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Abstract High rates of deforestation, either in the past or the present, affect many of the ecological processes in streams. Integrating deforestation history and the current landscape structure enhances the evaluation of ecological effects of land-use change. This is especially true when contemporary landscape conditions are similar but the temporal path to those conditions differs. One approach that has shown promise for evaluating biodiversity responses over time and space is the β-diversity partitioning, which combines taxonomic and functional trait-based approaches. We tested hypotheses related to stream fish assemblages’ turnover in watersheds with different environmental conditions and deforestation histories. We sampled fish from 75 watersheds in the Machado River basin, Brazil, and environmental factors were quantified at multiple scales. Taxonomic turnover was higher than expected by chance, whereas functional turnover was lower than expected by the observed taxonomic turnover, indicating that deterministic processes are structuring these assemblages. The turnover, and the environmental factors differed among watersheds with different deforestation histories. Besides being scale-dependent, turnover patterns are also likely dependent on land use dynamics and involve time-lags.

Sugarcane and cattle pastures are two of the most widespread and economically important agricultural landscapes. However, in Brazil, they have not been properly investigated for their importance to native birds and wildlife conservation. Thus, we aim to characterize and compare bird assemblages of sugarcane and cattle pastures; and understand how landscape features within both habitats influence bird assemblages. We surveyed birds in both agricultural habitats over one year, and then investigated the relationship between species richness and composition with landscape diversity, matrix permeability, and the size and distribution of natural forests close to both habitats. We observed 132 species in cattle pastures and only 72 in sugarcane (48% bird community similarity). We further evaluated the richness and relative abundance of avian ecological groups, including habitat specialists and habitat generalists, insectivores, omnivores, granivores and frugivores. All avian groups were higher in pastures, the habitat where landscape heterogeneity and number of scattered trees was higher. Our results show that overall increasing landscape heterogeneity favors an assemblage with higher richness and composed by species with more diverse ecological functions. Therefore, we argue in favor of management practices that incorporate heterogeneity in agricultural landscapes, mainly in sugarcane fields where a homogeneous scheme has been used. Otherwise, the potential of agricultural landscapes for bird conservation will be highly hindered, particularly if the sugarcane sector expands to other agricultural lands.

Knowledge of soil hydraulic properties after forest restoration is essential for understanding the recovery of hydrological processes, such as water infiltration. An increase of forest cover may improve water infiltration and soil hydraulic properties, but little is known about the response and extent to which forest restoration can affect these properties. The purpose of this study was to investigate the effect of forest restoration on surface-saturated soil hydraulic conductivity (Ks), and to verify the Ks recovery to the pre-disturbance soil conditions. We sampled field Ks at the surface in Campinas municipality, São Paulo State, Brazil, at 18 plots under three land-cover types: (i) a pasture; (ii) a restored forest using a high-diversity mix of plantings (85 regional native species) of 9 years of age; and (iii) a remnant forest patch. We used the Beerkan method for soil hydraulic characterization. Bulk density (ρb), soil organic carbon content (OC), soil porosity and particle size data were also sampled. We found considerable differences in soil hydraulic properties between land-cover classes. The highest Ks were observed in remnant forest sites and the lowest Ks were associated with pasture sites. The Ks recovery differs markedly between restored forests. Our results strongly suggest that soil attributes and Ks recovery are influenced by the duration and intensity of land use prior to forest restoration. Attention needs to be given to management activities before, during and after forest restoration, especially where the soil is still compacted and Ks is low.

Agricultural land use is a primary driver of environmental impacts on streams. However, the causal processes that shape these impacts operate through multiple pathways and at several spatial scales. This complexity undermines the development of more effective management approaches, and illustrates the need for more in-depth studies to assess the mechanisms that determine changes in stream biodiversity. Here we present results of the most comprehensive multi-scale assessment of the biological condition of streams in the Amazon to date, examining functional responses of fish assemblages to land use. We sampled fish assemblages from two large human-modified regions, and characterized stream conditions by physical habitat attributes and key landscape-change variables, including density of road crossings (i.e. riverscape fragmentation), deforestation, and agricultural intensification. Fish species were functionally characterized using ecomorphological traits describing feeding, locomotion, and habitat preferences, and these traits were used to derive indices that quantitatively describe the functional structure of the assemblages. Using structural equation modeling, we disentangled multiple drivers operating at different spatial scales, identifying causal pathways that significantly affect stream condition and the structure of the fish assemblages. Deforestation at catchment and riparian network scales altered the channel morphology and the stream bottom structure, changing the functional identity of assemblages. Local deforestation reduced the functional evenness of assemblages (i.e. increased dominance of specific trait combinations) mediated by expansion of aquatic vegetation cover. Riverscape fragmentation reduced functional richness, evenness and divergence, suggesting a trend toward functional homogenization and a reduced range of ecological niches within assemblages following the loss of regional connectivity. These results underscore the often-unrecognized importance of different land use changes, each of which can have marked effects on stream biodiversity. We draw on the relationships observed herein to suggest priorities for the improved management of stream systems in the multiple-use landscapes that predominate in human-modified tropical forests.