Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

Abstract

Summary Reduced‐impact logging (RIL) has been considered as the main activity of forestry management in the Amazon. However, little is known of the effects of RIL on the region's ecosystems or in their biodiversity, and such information would be useful to inform forest management. Accordingly, this study aimed to investigate the effects of RIL on physical habitat and fish assemblages in Eastern Amazonia streams. We predicted that changes caused by RIL affect stream habitat, leading to a loss of diversity and changes in species composition with a predominance of generalist species. We sampled 13 streams in basins dominated by native vegetation without evidence of logging activity (unlogged areas) and 23 in areas that had been logged at different times between 2001 and 2011. Stream physical habitat structure was characterized using a standardized protocol, and the abundance, richness and composition of fish assemblages were assessed. Biotic and abiotic data were compared between unlogged and logged areas, and among streams in areas with different logging years. The relationship between the stream habitat structure and fish assemblages was assessed using a distance‐based linear model using a forward procedure, followed by application of the Akaike information criterion. Variations in tree canopy cover, channel morphology, water temperature and dissolved oxygen and conductivity accounted for most of the differences in habitat characteristics between unlogged and logged areas. A total of 53 fish species was collected, belonging to 20 families and 6 orders. Fish abundances did not vary consistently between streams in unlogged areas and those that had undergone RIL, and showed minor evidence of species‐specific changes in response to logging years. Likewise, there were no obvious differences in species richness, composition and biomass between logged and unlogged sites, regardless of logging years. RIL in Eastern Amazonia is performed in compliance with technical guidelines, but this practice has resulted in changes in stream physical habitat. Nonetheless, in the headwater streams that we sampled, the effects of RIL on fish assemblages were minor.

Threshold responses of Amazonian stream fishes to timing and extent of deforestation

“…Reduced impact logging (RIL) (i.e., planned harvest focused on minimizing impacts on soil and remaining forest) has been touted as a land management strategy that could contribute to stream biodiversity conservation in watersheds targeted for extractive forest activities (Prudente et al 2017). However, some research indicates that selective logging can cause sudden changes in fish species richness and abundance, and that effects are detectable even 8 years after the logging event (Dias et al 2010).…”

Land cover, riparian zones and instream habitat influence stream fish assemblages in the eastern Amazon

“…Mean annual temperature is 27.2°C, and the mean annual precipitation is 1,800 mm, with rainfall well-distributed throughout the year and exceeding 50 mm even in the driest months (i.e., August through October; Watrin & Rocha, 1992). Most of the remaining forests are subjected to reduced-impact logging that aims to minimise damage to soil and forest, or conventional logging that involves minimal consideration of forest resilience (Prudente, Pompeu, Juen, & Montag, 2017). Presently, oil palm production is the main crop, but interest in sugarcane is increasing.…”

“…Presently, oil palm production is the main crop, but interest in sugarcane is increasing. Some of the sites sampled in this study were surveyed in previous studies (Benone et al, 2017;Ferreira, Begot, Prudente, Juen, & Montag, 2018;Juen et al, 2016;Prudente, Pompeu, & Montag, 2018;Prudente et al, 2017). Within our study region, conventional logging started in the 1970s, oil palm has been cultivated since the 1980s, and reducedimpact logging was established in 2000 under guidelines proposed by the mandatory forest management plan of the Brazilian Forest Code (Law 4.771/65;Brasil, 1965).…”

“…Presently, oil palm production is the main crop, but interest in sugarcane is increasing. Most of the remaining forests are subjected to reduced-impact logging that aims to minimise damage to soil and forest, or conventional logging that involves minimal consideration of forest resilience (Prudente, Pompeu, Juen, & Montag, 2017). Within our study region, conventional logging started in the 1970s, oil palm has been cultivated since the 1980s, and reducedimpact logging was established in 2000 under guidelines proposed by the mandatory forest management plan of the Brazilian Forest Code (Law 4.771/65;Brasil, 1965).…”

Is environmental legislation conserving tropical stream faunas? A large‐scale assessment of local, riparian and catchment‐scale influences on Amazonian fish

“…Very few studies have examined the consequences of human impacts on the heterogeneous Amazonian fish assemblages in small streams. As such, little is known about the responses of stream fauna to deforestation, agricultural intensification and other sources of forest degradation (Dias et al, 2010;Issues, 2002;Leitão et al, 2017;Prudente, Pompeu, Juen, & Montag, 2017).…”