Riparian Deforestation Research Articles

Lower diversity in benthic macrofaunal assemblages associated with increasing riparian deforestation in first-order lowland tropical streams

ABSTRACT In aquatic ecosystems, benthic macroinvertebrates are strongly influenced by riparian habitat quality. We investigated associations between riparian deforestation, stream habitat variables and benthic macroinvertebrate assemblage structure, particularly sensitive taxa. We sampled macroinvertebrates and physical-chemical variables during both the dry and wet seasons at three sites, each with low, medium, and high levels of riparian deforestation, in each of three first-order streams in the lower zone of the Caeté river in eastern Amazonia, Brazil. The relationships were examined using Generalized Linear Mixed-Models (GLMM) and multivariate analysis. Macroinvertebrate families most associated with deforestation levels were determined by Indicator Species Analysis. We hypothesized that lower riparian deforestation is associated with greater diversity, especially of sensitive taxa, and lower dominance. A total of 3,427 macroinvertebrates distributed in 54 families were found, of which 25 were sensitive taxa. Sites with high deforestation, associated with Glossiphonidae, Tubificidae, and Naididae, differed from those with medium (associated with Limnephilidae) and low (associated with Polycentropodidae and Hydropsychidae) deforestation. Families and abundance of EPTC (Ephemeroptera, Plecoptera, Trichoptera, and Coleoptera) were lower at high deforestation, with significant losses of taxa compared to the whole assemblage. In Caeté headwaters, deforestation is an important factor for structuring benthic macroinvertebrate assemblages.

Open riparian canopy and nutrient pollution interactively decrease trophic redundancy and allochthonous resource in streams

Riparian deforestation, which leads to increase in light intensity and excessive nutrient loading in waterways, are two pervasive environmental stressors in the stream ecosystems. Both have been found to alter basal resource availability and consequently stream food webs. However, their interactive effects on trophic structure in stream food webs are unclear. Here, we manipulated light intensity and nutrient availability in three headwater streams to evaluate their effects on consumer diet composition and food web characteristics (i.e., trophic diversity and redundancy) with stable isotope analysis. Dietary analysis revealed that the relative contribution of stream periphyton to the diets of macroinvertebrates increased, while that of allochthonous resources, specifically leaf litter from the terrestrial ecosystems in the catchment, decreased in response to open canopy and nutrient enrichment in the streams. The trophic diversity also increased with the elevated light intensity and nutrient availability, while the trophic redundancy decreased, suggesting a reduced ability of the stream ecosystems to resist environmental changes. Nutrient enrichment also increased the δ15N ratios of periphyton and macroinvertebrates, indicating potential δ15N enrichment of stream benthos by nitrogen pollution. Our results suggested that an increase in light intensity due to riparian canopy openness and stream water nutrient enrichment primarily from human activities have interactive effects on resource flow and trophic structure in stream food webs.

Pressões humanas degradam a condição ecológica do Alto Ribeirão Graipu

ABSTRACT Environmental degradation from human pressures includes the conversion of native vegetation cover into pastures and cropland, as well as riparian deforestation, leading to river siltation, biotic homogenization, and loss of ecosystem services. The objective of our study was to evaluate water quality and benthic macroinvertebrate assemblage structure in response to changes in land use at local and buffer spatial extents. We assumed that human disturbances negatively affect water quality and macroinvertebrate assemblage condition. Greater human influence was observed at the local extent (Local Disturbance Index – LDI) than at the buffer (Buffer Disturbance Index – BDI) extent. Likewise, biological metric responses were stronger relative to the LDI than to the BDI or to the Integrated Disturbance Index (IDI). These results support establishing a biomonitoring program for assessing water body quality in the Doce River basin to facilitate conserving aquatic biodiversity and ecosystem services in the upper Graipu River.

