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1.
《Limnologica》2021
Studies investigating the effects of human activities on the functional organization of macroinvertebrate communities in tropical streams and rivers are very limited, despite these areas witnessing the greatest loss of natural forests globally. We investigated changes in taxon richness, numerical abundance and biomass of macroinvertebrate functional feeding groups (FFGs) in streams draining different land-use types in the Sosiani-Kipkaren River in western Kenya. Twenty-one sites in river reaches categorized as forested, mixed, urban or agricultural were sampled during the dry and wet seasons. Collected macroinvertebrates were identified to the lowest taxon possible (mainly genus) and classified into five major FFGs; collector-gatherers, collector-filterers, scrapers, predators and shredders. There were significant (p < 0.05) spatial variation in habitat quality, organic matter standing stocks, total suspended solids, electrical conductivity, dissolved oxygen, temperature and nutrient concentrations across land-uses, with forested sites recording lowest values in mean water temperature, electrical conductivity and nutrients while recording highest levels in dissolved oxygen concentrations. Responses in macroinvertebrates to changes in land-use varied with richness, abundance and biomass showing differences within FFGs. Biomass-based metrics responded more strongly to change in land-use while taxon richness was the least predictive, indicating replacement of taxa within FFGs across land-use types. Higher shredder abundance, biomass and richness were recorded in forested streams which were cooler with protected riparian areas and high biomass of coarse particulate organic matter. Collector-gatherers dominated agricultural and urban streams owing to an abundance of particulate organic matter and nutrients, while scrapers responded positively to increased nutrient levels and open canopy in mixed and agricultural streams where primary production and algal biomass was likely increased. Overall, this study provides further evidence of the effects of agricultural and urban land-uses on tropical streams and rivers and contributes to the use of macroinvertebrate FFGs as indicators of ecological health. 相似文献
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《Limnologica》2017
Riparian vegetation is an important determinant of the physical, chemical, and biological condition of streams, and odonates are useful indicators of riparian condition. To identify environmental factors that structure Odonata assemblages in tropical forest streams, we collected adult odonate specimens and habitat data from 50 stream sites located in the Brazilian municipality of Paragominas (Pará state). We collected 1769 specimens representing 11 families, 41 genera, and 97 species. Of these species, 56 were Zygoptera, and 41 were Anisoptera. Improved environmental condition was reflected in increased Zygoptera species richness and reduced Anisoptera species richness. Channel shading was strongly and positively related to Zygoptera richness, and negatively to Anisoptera richness. Zygoptera species richness, but not Anisoptera species richness, was related positively to bank angle, quantity of wood in the stream bed, electrical conductivity, and decreased water temperature. Altered riparian vegetation structure was the principal determinant of odonate assemblage structure. Our results indicate that maintaining intact riparian vegetation is fundamental for conserving or re-establishing aquatic odonate assemblage structure. 相似文献
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Despite the known importance of water temperature for river ecosystems, the thermal regime of streams and rivers can be heavily modified by afforestation. Although the nature of the heat budget affecting streams in forested catchments shows high variability in space and time, most of the studies of stream temperature response to afforestation have lacked replication among streams. This study examined the impacts of coniferous forest plantations on stream water temperature at six sites (three forested and three open moorland) in the Yorkshire Dales, northern England. Our aim was to test the hypothesis that afforestation would alter the thermal regime of streams, leading to reduced year‐round thermal variability, and cooler summer/warmer winter water temperatures, relative to streams flowing across open moorland. Data collected from April 2007 to March 2009 showed similar thermal dynamics among all six streams over the study period, although variability in forested streams was markedly lower as expected. Mean and maximum daily water temperatures were significantly higher in open moorland streams for much of the year but while some forested streams were warmer than individual moorland streams during winter months (November to February), there was considerable overlap in water temperature between moorland and forest streams. Most stream temperature records showed evidence of low/no winter flow and freezing. These results contrast with many previous studies that have reported warmer temperatures in forested versus open moorland streams during winter, a finding that most likely reflects site‐specific hydrological, geomorphological and climatological influences on water temperature in addition to afforestation. This study demonstrates the need for replication of hydrological monitoring when examining the effects of basin‐scale management practices and provides further evidence for changes in stream thermal regime following afforestation, a practice that is likely to increase in future due to growing demands for increased forest cover in the UK uplands. