Functional Redundancy in bird community decreases with riparian forest width reduction

Abstract

Riparian ecosystems are suffering anthropogenic threats that reduce biodiversity and undermine ecosystem services. However, there is a great deal of uncertainty about the way species composition of assemblages is related to ecosystem function, especially in a landscape fragmentation context.Here, we assess the impact of habitat loss and disturbance on Functional Diversity (FD) components Functional Redundancy (FRed), Functional Evenness (FEve), and Functional Richness (FRic) of riparian forest bird assemblages to evaluate (a) how FD components respond to riparian forest width reduction and vegetation disturbance; (b) the existence of thresholds within these relationships; (c) which of the main birds diet guild (frugivores, insectivores, and omnivores) respond to such thresholds. We predict that FD components will be affected negatively and nonlinearly by riparian changes. However, guilds could have different responses due to differences of species sensitivity to fragmentation and disturbance. We expect to find thresholds in FD responses, because fragmentation and disturbance drive loss of specific FD components.Our results show that FRed and FEve were linearly affected by width and disturbance of riparian habitats, respectively. FRed was significantly lower in riparian forests assemblages below 400 m wide, and FEve was significantly higher above 60% disturbance. These responses of FD were also followed to the decline in insectivores and frugivores richness in riparian forests most affected by these changes.Consequently, our study suggests communities do not tolerate reduction in riparian forest width or disturbance intensification without negative impact on FD, and this becomes more critical for riparian area <400‐m wide or with more than 60% disturbance. This minimum riparian width required to maintain FRed is greater than the minimum width required for riparian forests by Brazilian law. Thus, it is important to consider mechanisms to expand riparian habitats and reduce the disturbance intensity in riparian forests so that riparian bird community FD may be effectively conserved.

Vegetation structure drives taxonomic diversity and functional traits of birds in urban private native forest fragments

“…Insectivorous and omnivorous birds prevailed, as has been reported several times for urban areas (Chace and Walsh 2006;MacGregor-Fors 2008;Ortega-Álvarez and MacGregor-Fors 2011;Domínguez-López and Ortega-Álvarez 2014;Pena et al, 2017;Barbosa et al 2020). On the other hand, the present results agree with other studies developed in forested areas regarding the predominance of species with functional traits with some dependence on forest resources, such as mixed and understory foraging stratum and intermediate forest-dependence (e.g., riparian, Domínguez-López and Ortega-Álvarez 2014;Batisteli et al 2018;Maure et al 2018). The urban greenspaces studied here are forested (Online Resource 1a), which favors forestdwelling species that require specific resources in these urban landscapes.…”

Environmental structure affects taxonomic diversity but not functional structure of understory birds in the southwestern Brazilian Amazon

“…Other studies have found an influence of habitat in functional metrics of forest bird assemblages. However, these studies have evaluated strong gradients of disturbance or environmental changes, for example, the effects of monoculture on Amazonian birds (Almeida et al 2016) and the reduction of riparian forest width on birds of the Atlantic Forest (Maure et al 2018). We suggest that environmental differences among our plots were not strong enough to generate major changes in functional structure of the assemblages.…”

Artisanal mining impacts small mammals while chainsaw milling is a more sustainable practice in Ghana

“…Differences in dietary guild composition observed across the different disturbance categories in forests, provide initial indications that omnivores may cope well under disturbance pressures. Vulnerability of some dietary guilds may explain the varying functional group compositions observed in human-altered forest sites (Luke et al 2014;Maure et al 2018). Given that most species in our study were omnivores and there was only one insectivore (large-headed shrew) and one herbivore species (typical striped grass mouse), no general statement about these two more specialized dietary guilds can be made.…”