HILL STREAM ICHTHYOFAUNAL DIVERSITY OF BAKSA DISTRICT ALONG THE INTERNATIONAL BORDER BETWEEN INDIA AND BHUTAN: ECONOMIC IMPORTANCE AND ANTHROPOGENIC THREATS

North-Eastern states are leaders in the diversity of indigenous species of economically important fish. Hill streams of this region inhabit ichthyofauna of broad importance. However, increased anthropogenic activity possess deleterious consequence. The goal of the study conducted from January 2021 to July 2022 was to document and report the ichthyofaunal diversity of the hill streams in the Baksa district of Assam, India, its economic importance as well as potential threats associated with it. A total of 3182 fishes classified into 39 species, 13 families, and 5 orders were documented. Cypriniformes is the dominant order (71.24%), followed by Perciformes (17.76%), Siluriformes (5.97%), Symbranchiformes (3.65%), and Beloniformes (1.38%). These hill streams inhabit endangered, vulnerable, near-threatened, lower-risk-near-threatened species (IUCN, CAMP, and ICAR). Diversity indices indicate that these streams are rich in evenly distributed ichthyofauna. However, the recent spike in riparian deforestation, illegal fishing, and tourism-related plastic garbage possess a serious threat to these hill-stream ecosystems and inhabiting fish fauna. The consequences of riparian deforestation are looming as a severe future issue. Conservation of this ecosystem has become an important call to take on.

Spatiotemporal diet shifting in a neotropical fish species: The role of riparian vegetation and seasonal inundation

Aquatic organisms that consume resources from riparian vegetation or floodplain forests act as trophic links between aquatic and terrestrial ecosystems. For instance, the pacu Piaractus mesopotamicus (Holmberg 1887), which is a migratory fish species, can play an important role in this interaction on Neotropical floodplains. We compared the stomach content of individuals from this species between two different parts of a large river floodplain during contrasting hydrological seasons to quantify the spatiotemporal contribution of allochthonous and autochthonous resources in their diet. Moreover, we performed a bipartite network approach to evaluate the sensitivity of these populations to a simulated loss of food resources through the potential deforestation of riparian vegetation. We found that in the upper catchment, individuals fed mainly on allochthonous items, but their identity depended on the season: fruits were the most abundant resource during the wet season, whereas leaves were more consumed during the dry season. In the lower catchment, the contribution of allochthonous resources was slightly lower in the dry season than in the wet season, when the pacu was able to explore the floodplain. Finally, the results from our consumer-resource network model indicated that this system is vulnerable to riparian deforestation since P. mesopotamicus is highly dependent on input from the riparian vegetation items to its feed.

The role of environmental legislation and land use patterns on riparian deforestation dynamics in an Amazonian agricultural frontier (MT, Brazil)

Agribusiness expansion and intensification in Brazil have prompted an abrupt change in land use and occupation in the Amazonian agricultural frontier since the 1980s. Considering the increasing suppression of native vegetation, riparian areas represent an important tool for protecting ecosystem services and biodiversity. Although the effects of land tenure and land use on large-scale deforestation in the Amazon have been widely assessed, their roles on riparian deforestation remains poorly explored. Here we assessed two municipalities – Querência (QRC) and São José do Xingu (SJX) – located in an agricultural frontier of the Brazilian Amazon to explore the relationship of illegal deforestation in riparian areas and different types of land use and property-sizes, as well as the impact of the Native Vegetation Protection Law (NVPL, Federal Law 12,651/2012) on environmental compliance. Therefore, we developed a robust geodatabase using hydrographic, land use and land tenure data. Riparian areas protected as Permanent Preservation Areas (PPAs) were delimited and their land cover mapped for 2012 and 2018 using high spatial resolution satellite images and unsupervised K-means classification method. We also applied landscape metrics to analyze riparian PPA structure and dynamics. Our results indicated that NVPL was followed by a downward trend in the riparian vegetation deficits in all land use types and property-sizes, but it did not stop new clearings. Although riparian PPAs in minifundios (≤ 80 ha) and agrarian reform settlements tended to concentrate higher relative deforestation amounts, large-sized farms were responsible for most of the absolute extent of riparian deforestation in both years, accounting for 76–78% in QRC and 93% in SJX. They were also the main drivers of new clearings, for which account for 71% in QRC and 86% in SJX. The impact of land use on riparian deforestation was not homogeneous among properties, possibly reflecting different levels of technological investment and management techniques. In the so-called consolidated areas, in which the riparian PPA minimum width was reduced by NVPL, decreases in deforestation between 2012 and 2018 were lower. In these areas, vegetation coverage did not exceed 23% in any of the study areas. In the riparian PPAs that was not under consolidated areas, the vegetation coverage was of at least 85% of the area. Local environmental governance may also have affected the riparian deforestation dynamics, in which stricter monitoring and law enforcement lead to lower deforestation extents. Finally, landscape metrics revealed the importance of managing riparian areas at the landscape level, as local improvements did not necessarily result in connectivity gains.

