The importance of being natural in a human‐altered riverscape: role of wetland type in supporting habitat heterogeneity and the functional diversity of vegetation

Abstract

1. Human activities have dramatically affected the status of river ecosystems, mainly by completely altering their natural dynamics. One of the main questions in this regard is: 'How do the origin (natural or artificial) and hydrology (lentic or lotic) of a riverine wetland influence its heterogeneity and the functional diversity of its vegetation?'2. To answer this question, data from 60 wetlands were collected along the Oglio River (northern Italy), ã 700 km 2 ecosystem that is a typically over-exploited plain. In order to perform a quantitative assessment of habitat heterogeneity and vegetation diversity, a hierarchical approach was applied to sample sites divided into four functional zones (FZs) according to distinct seasonal inundation patterns (persistently aquatic, riparian, seasonally emergent and lateral zones).3. Plant communities were randomly surveyed in each FZ by using five replicates of 4 m 2 plots for aquatic and herbaceous plant communities and five replicates of 64 m 2 plots for woody and shrub communities. Data on species cover were estimated by standard methods (geometric-centered scale) 4. The highest values of heterogeneity (FZs per site) and vegetation diversity (plant communities per site) were found in natural lentic sites, whereas natural lotic sites exhibited the lowest values. A clear dependence of plant community assets on wetland origin was detected, thereby confirming the close relationship between heterogeneity and vegetation diversity. 5. Present results highlight the fundamental role played by natural sites in maintaining aquatic and wetland vegetation diversity in human-altered riverscapes. The pivotal role of water level fluctuations in promoting the diversity and distribution of aquatic and hygrophilous vegetation also clearly emerges.

Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation

“…Nevertheless, their observations suggested the existence of a combined positive effect of both hydrology and habitat heterogeneity in providing optimal conditions for fish recruitment. Similarly, Piotti (2015, 2016) [285,286] confirmed the pivotal contribution of riverine natural lentic sites, including oxbow lakes, to preserve high values of heterogeneity (expressed in terms of physical complexity of water bodies) and vegetation diversity (plant communities per site) in heavily exploited floodplains. This reinforces the clear dependence of aquatic plant communities on aquatic ecosystem origin, thereby confirming the intimate relationships between heterogeneity and vegetation diversity and, therefore, with the inter-and intra-annual hydrological cycles of water bodies colonized.…”

Fragmentation and groundwater supply as major drivers of algal and plant diversity and relative cover dynamics along a highly modified lowland river

“…This is probably due to the fact that the vast majority of field studies have focused on the degradation sequences of aquatic vascular plants and macrophyte vegetation as opposed to the mechanisms underlying macrophyte self-maintenance or the ability of such mechanisms to modulate the physicochemical and hydro-geomorphological conditions of the colonized habitats (i.e. selectivity sensu Murtaugh, 1996) (Bolpagni et al, 2013;Azzella et al, 2014;Bolpagni and Piotti, 2016).…”

Connectivity and habitat typology drive CO2 and CH4 fluxes across land–water interfaces in lowland rivers

“…Changes in the redox conditions can deeply modify the greenhouse gas budget, for example, stimulating the CO 2 reduction to CH 4 , which is detrimental for the global warming (Brix, Sorrell, & Lorenzen, ; Wilson, Baldwin, Rees, & Wilson, ). The succession of the riverbed emersion and submersion can also regulate the vegetation growth, patterns, and complexity, with potential effects on nutrient and gas fluxes (Bolpagni, Bartoli, & Viaroli, ; Bolpagni & Piotti, , ; Predick & Stanley, ).…”