniflorum showed an optimum at intermediate values (i.e. unimodal response), whereas Potamogeton berchtoldii, Potamogeton alpinus, and Ranunculus trichophyllus as species had their optimum at relatively high water pH and conductivity (i.e. positive monotonic response). This pattern has been observed in other regions for the same species, although with different optima and tolerance ranges. The parsimonious models developed here allowed us to explore niche requirements for each species and to predict the occurrence of macrophytes and of individual species in any particular lake by using only few, easily measured environmental variables. This is of interest to forecast possible changes related to global change and to assist managers in making conservation, management and restoration decisions.
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Papers by E. Chappuis