Functional responses of Odonata larvae to human disturbances in neotropical savanna headwater streams

Headwater streams are facing increasing disturbances from human pressures worldwide, thus better knowledge about bioindicators, particularly aquatic insect responses to various pressures and stressors, are urgently needed. Multiple trait-based approaches consider species attributes filtered by the environment, allowing them to persist in ecosystems under environmental pressures. Because this approach has been minimally explored in Odonata larvae, we aimed to understand how anthropogenic stressors structure Odonata larval assemblages in neotropical savanna streams by using multiple trait-based approaches. We hypothesized that a set of stressors--such as reduced substrate heterogeneity, poor water quality, natural land cover converted to pasture and agriculture, and reduced local riparian canopy cover--select Odonata functional traits. We collected 3209 Odonata larvae from 186 neotropical savanna headwater stream sites and used 39 environmental variables and seven traits in 23 categories related to their functional roles in Odonata genera. To assess associations between trait categories and environmental variables, we applied RLQ and fourth-corner statistical analyses. We found strong relationships between environmental variables and sets of Odonata biological traits that were separated into two main groups. Zygoptera genera (Perilestes, Allopodagrion, Heliocharis, Argia, Epipleoneura, Mnesarete/Hetaerina, Psaironeura) have elongated body shapes, caudal lamellae respiration, conforming thermoregulation, and endophytic oviposition. Such traits favor assemblages in conditions similar to reference streams, including denser riparian vegetation, good water quality, and diverse flows and substrate. Therefore, they are more sensitive to changes in those conditions. On the other hand, Anisoptera genera (Gomphoides, Archaeogomphus, Macrothemis, Brechmorhoga, Gynothemis, Phyllocycla) have cylindrical body shapes, internal gill respiration, endothermic thermoregulation, and burrowing behavior. Those traits facilitate their survival in intermediate or disturbed stream sites, characterized by riparian deforestation, increased erosion and siltation, and higher levels of total dissolved solids and conductivity. Therefore, using Odonata larval traits can be a valuable tool for assessing and monitoring anthropogenic impacts on neotropical savanna streams.

The role of secondary riparian forests for conserving fish assemblages in eastern Amazon streams

Riparian deforestation degrades stream habitats, altering fish assemblages’ structure, and composition. In contrast, secondary riparian forests can recover stream habitats and fish assemblages as they recover structural attributes and ecological processes. We evaluated whether the amount and condition of secondary riparian forests were important to conserve fish assemblages in 49 streams sites in eastern Amazonia. We related fish assemblage taxonomic and functional measures to riparian forest amount plus different habitat metrics using regression analysis. We compared assemblage measures among reference forests, abandoned pastures (open canopy), and secondary forests (closed canopy) using ANOVA tests. The amount of secondary forests had little influence on fish assemblages. Species richness, diversity, and functional richness were higher in pasture than in reference sites but returned to pre-disturbance conditions in secondary sites. However, functional evenness was lower in pasture streams and did not recover after secondary forest regrowth. Our results show that secondary riparian forest condition is important to recover some aspects of fish assemblages. However, streams bordered by these forests may have impoverished fish assemblages because some lost sensitive species may take longer to return. Avoiding riparian deforestation is the best strategy to reduce losses in aquatic biodiversity and ecosystem functions in tropical agricultural landscapes.