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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《Limnologica》2015
Lotic ecosystems are highly affected by land use changes such as afforestation of natural areas for management or commercial purposes. The aim of this study was to analyze the effect of pine plantations on benthic invertebrate communities in mountain grassland streams. Additionally, we assessed if the hydrological period modifies the effect of afforestation on stream invertebrates. Three headwater streams draining grasslands (reference streams) and three draining plantations of Pinus elliottii were selected in a mountain watershed of Córdoba province (Argentina). Hydrologic and physicochemical variables were registered and benthic invertebrate samples were collected in each stream at two different hydrological periods. Total invertebrate abundance, richness and diversity were reduced in afforested streams as well as the number of indicator taxa. In addition, invertebrate functional structure (i.e. taxonomic richness and total and relative abundance of functional feeding groups, FFG) showed differences between streams with different riparian vegetation and between hydrological periods. Total abundance of all FFGs was lower in afforested streams and scrapers’ relative abundance was higher in grassland streams at the low water period. In addition, in most FFGs richness was diminished in afforested streams. Changes in light intensity, hydrology and coarse organic matter inputs produced by afforestation alter fluvial habitats and consequently the composition and trophic structure of invertebrate communities in grassland streams of Córdoba mountains. 相似文献
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《Limnologica》2020
We assessed water quality using physical, chemical, and biological characteristics in 37 streams between Puerto Maldonado and Cusco in Peru. Study sites ranged from ∼200 to 4000 m in elevation, with streams selected as pairs (control/natural vs. human impacted) along this gradient. In general, temperature decreased (R2 = 0.82) and other parameters increased [dissolved oxygen (R2 = 0.19), conductivity (R2 = 0.17), pH (R2 = 0.37)] with elevation. Macroinvertebrates were hand collected by professional entomologists and using leaf packs implemented by conservation workers. The professionals identified 213 unique taxa from the hand collections, with 80 species collected only one time. Data from control streams showed that as elevation increased, total richness (p = 0.008) and EPT richness (p = 0.050) decreased whereas Diptera richness increased (p = 0.002). NMS ordination indicated significant differences in macroinvertebrate assemblages when control streams from low and high elevations were contrasted. Hand collections also revealed significant differences between control and impact streams for total richness, EPT richness and % Diptera, but not for % EPT, % EPT richness, or % Diptera richness. The majority of the deployed leaf packs were successfully retrieved and contained many macroinvertebrates (Avg. = 141 individuals per pack). There were 98 unique taxa (family level or higher) identified from the leaf packs by the trained conservation workers. Fourteen of 15 macroinvertebrate community metrics (at the family level) were able to detect significant differences between control and impact sites. All of the family level metrics responded similarly across the elevation gradient except total richness, EPT richness, EPT count, and % Hydropsychids. Both the Costa Rica and the Virginia Save Our Stream Indexes were able to differentiate control from impacted streams using leaf pack data. Although the diversity of macroinvertebrates was higher for hand collections relative to leaf packs (due to greater habitats sampled and higher taxonomic resolution), leaf pack samples were better able to distinguish control from impacted streams. Specifically, leaf packs were able to discern impacts in streams at low elevation better than those at high elevation. Generally, macroinvertebrates indicated impact from urbanization to be worse than impacts from other human activities (i.e., gold mining and agriculture). Overall, hand collections will serve as an important reference of species diversity going forward while leaf packs processed by trained conservation workers are a viable method to monitor stream water quality in Peru and perhaps elsewhere. 相似文献
7.
