Reduced riparian zone width compromises aquatic macroinvertebrate communities in streams of southern Brazil

Abstract

Recent changes in Brazilian legislation reduced the width of riparian forest buffer needed to be preserved in private properties from 30 to 15 m or less. The consequences of these modifications can be dramatic, mainly because riparian buffer width is an important parameter for riparian forest structure and functioning. Our study assessed whether (1) macroinvertebrate family richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) family richness decrease with reduced riparian buffer width; (2) taxonomic composition and functional feeding group (FFG) composition of macroinvertebrates vary with a reduced riparian buffer width; and (3) reduced riparian buffer width similarly influence the macroinvertebrate community in different stream substrates. We selected three fragments with different riparian buffer widths (>40, <30, and <15 m) in three streams (fourth and fifth orders) in the Sinos River watershed, southern Brazil. Our results show that on all substrate types, reducing the width of the riparian buffer altered neither the macroinvertebrate richness nor EPT richness. However, EPT richness was greater in the substrates stone and gravel than leaf litter, independent of riparian buffer width. There was a significant difference in macroinvertebrate composition among riparian buffer widths. The macroinvertebrate composition and FFG differed among substrates, independent of riparian buffer width. This study showed that riparian buffer widths <15 m altered the macroinvertebrate community. A width greater than 15 m is necessary to maintain the composition and trophic conditions of macroinvertebrate families similar to those found in reference states of conservation.

Effects of riparian vegetation width and substrate type on riffle beetle community structure

“…The inorganic or organic nature of substrate determined differences not only on dominant genera but also in riffle beetle community equitability. In other words, at least along short longitudinal gradients (basin scale), substrate type may overcome the importance of other environmental variables that can influence the diversity of stream insect communities, such as riparian vegetation width (Moraes et al ).…”

“…The role of the riparian vegetation in maintaining stream environmental integrity and conservation of aquatic communities is well documented (Rios & Bailey ; Couceiro et al ; Nessimian et al ; Lorion & Kennedy ; Iñiguez‐Armijos et al ). Previous studies show that larger riparian vegetation widths are required according to stream size in order to maintain their integrity (Rios & Bailey ; Lorion & Kennedy ; Iñiguez‐Armijos et al ; Moraes et al ). The Brazilian Forest Code also ensures that high‐order rivers have larger riparian vegetation widths, as in other countries (Lee et al ).…”

“…Because the sampling method varied among substrate types, samples used in the multivariate analyses were standardized by dividing the abundance of each genus in the sample by the total abundance of the sample ( sensu Moraes et al ). Non‐metric multidimensional scaling (NMDS) ordination diagrams were generated to assess the variation in larval and adult riffle beetle community structure among buffer strips and substrate types.…”

“…The results varied not only among targeted groups, but also among studies (e.g. Lee et al ; Marczak et al ; Moraes et al ). Differences in regional (e.g.…”

“…The critical point of this new legislation is that approximately 53% of Brazilian native vegetation occurs on private properties (Soares‐Filho et al ). Additionally, studies focusing the effects of riparian vegetation reduction on aquatic communities are insufficient to support conservation policies (Couceiro et al ; Nessimian et al ; Moraes et al ).…”