Abstract
The aim of this study was to test the effect of agricultural and forestry land use on the structure of mayfly assemblages in low-order streams. Twenty-nine headwater streams were investigated in the state of São Paulo. We analyzed 15 streams in pristine areas (mixed tropical rainforest, semideciduous forest and dense tropical rainforest), and 14 streams covered with sugarcane, eucalyptus and pasture. Mayfly richness obtained by rarefaction curves was higher in pristine areas (21 genera), especially in mixed and semideciduous forest when compared to land use (9 genera), where values were particularly low in sugarcane plantation (3 genera). The non-metric multidimensional scaling (NMDS) ordination showed clear difference in mayfly assemblages between land uses and pristine areas, supported by analysis of similarity (R=0.67, p=0.001). In partial redundancy analysis (pRDA), the environmental descriptors that best explained differences in assemblage structure were Riparian, Channel and Environmental Inventory (RCE) index score, percentage of fine sediment stream substrate, water pH and land elevation. Our results show that agricultural and forestry land use has a strong negative effect on the structure of mayfly assemblages. These results also support the use of mayflies as environmental indicators, as some genera were sensitive to changes in land use, while others responded to naturally occurring changes in the study area.
Highlights
Anthropogenic actions, such as change in land use, have influenced most ecosystems in the world, via alteration of assemblage structure, resulting in a loss of species diversity and disturbances that can alter ecosystem functions (Allan et al 2004).Environmental modifications such as habitat fragmentation and the removal and substitution of riparian forest, have a negative effect on the input of organic material, and change the composition of allochthonous material that constitutes the energy source, the shelter and the food of headwater streams biota (Dudgeon et al 2006, França et al 2009)
Pristine area streams had substrate composed mainly of boulders, gravel and sand and strong habitat diversity provided by the accumulation of leaves, while the streams in land use areas were characterized by homogeneous substrate
Our results reinforce the importance of riparian forest for mayfly richness
Summary
Anthropogenic actions, such as change in land use, have influenced most ecosystems in the world, via alteration of assemblage structure, resulting in a loss of species diversity and disturbances that can alter ecosystem functions (Allan et al 2004) Environmental modifications such as habitat fragmentation and the removal and substitution of riparian forest, have a negative effect on the input of organic material, and change the composition of allochthonous material that constitutes the energy source, the shelter and the food of headwater streams biota (Dudgeon et al 2006, França et al 2009). The increased extent of agricultural land in southeastern Brazil caused suppression of native forest, directly and negatively affecting water quality, physical habitat and biota of many streams (Corbi and Trivinho-Strixino 2008, Kleine et al 2012) In this region, there has been strong expansion of exotic monocultures such as pine and eucalyptus, used in the wood and paper industry, and sugarcane to produce sugar and fuel alcohol. In the state of São Paulo, natural forests (Atlantic rainforest) are found in fragmented areas, mainly in Conservation Units (CUs) that serve as ‘reference areas’, inserted in regions dominated by extensive monocultures and pastures
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