Taxonomic and functional responses of macroinvertebrates to riparian forest conversion in tropical streams

Land use change threatens the ecological integrity of tropical rivers and streams; however, few studies have simultaneously analyzed the taxonomic and functional responses of tropical macroinvertebrates to riparian forest conversion. Here, we used community structure, functional diversity, and stable isotope analyses to assess the impacts of riparian deforestation on macroinvertebrate communities of streams in southern Mexico. Monthly sampling during the dry season was conducted in streams with riparian forest (forest streams), and in streams with pasture dominating the riparian vegetation (pasture streams). Samples were collected for water quality (physical-chemical variables, nutrient concentrations, and total suspended solids), organic matter (leaf litter abundance and algal biomass), and macroinvertebrate abundance and diversity. Higher temperature, conductivity, suspended solids, and chlorophyll a were detected in pasture streams, while nitrate concentrations and leaf litter biomass were greater in forest streams. Macroinvertebrate density was higher in pasture sites, while no differences in taxonomic diversity and richness were found between land uses. Functional evenness was greater in forest streams, while richness and divergence were similar between land uses, despite differences in taxonomic composition. Environmental variables were associated with taxa distribution but not with functional traits, suggesting current conditions still promote redundancy in ecological function. Isotopic analyses indicated consumers in pasture streams were enriched in 13C and 15N relative to forest streams, potentially reflecting the higher algal biomass documented in pasture systems. Isotopic niches were broader and more overlapped in pasture streams, indicating more generalist feeding habits. No significant losses of taxonomic or functional diversity were detected in pasture streams. However, changes in trophic ecology suggest landscape-level processes are altering macroinvertebrate feeding habits in streams. The changes we observed in habitat, water quality, and macroinvertebrate community were related to the removal of the riparian vegetation, suggesting the structure and function of the focal systems would benefit from riparian restoration.

Effects of riparian deforestation on benthic invertebrate community and leaf processing in Atlantic forest streams

Riparian deforestation may strongly affect stream functioning, with consequences for biodiversity and ecosystem services. These effects can be assessed using bioindicators relating to biotic community structure and ecosystem functioning. We evaluated the effects of riparian deforestation on 1. measures of community structure using aquatic benthic invertebrates, and 2. an aspect of ecosystem functioning, aquatic leaf processing. We selected sites along gradients of riparian land use in four Atlantic rainforest streams and measured physical and chemical properties for their association with riparian deforestation. We sampled benthic invertebrates and calculated metrics of community structure at each site. We measured rates of leaf processing using leaves of a common riparian tree, Guarea guidonia. Riparian deforestation was accompanied by increasing concentration of ammonia, water current and temperature and decreasing nightly oxygen saturation. Invertebrate diversity decreased and community metrics changed with deforestation as expected of negative impacts. Leaf processing decreased with deforestation. Although there were significant differences in physical and chemical measurements among streams, the gradients in community and ecosystem responses were similar, thus suggesting that both types of bioindicators were useful for monitoring changes and relating them to loss of biodiversity and ecosystem function.