《Limnologica》2014
Artificial drainage of forested wetlands to increase timber production has profoundly altered the hydrology of North-European landscapes during the 20th century. Nowadays, drainage ditches and small dredged streams can comprise most fluvial water bodies there, but the resulting ecological effects are poorly documented. In the current study, we explored, using fish as an indicator group, consequences of the transformation of natural stream networks to a mixture of natural and artificial watercourses. We asked whether the transformation results in impoverishment, enrichment or re-assembling of the communities both at watercourse and the landscape scales. We sampled fish in 98 sites in five well-forested regions in Estonia where ditches formed 83–92%, dredged streams 4–7%, and natural streams 3–10% of the total length of small watercourses. Based on a total of 6370 individual fish of 20 species, we found that, compared to natural streams, ditches had an impoverished fauna at both scales and both in terms of species richness and assemblage composition. Only natural streams hosted characteristic species (with Barbatula barbatula, Lampetra planeri and Lota lota emerging as significant indicators), while dredged streams had intermediate assemblages. The habitat factors explaining those drainage-related differences included a reduced flow velocity, loss of stream channel variability, less transparent water, and abundant aquatic vegetation. Hence, for stream-dwelling fish, drained forest landscapes represent degraded habitats rather than novel ecosystems, which contrasts with the transformation of terrestrial assemblages. Future studies should address whether that reflects the situation for whole aquatic assemblages, and how is the functioning of the hydrological systems affected. We suggest that the critical management issues for environmental mitigation of ditching effects on fish include basin scale spatial planning, protecting of the remaining natural streams, and rehabilitation of ditch channels in flat landscapes lacking beavers. 相似文献
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Dilce de Fátima Rossetti 《地球表面变化过程与地形》2010,35(10):1234-1239
Morphologies related to paleochannels are widespread through large areas of the Brazilian Amazonia. Despite the relevance for reconstructing the evolution of the largest fluvial system on Earth, detailed mapping of most of these features is still unavailable. The lack of works emphasizing Amazonian paleochannels represents an enormous bias toward the understanding of both migrating dynamics of Amazonian rivers through time and processes (e.g. tectonics, climate, sea‐level fluctuation) that might have promoted channel abandonment. A few previous studies have demonstrated the successful application of digital elevation model (DEM) collected during the Shuttle Radar Topography Mission (SRTM) for mapping morphologies related to paleochannels still preserved under forested lowland Amazonian areas. The present study applies different remote sensing techniques, including JERS‐1 90m, SAR/SIPAM‐6m, Landsat, and ASTER, to successfully unravel a myriad of paleochannels in Marajó Island (Amazon mouth), which were previously undetected using solely SRTM data. The results presented in this work are promising for mapping paleodrainage in other forested areas of the Amazonas basin. Considering the several problems involved on data acquisition aiming to approach the evolution of Amazonian rivers in space and time (e.g. large dimension, lack of natural geological exposures, difficult access, dense forest cover, and high cloud volume), a proper mapping of Amazonas paleodrainage using different remote sensing techniques is crucial to visualize potential paleochannel morphologies and patterns that are of high relevance for reconstructing the Amazonian fluvial dynamics through time. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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We examined the influence of algal farming on fish assemblages in two shallow coastal lagoons in Zanzibar, Tanzania. Fish assemblages were visually investigated using a belt transect method and the line-intercept technique was used to examine the substrate composition. 101 species of fish belonging to 31 families were recorded. Algal farming affected the associated fish fauna in terms of abundance, species richness, trophic identity and fish community composition. However, the impact differed between the lagoons. Algal farms in one lagoon hosted a more abundant and diversified fish fauna than controls, whereas farms in the other lagoon exhibited lower fish densities and similar species diversity compared to controls. The discrepancies between lagoons may be an effect of differences in farming intensity and character of the substratum. 相似文献
