Macrophyte species richness and composition are correlated with canopy openness and water depth in tropical floodplain lakes (original) (raw)
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Drivers of aquatic macrophyte community structure in a Neotropical riverine lake
Acta Oecologica, 2011
We explored the hypothesis that flood events and connectivity interact with local factors (biotic and abiotic) to drive changes in aquatic vegetation in a typical backwater lake connected to the River Paraná, Brazil. Over three years, we conducted quarterly surveys to analyse macrophyte composition and abundance, and environmental variables. In total 34 macrophyte species were recorded, with strong dominance of Eichhornia azurea. During periods of low water level, the lake vegetation was primarily structured by distance from the river. Total community abundance and emergent species diversity increased from the outer to the inner lake, while the opposite occurred for submersed and floating species. These changes were strongly associated with gradients of depth, slope, water transparency, oxygen and phosphorus. Two summer flood periods had different effects upon plants depending on flood features (e.g. intensity, duration) and location. Flood-pulses tended to reset the community, both in terms of species abundance and richness, and disrupt competitive processes. Flood disturbances likely governed interactions among facilitation and competition processes. While recovering from the major flood disturbance, E. azurea invested strongly in stem horizontal growth, but less so in leaf production. In this situation the physical structure of E. azurea facilitated colonization by several other macrophyte species, resulting in substantial and rapid increase in species richness. Under a more stable hydrology E. azurea displaced less competitive species by forming dense stands. Connectivity and flood-pulses were the main factors responsible for sustaining high diversity of aquatic macrophytes in the lake, but these drivers interact, in both time and space, with local environmental and biotic drivers to structure the temporally and spatially shifting mosaic of lake vegetation. Our results show the fundamental importance of natural variability of hydrological connectivity and flood disturbances for biodiversity conservation in tropical riverine floodplains.
Temporal and spatial patterns of aquatic macrophyte diversity in the Upper Paraná River floodplain
Brazilian journal of biology = Revista brasleira de biologia, 2009
Although the importance of long-term data has been emphasized by ecologists in recent years, little is known about how communities may change over time. In this study, we describe the general patterns of aquatic macrophyte diversity in the Paraná River floodplain observed during six years of study. Temporal changes in community composition were also evaluated. Data on the presence or absence of aquatic macrophytes were collected between March 2002 and March 2008, in six lakes associated with three rivers. Different analytical strategies were used to evaluate the dynamics of aquatic macrophyte communities between the different systems in the floodplain. The composition of aquatic macrophytes differed among the rivers, mainly with respect to the different vegetation life forms (floating, submersed, emergent and rooted with floating stems). The temporal similarity of species composition during the six years and the beta-diversity index indicated that the month-to-month species turnover...
The structure of aquatic macrophyte assemblages can be affected by myriad factors, including physical, chemical and morphometric characteristics. We describe the patterns of plant species diversity and composition and vegetation height in aquatic ecosystems and their potential determinants at a regional scale in the Middle Paraná River floodplain. Sampling was conducted in twenty-three water bodies, including secondary channels, connected lakes and disconnected lakes. We compared the macrophyte species richness, composition and vegetation height in water bodies with different degrees of connectivity with the river and assessed the most important abiotic explanatory variables (morphometric, physical and chemical) associated with these assemblage attributes. Species accumulation curves showed that species richness did not differ between water bodies with different degrees of connectivity, although it tended to be lowest in secondary channels. Species richness was specifically associated with depth, conductivity, percent of solar radiation reaching the bottom and nitrate. Macrophyte assemblage composition was related primarily to the degree of connectivity, as rare species mostly occurred in disconnected lakes. Composition was also related to the degree of wind exposure (fetch), distance to shoreline and depth. Finally, vegetation height (a surrogate for biomass) was associated with the ammonium and sediment organic matter. Thus, a combination of morphometric and abiotic factors explained species richness, while degree of connectivity and morphometry explained assemblage composition. Vegetation height was explained by nutrients. These results suggest that a single set of variables is not sufficient to explain different aspects of macrophyte assemblages.
Species richness and ß-diversity of aquatic macrophytes in the Upper Paraná River floodplain
Fundamental and Applied Limnology, 2001
In this paper, we estimated the aquatic macrophyte species richness in the Upper Parana River floodplain using non-parametric estimators. Fifty species were recorded in intensive surveys of several floodplain habitats. Based on a random sample of 20 lagoons, 6 connected to the Parana River, 6 to one tributary and 8 to another, all estimators gave values very similar to the "true" number of species recorded in inten sive surveys. The comparison among the lagoons connected with these rivers showed that the species richness was different, after controlling for sampling effort. Corre spondence analysis and Mantel 's test showed that the beta diversity was significantly higher among the groups of lagoons than within groups of lagoons connected with the same river. The high connectivity among the lagoons of the same river can account for such results. Within the groups of lagoons, the highest species turnover (beta diversity) was found for Parana River lagoons, which are predominantly temporary and more variable. This result is in accordance with a general ecological prediction, which stres ses that beta diversity should increase with environmental variability.