Nutrient loadings and deforestation decrease benthic macroinvertebrate diversity in an urbanised tropical stream system

Lotic ecosystems in urban areas are severely impacted by anthropogenic environmental stressors, such as deforestation and nutrient pollution, due to socioeconomic activities in the catchment. To work out measures for identification and mitigation of concurrent multiple stressors to a stream system, it is necessary to assess the relative importance of impacts by the individual stressors. Here we aimed to discriminate the covarying effects of nutrient pollution and deforestation on benthic macroinvertebrate communities in an urbanised tropical stream system. In the Silang-Santa Rosa Subwatershed (SSRS) of Laguna de Bay, benthic macroinvertebrates and physicochemical environments were investigated at 13 sites varying in human population density, riparian canopy, and land-use pattern as indicated by geographic information systems in the catchment. Regression and multivariate analyses were performed to identify the drivers of the biodiversity loss and understand its underlying mechanisms. In the SSRS, where rapid economic growth took place without updating poorly installed wastewater treatment plants (WWTPs), domestic activity indicated by human population density in the catchment was the primary factor in generating heavy phosphorous loadings (mean total phosphorus = 0.91; range = 0–1.50 mg/l) that caused hypoxia (mean dissolved oxygen = 2.98; range = 0.13–6.27 mg/l) in stream waters and subsequently reduced macroinvertebrate diversity (mean H’ = 0.91; SD ± 0.61). Nutrient and organic pollution and riparian deforestation explained 53.5% and 9.7% of the variation of benthic macroinvertebrate communities in SSRS, respectively. Given such scenario, additional WWTPs servicing urban developments and improved riparian canopy cover in the SSRS can be both strategic and cost-effective in the initial steps of environmental mitigation in urbanised streams, especially in rapidly developing countries.

Removal of Woody Riparian Vegetation Substantially Altered a Stream Ecosystem in an Otherwise Undisturbed Grassland Watershed

Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds with a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.

Historic carbon burial spike in an Amazon floodplain lake linked to riparian deforestation near Santarém, Brazil

Abstract. Forests along the Amazon Basin produce significant quantities of organic material, a portion of which is deposited in floodplain lakes. Deforestation in the watershed may then have potentially important effects on the carbon fluxes. In this study, a sediment core was extracted from an Amazon floodplain lake to examine the relationship between carbon burial and changing land cover and land use. Historical records from the 1930s and satellite data from the 1970s were used to calculate deforestation rates between 1930 to 1970 and 1970 to 2010 in four zones with different distances from the margins of the lake and its tributaries (100, 500, 1000 and 6000 m buffers). A sediment accumulation rate of ∼4 mm yr−1 for the previous ∼120 years was determined from the 240+239Pu signatures and the excess 210Pb method. The carbon burial rates ranged between 85 and 298 gCm-2yr-1, with pulses of high carbon burial in the 1950s, originating from the forest vegetation as indicated by δ13C and δ15N signatures. Our results revealed a potentially important spatial dependence of the organic carbon (OC) burial in Amazon lacustrine sediments in relation to deforestation rates in the catchment. These deforestation rates were more intense in the riparian vegetation (100 m buffer) during the period 1930 to 1970 and the larger open water areas (500, 1000 and 6000 m buffer) during 1970 to 2010. The continued removal of vegetation from the interior of the forest was not related to the peak of OC burial in the lake, but only the riparian deforestation which peaked during the 1950s. Therefore, this supports the conservation priority of riparian forests as an important management practice for Amazon flooded areas. Our findings suggest the importance of abrupt and temporary events in which some of the biomass released by deforestation, especially restricted to areas along open water edges, might reach the depositional environments in the floodplain of the Amazon Basin.

EVALUATION OF HUMAN-ENVIRONMENT INTERACTION IN RIVER OMINLA RIPARIAN CORRIDOR IN ORE TOWNSHIP, ONDO STATE, SOUTH WESTERN NIGERIA

The study was aim to assess the condition resulted from riparian encroachment in the study area with a view to provide a baseline information for urban and surface water sustainable development. Primary and secondary data were employed. Primary data involved field survey using questionnaire in which 245 copies were administered to the selected riparian residents to evaluate their perception and experience on human effects on riparian vegetation, water body and resultant problems. Secondary data involved an existing relevant data. The data were analysed using descriptive statistics. The survey results showed that urban growth had resulted to loss of farmland/garden (73.9%), riparian natural forest (86.1%), medicinal tree/herbs and shrub (77.1%), and useful timbers (62.8%). Riparian deforestation had also resulted to high sedimentation of the river basin (77.6%), increased river seasonal volume (76.7%),enhanced access of solid particles/materials into the river (76.7%), loss of riparian animals (82.9%), pollution of the river (75.5%) riparian flooding (75.9%) that subsequently resulted to loss of lives and properties (84.1%) and loss of valuable plant (95.9%).Therefore, the study concluded that there is significant negative effects of anthropogenic activities on River Ominla Riparian corridor and that this requires urgent attention.