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《Limnologica》2017
We sampled different substrates (sand, gravel, leaf litter and stones) in the rainy and dry season to study the distribution and composition of benthic macroinvertebrates in tropical streams (northeastern Brazil). Benthic macroinvertebrates were distributed according to the substrates, with stones showing a higher richness and abundance of species and abundance of collector-gatherers and filter-collectors. The results of the PCoA showed a separation of stones from the other substrates and similarities between sand and gravel. 相似文献
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《Limnologica》2014
Drastic changes in the composition and physiognomy of riparian vegetation, such as the conversion of grassland to forest, are expected to alter interactions among light availability, primary producers and herbivores. Our aim was to examine in laboratory the influence of a ubiquitous grazer on periphyton grown in a grassland unshaded stream (reference) vs. periphyton from a nearby pine afforested stream. Besides, we evaluated how the community responds to the removal of grazing. Given that grassland streams are exposed to higher light intensity and grazers are more abundant compared to afforested streams, we proposed that if biofilm grown in the afforested stream are dominated by grazing-vulnerable algal species, grazing pressure by Helicopsyche sp. should be stronger. In addition, if biofilm from the afforested stream has low quality or is less abundant as food for consumers, the effects of Helicopsyche sp. may be stronger or weaker depending on their feeding decisions. Helicopsyche sp. caused a decrease in richness and diversity in periphyton grown in the grassland stream and its net grazing effect on chlorophyll a (Chl a) was higher. Algal community composition from grassland stream was strongly changed after grazing, with a decrease in the proportion of overstory algae. In contrast, algal community structure of periphyton from the afforested stream was neither affected by grazing nor by grazing exclusion. Helicopsyche sp. produced significant changes in a short time in structural attributes of algal communities, mainly in periphyton from the grassland stream suggesting that herbivory, as a functional factor, is diminished following afforestation. 相似文献
12.
Romina E. Principe Graciela B. Raffaini Cristina M. Gualdoni Ana M. Oberto Maria C. Corigliano 《Limnologica》2007,37(4):323-336
Methods to assess the physical habitat provide important tools for many aspects of river management. Hydraulic units (defined as a homogeneous patch of flow type and substrate) were described in mountain streams of Central Argentina and the distribution of macrozoobenthos in these habitat units was analyzed. Four streams from the upper Carcarañá River Basin (Córdoba, Argentina) were sampled in two hydrological periods. Hydraulic units (as substrate and flow type), current velocity, depth, macrophytes and macroalgae were assessed. Three benthic samples were taken in each hydraulic unit. A total of 12 hydraulic units were registered, which varied seasonally in their proportional abundance. The highest values of taxonomic richness, total abundance, diversity and evenness were found in the low-water period. The most heterogeneous hydraulic units (characterized by substrate of diverse grain size) presented the highest richness, diversity and evenness, whereas the highest total abundance was observed in hydraulic units with homogeneous substrate, such as bedrock or gravel sand. Canonical correspondence analysis grouped samples and taxa mainly in relation to the hydraulic units, and temporal variation in macroinvertebrate assemblages was observed. We found that the interaction between hydrological and geomorphological conditions affected benthic assemblages and that their organization is important at a mesoscale. Therefore, hydraulic units may be considered important tools in assessing stream integrity in lotic systems of central Argentina. 相似文献
13.
