Enhanced Diversity at Network Nodes: River Confluences Increase Vegetation-Patch Diversity~!2010-03-22~!2010-04-30~!2010-07-07~!

Abstract

Although dendritic networks within ecosystems have typically been considered a special case of network topology, they have attracted a great deal of attention in recent years. These systems exhibit unique features in that both the nodes and branches provide distinct habitats. Within a river discontinuum context, river confluences, which are nodes of dendritic river networks, are hypothesised to have particular hydrodynamic traits that create heterogeneous habitats through a unique disturbance regime, although this hypothesis has not yet been tested. We tested this hypothesis using a vegetation data set collected from 14 river basin systems in Hyogo Prefecture, Japan. We compared vegetation-patch diversity between confluence and single-flow areas using hierarchical Bayesian models. Our results demonstrated greater vegetation-patch diversity in confluence areas compared to single-flow areas. Our findings support the hypothesis that confluences result in highly heterogeneous habitats. To the best of our knowledge, this is the first empirical report to demonstrate that river confluences have high vegetation-patch diversity. We conclude that network nodes play an important role in maintaining the biodiversity of river networks.

Simulating the role of connectivity in shaping stream insect metacommunities under colonization cycle dynamics

“…This finding is consistent with empirical results showing that more connected, confluent or central nodes harbor more species (Brown et al, 2011;Fernandes et al, 2004;Grenouillet et al, 2004;Hitt and Angermeier, 2008;Osawa et al, 2010) and is also in line with the idea that environmental filtering plays a major role in aquatic insect distribution mainly at local scale (Heino et al, 2015c).…”

Paddy fields located in water storage zones could take over the wetland plant community

“…In monsoon Asia, paddy fields originate mainly from the floodplain 24 , which is characterized by both spatial and temporal heterogeneity 25 . Floodplains provide substantial habitat variety for vegetation 26,27 . Thus, there is a variety of previous (original) habitat type/quality among current paddy fields as wetland habitat.…”

Differences in distribution patterns around river confluences among hydrophilic vegetation groups

“…Vegetation was mainly distributed within 50 m of the river line and each vegetation patch was input as digital polygon data into GIS (ArcGIS version 9.1; ESRI Co., Tokyo, Japan). For a more detailed description of the RNER data set, see Osawa et al (2010a).…”

“…Total vegetation area was positively associated with patch numbers of five vegetation groups (annual grass and forb, perennial grass and vine, and shrub vegetation) and with total area of perennial grass vegetation. One possible explanation for the positive relationship is that smaller vegetation areas are indicative of the intensification of artificial habitat alterations (Osawa et al 2010a). On the other hand, the patch numbers of willow and riparian forest vegetation were negatively correlated with vegetation area.…”