Frontiers in plant science, 2018
Macrophyte assemblages are composed of species with different life forms and various ecological functions. Our aim was to investigate the potential environmental determinants of changes in the biomass of individual life forms and of the composition of the macrophyte assemblage in terms of life forms diversity. We sampled 23 waterbodies at low and high water levels in the Middle Paraná River floodplain. Macrophyte biomass samples were collected and classified in terms of life forms. We performed a redundancy analysis using the biomass of the various life forms to assess the importance of environmental variables to the composition of macrophyte life forms. Linear regressions were applied to investigate the environmental determinants of the biomasses of individual life forms. The degree of connectivity and the combination of depth, hydrology and nitrate were the main determinants of the composition in terms of life forms. The biomass of each individual life form was explained by differ...
Temporal and spatial patterns of aquatic macrophyte diversity in the Upper Paran� River floodplain
Braz J Biol, 2009
Although the importance of long-term data has been emphasized by ecologists in recent years, little is known about how communities may change over time. In this study, we describe the general patterns of aquatic macrophyte diversity in the Paraná River floodplain observed during six years of study. Temporal changes in community composition were also evaluated. Data on the presence or absence of aquatic macrophytes were collected between March 2002 and March 2008, in six lakes associated with three rivers. Different analytical strategies were used to evaluate the dynamics of aquatic macrophyte communities between the different systems in the floodplain. The composition of aquatic macrophytes differed among the rivers, mainly with respect to the different vegetation life forms (floating, submersed, emergent and rooted with floating stems). The temporal similarity of species composition during the six years and the beta-diversity index indicated that the month-to-month species turnover was, in general, lower in the connected lakes, which are directly influenced by the river. Probably the water level fluctuation is a selective force that contributes to maintaining diversity or richness. Our findings indicated the importance of abiotic characteristics and connectivity of the lakes in determining macrophyte composition and community stability over a long time frame.
Aquatic Botany, 2022
Spatial and temporal variation in limnological variables, as well as local changes in the hydrological pattern, may affect inundation hydrology and alter biotic interactions and functional diversity of aquatic macrophyte communities in the Pantanal. The objectives of this research in the floodplain along the Paraguay River were to: 1) examine changes in the diversity of aquatic macrophyte communities over a ten-year period based on surveys taken in 2008 and 2018; and 2) evaluate the possible indirect relation of changes in rainfall patterns, which in turn affect lateral hydrological connectivity and limnological variables that directly affect the composition and productivity of the aquatic macrophyte community. Comparison of data taken in 2008 and 2018 revealed a change in the timing and a reduction in the number of rainy days. These changes in rainfall patterns coincided with limnological changes, including increases in transparency, pH, dissolved oxygen, ammonium, nitrate, total nitrogen, orthophosphate, and total phosphorus, as well as decreases in water temperature and connectivity. Species richness of aquatic macrophyte communities in three ecological zones of the Paraguay River floodplain increased between 2008 and 2018, with increases in emergent grasses, emergent non-grasses, and amphibious life forms, showing a trend that favors species that are more adapted to drought conditions. The seasonal pattern of inundation and desiccation, as well as dissolved oxygen and temperature, where correlated with macrophytes communities variations. The colonization and expansion of rooted emergent macrophytes over this period could be a response to local anthropogenic activities, hydrological trends, or may reflect interannual rainfall variability.
Journal of Vegetation Science, 2018
QuestionsUnderstanding the processes that determine the variation in community composition (β‐diversity) is a major challenge in ecology, evolution, and conservation. Here we assess the importance of abiotic variables associated with local environmental features, hydrogeomorphology, and space to explain β‐diversity patterns in macrophytes by addressing the following questions: (1) Which are the sets of environmental, hydrogeomorphological, and spatial variables that contribute significantly to the spatial variation of macrophytes? (2) Which are their relative contributions to explaining the total β‐diversity, nestedness and turnover of macrophyte assemblages?Study SiteMiddle Paraná River floodplain, Argentina.MethodsWe sampled 20 lakes at low and high water levels in the Middle Paraná River floodplain. To investigate the relationship of total β‐diversity, turnover and nestedness with explanatory variables, we used the constrained analysis of principal coordinates (CAP). We used vari...