How much stream temperatures increase within riparian canopy openings and whether stream temperatures cool downstream of these openings both have important policy implications. Past studies of stream cooling downstream of riparian openings have found mixed results including rapid, slow, and no cooling. We collected longitudinal profiles of stream temperatures above, within, and below riparian forest openings along stream segments within otherwise forested riparian conditions to evaluate how sensitivity of stream temperatures to riparian conditions varied across landscape factors. We conducted these temperature surveys across openings in 12 wadeable streams within and near the Upper Little Tennessee River Basin in western North Carolina and northeastern Georgia. Basin areas ranged from 74 to 6,913 ha, and bankfull channel widths varied from 3.4 to 16.4 m. Stream temperatures were collected every 15 min using HOBO® data loggers for 2 weeks in each stream, repeated later in summer in some streams. Reference temperatures were highest in stream reaches at low elevations and with large drainage areas. Stream temperature increases in the middle of riparian gaps were highest when streams drained small high-elevation watersheds, and increases at the end of openings were highest when the opening length was large relative to watershed size. Downstream from openings, cooling rates were greatest in small, high-elevation headwater streams and also increased with larger increases in canopy cover. Stream segments that warmed the most within openings also featured higher cooling rates downstream. The data show that stream temperature sensitivity to canopy change is highly dependent on network position and watershed size. A better understanding of stream temperature responses to riparian vegetation may be useful to land managers and landowners prioritizing riparian forest restoration. 相似文献
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Historical land use as a driver of alternative states for stream form and function in forested mountain watersheds of the Southern Rocky Mountains 
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下载免费PDF全文 We demonstrate how land use can drive mountain streams in the Southern Rockies across a threshold to induce an alternative state of significantly reduced physical complexity of form and reduced ecological function. We evaluate field data from 28 stream reaches in relatively laterally unconfined valleys and unmanaged forest that is either old‐growth forest or naturally disturbed younger forest, and 19 stream reaches in managed forest with past land use. We evaluate potential differences in stream form, as reflected in channel planform, cross‐sectional geometry, and in‐stream wood loads, and stream function, as reflected in pool volume and storage of organic carbon. Field data indicate a threshold of differences in stream form and function between unmanaged and managed stream reaches, regardless of forest stand age, supporting our hypothesis that the legacy effects of past land use result in an alternative state of streams. Because physical complexity that increases stream retentiveness and habitat can maintain aquatic‐riparian ecosystem functions, the alternative physical state of streams in managed watersheds creates a physical template for an alternative ecological state with reduced pool volume, organic carbon storage, and ecosystem productivity. We recommend maintaining riparian forests that can supply large wood to streams as a stream restoration technique in historically forested stream segments. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Coarse particulate organic matter (CPOM, i.e. particles such as leaves, wood fragments, twigs, branches, flowers, seeds and fruits) in aquatic systems influences the flow, provides an important food source, and at the catchment scale, may significantly contribute to total carbon export. CPOM exports have rarely been quantified in subtropical, broadleaf forest streams. We captured CPOM in Bunte traps in the rainfall-dominated Vuelta de Zorra stream in southern Chile to (a) propose a novel classification to characterize the different CPOM components, (b) analyze the frequency of each matter class (i.e. leaves, wood fragments, and ‘others’) and its seasonal variability, (c) quantify the CPOM transported, (d) derive a model to quantify CPOM transport rates, and (e) compare the transported CPOM data with those from a unique long-term (> seven years) large wood monitoring dataset. Results showed that leaves were significantly more abundant than other types of CPOM in all seasons. The dry CPOM transport rate ranged over three orders of magnitude, and there was a significant relationship with mean discharge. Mean dry CPOM yield for the study period 2015–2017 was 4.6 kg/ha/yr when normalizing to the total forested catchment area. The 2009–2018 decadal average yield was 6.8 kg/ha/yr when normalizing to the total forested catchment area. These values are similar to measurements from deciduous and coniferous forests in streams in the United States and the Brazilian Mato Grosso and ~1/10 of the yields obtained in a Swiss torrent. Over a three-year period, the CPOM exports in Vuelta de Zorra ranged between 13 and 36% of the exported large wood (particles with diameters ≥ 100 mm and length ≥ 1 m) exports. Our data collected from an underrepresented area improve the understanding of global carbon budgets and cycling. © 2020 John Wiley & Sons, Ltd. 相似文献