Does environmental disturbance also influence within-stream beta diversity of macroinvertebrate assemblages in tropical streams?

ABSTRACTRiparian deforestation is a major threat to the ecological integrity of streams and aquatic biodiversity, influencing microhabitat availability and susceptibility to disturbances. Here we tested if riparian deforestation of tropical streams influenced beta diversity of macroinvertebrate assemblages, by comparing indices that weighted differentially rare and dominant taxa, and testing if nestedness in community composition increased in deforested streams. Within-stream beta diversity was higher in deforested than forested streams, mainly due to taxon loss and higher dominance. In disturbed streams, higher sedimentation in pool mesohabitats resulted in larger differences in community composition, whereas mesohabitats in forested streams were more stable.

Modelling the effect of riparian vegetation restoration on sediment transport in a human‐impacted Brazilian catchment

AbstractSoil erosion threatens both soil and water resources and has increased globally because of the removal of natural vegetation and the intensification of existing agriculture. Brazil is privileged by a large proportion of natural vegetation and abundant freshwater. Recently, modifications of the Brazilian Forest Act (BFA) have been approved, which offer landowners that had committed illegal riparian deforestation in the past amnesty from reforestation, and further reductions of riparian protected areas are currently discussed. Here, we used the Soil and Water Assessment Tool to simulate river discharge and sediment exports in a typical human‐impacted Brazilian catchment, the Rio das Mortes catchment. By restoring the riparian vegetation according to the BFA and ignoring amnesties to land owners, the current annual sediment export of the catchment of 0·830 t ha−1 was reduced by 29·4% according to our model. Further, simulated reforestation twice the size demanded by the BFA resulted in a 31·4% reduction of the current sediment export. However, reforestation of a 5‐m homogeneous riparian corridor only, as currently discussed in the Federal Brazilian State of São Paulo, reduced sediment exports by only 23·8%, not considering expected additional erosion due to deforestation outside the simulated reforested 5‐m corridor. Our study is the first catchment‐wide assessment of the role of riparian vegetation in preventing soil erosion in Brazil. Its results support intensive reforestation efforts of the riparian zone and point to substantial negative effects of further reductions of the protected riparian corridor width and amnesties from reforestation to land owners. Copyright © 2016 John Wiley & Sons, Ltd.

Context-dependent responses to light contribute to responses by Black-bellied Salamanders (Desmognathusquadramaculatus) to landscape disturbances

Behaviour often regulates population responses to environmental change, but linking behavioural responses to population patterns can be challenging because behavioural responses are often context-dependent, have an instinctive component, and yet may be modified by experience. Black-bellied Salamanders (Desmognathus quadramaculatus (Holbrook, 1840)) occupy forested streams where dense canopies create cool, dark environments. Because riparian deforestation negatively affects salamander-population connectivity yet some individuals choose to persist in these gaps, we sought to evaluate whether phototaxis could explain these patterns and whether phototactic behaviour would be influenced by experience (capture from forested or deforested areas) or context (refuge type and availability). Our results demonstrated that larval D. quadramaculatus exhibited negative phototaxis, but that larvae from forested streams exhibited stronger negative phototaxis than individuals from deforested streams. Larvae also selected habitat closer to light when refuge was available. Our results show that light alters habitat use by larval D. quadramaculatus, but the magnitude of that effect depends on refuge availability and experience with well-lit conditions associated with forest removal. As human activities reduce canopy cover and refuge availability, negative phototaxis may be one explanation for behavioural barriers to movement. Ultimately, the ability of salamanders to exhibit behavioural plasticity will determine their potential for local adaptation facilitating persistence in the face of environmental change.