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Urška Kuhar Tatjana Gregorc Miran Ren?elj Nina Šraj-Kr?i? Alenka Gaberš?ik 《Limnologica》2007,37(2):146-154
The distribution and abundance of macrophytes, land-use beyond the riparian zone, characteristics of the riparian zone and selected channel properties have been studied in 9 streams flowing through an agricultural landscape in the north-eastern part of Slovenia. The streams studied supported a rich macrophyte community. Altogether, 53 plant taxa were observed on 93 km of the streams. Canonical correspondence analysis indicated that 10 out of the 11 parameters examined significantly influenced macrophyte distribution. Of these, substrate characteristics and riparian vegetation type were the most influential. Species composition analysis revealed that the majority of species indicated moderate nutrient load while, in the more strongly modified reaches, species indicating eutrophic conditions, i.e. Myriophyllum spicatum and different species of genus Potamogeton, were more abundant. 相似文献
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Kaizhi LiJianqiang Yin Liangmin HuangJianlin Zhang Shumin LianCuimei Liu 《Continental Shelf Research》2011,31(9):979-989
The distribution and abundance of thaliaceans were studied in relation to physical and biological variables during summer and winter in the northwest continental shelf of South China Sea. Based on the topography and water mass of the surveyed region, it was divided into three subregions: region I (onshore waters of the east Leizhou Peninsula), region II (onshore waters of the east and southeast Hainan Island) and region III (offshore waters from Leizhou Peninsula to Hainan Island). During summer due to a strong southwest monsoon, a cold eddy and coastal upwelling dominated in regions I and II, respectively, whereas the onshore and offshore waters were vertically mixed during winter due to a strong northeast monsoon. A total of 18 thaliacean species (including 3 subspecies) were collected. The mean species richness was higher in summer compared to winter, with the occurrence of higher values during summer and winter at region II and region III, respectively. The average thaliacean abundance is also higher in summer than in winter, with higher values at region I in summer and no significant difference among three subregions in winter. Doliolum denticulatum and Thalia democratica were the dominant species during summer and winter. The results suggested that the seasonal and spatial distribution of thaliacean richness was considered to be the result of physical factors such as temperature and ocean current in summer and winter. Spatial distribution of thaliacean abundance was affected by chlorophyll a concentration increased by the occurrence of coastal upwelling and cold eddy in summer. Southwest and northeast monsoons are shown to play an important role in shaping the distribution of species richness and abundance of thaliaceans in the northwest continental shelf of South China Sea. 相似文献
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《Limnologica》2020
In recent decades, riparian vegetation has been removed from important ecosystems around the world, in spite of its high ecological importance for aquatic biota. Nevertheless, the effects of catchment land use on zooplankton have been little studied. The present study investigated if replanting riparian vegetation in a tropical reservoir influences the richness and abundance of cladoceran communities, by addressing the question of whether cladocerans show differences in richness and abundance among four levels of riparian vegetation conditions: 1) native forest (NF); 2) 30 years after forest replanting (R1); 3) 10 years after forest replanting (R2); and 4) no forest (No-F). Zooplankton samples were obtained from 9 stations in the Volta Grande Reservoir, Minas Gerais, Brazil. Cladocerans in zones NF and R1 showed higher levels of richness and abundance than in zones No-F and R2. Ceriodaphnia reticulata, Ceriodaphnia laticaudata, and Diaphanosoma spinulosum showed higher abundances in zones NF and R1. Cladoceran community structure was influenced by the different levels of riparian vegetation. This study showed that the presence and age of riparian forest positively influence the abundance, richness and diversity of cladoceran assemblages. Furthermore, our results indicated that C. reticulata, C. laticaudata and D. spinulosum are more efficient than other cladocerans in exploiting allochthonous resources provided by riparian forest. Functional diversity was higher in zones NF and R1, suggesting that the trait composition of cladoceran assemblages responds positively to recovery of riparian forest. Overall, our research suggests that cladocerans are good indicators of riparian vegetation conditions and that restoration of riparian forest positively affects cladoceran assemblages of tropical reservoirs. 相似文献