Influence of an exotic grass on benthic macroinvertebrate communities in a tropical rural landscape

Riparian deforestation in rural areas has led to changes in bankside vegetation communities that may have unexpected effects on stream ecosystems. In particular, plants such as grasses can colonize the streambed from adjacent terrestrial habitats, thus altering the physical structure of the streambed and potential influencing macroinvertebrate communities. Here we evaluated if the presence of patches of grasses (Urochloa sp.) on the streambed influenced the structure and composition of macroinvertebrate communities in deforested rural streams. We sampled patches with and without grasses in three low-order streams, in the wet and dry seasons. We recorded higher abundances of macroinvertebrates in patches with grasses in the wet season when compared with bare patches. We also found significant differences in taxonomic and functional feeding group composition between patch types, due to higher overall abundances in patches with grasses, probably due to more food and shelter there. These influences were stronger in the wet season, when in-stream grasses may have provided greater refugia from flood disturbance that occur with increased frequency and intensity. Therefore, although deforestation of rural streams can simplify streambed habitats, in-stream grasses such as Urochloa sp. provide resources that contribute for the maintenance of macroinvertebrate communities.

Autochthonous primary production in southern Amazon headwater streams: Novel indicators of altered environmental integrity

The riparian forest reduces the amount of light entering streams, which limits autochthonous primary production. The aim of this study was to evaluate temporal variation of autochthonous primary production in pristine and altered streams, with the goal of identifying indicators of change in environmental integrity in the southern Brazilian Amazon. We evaluated free algal biomass in the water column, the presence of periphyton, and the richness and cover of aquatic herbaceous plants in 20 streams (10 pristine and 10 altered, i.e., with riparian deforestation) during the dry period, at the beginning of the rainy period, and at the end of the rainy period. In altered streams, we recorded the presence of macroscopic periphyton and the amount of algal biomass varied between the dry and flood seasons. Variations in hydrological periods did not contribute to changes in algal biomass in pristine streams; we did not observe the presence of macroscopic periphyton these streams. In altered streams, 23 aquatic herbaceous species were identified, versus only four in the pristine streams. Results showed that riparian deforestation contributes to increased autochthonous primary production, which is also influenced by different hydrological periods, with algae and aquatic herbaceous plants responding differently to dry and rainy periods. The responses of these primary producers confirm their role as important bioindicators of change in the environmental integrity of southern Amazonian streams.

The effect of riparian deforestation on macroinvertebrates associated with submerged woody debris

Riparian deforestation is one of the main causes of change in freshwater ecosystems, resulting in the reduction of biological integrity and the loss of ecosystem functions. Our goal was to understand how a gradient of deforestation may affect abundance and richness of specialist and generalist macroinvertebrates associated with submerged woody debris in Neotropical streams. We conducted an observational study sampling mixed-species woody debris from 16 streams along a deforestation gradient. We also conducted an incubation study with known woody debris species (Cecropia pachystachya Trecul) in six streams. We collected 781 specimens and identified 50 taxa in the observational study, and we found 99 individuals belonging to 17 taxa in incubation study. Results from the two complementary studies indicate that the effect of riparian deforestation was more pronounced for wood specialists than generalists. Deforestation decreased the abundance and richness of wood specialists, and some taxa were locally extinct. The incubation study showed that sedimentation, which leads to the burying of woody debris, is an important process impeding macroinvertebrate colonization. Our study highlights the importance of woody debris as habitat for aquatic communities and as a structural component of streams, with important implications for conservation and biomonitoring. We suggest that wood specialists could be a potential group for use in biomonitoring programs aimed at assessing the impact of deforestation.