Gradient Of Agricultural Land Use Research Articles

Ecological traits interact with landscape context to determine bees’ pesticide risk

Widespread contamination of ecosystems with pesticides threatens non-target organisms. However, the extent to which life-history traits affect pesticide exposure and resulting risk in different landscape contexts remains poorly understood. We address this for bees across an agricultural land-use gradient based on pesticide assays of pollen and nectar collected by Apis mellifera, Bombus terrestris and Osmia bicornis, representing extensive, intermediate and limited foraging traits. We found that extensive foragers (A. mellifera) experienced the highest pesticide risk—additive toxicity-weighted concentrations. However, only intermediate (B. terrestris) and limited foragers (O. bicornis) responded to landscape context—experiencing lower pesticide risk with less agricultural land. Pesticide risk correlated among bee species and between food sources and was greatest in A. mellifera-collected pollen—useful information for future postapproval pesticide monitoring. We provide foraging trait- and landscape-dependent information on the occurrence, concentration and identity of pesticides that bees encounter to estimate pesticide risk, which is necessary for more realistic risk assessment and essential information for tracking policy goals to reduce pesticide risk.

Honey bee-collected pollen richness and protein content across an agricultural land-use gradient

Higher protein content and greater taxonomic richness of pollen have been noted as beneficial for bee health, but the relationship between pollen protein content and richness as well as how pollen protein content varies across landscape gradients remain understudied. We assessed correlations between pollen protein content and plant species richness and species composition in pollen collected from honey bee colonies across three states over 2 years. We selected sites along an agricultural-grassland gradient to investigate how pollen protein content and species composition varied with land-use. We observed a weak, negative relationship between pollen protein content and taxonomic richness, although we found no evidence of relationships between land-use and either pollen richness or species composition. Results suggest that the richness of pollen collected by honey bees can, albeit weakly, correlate with the pollen protein content in agroecosystems of the Upper Midwest, and that in some systems, land use may have minimal influence on the species collected by honey bees.

Agricultural land use changes stream dissolved organic matter via altering soil inputs to streams

Agricultural land use leads to significant changes in both the quality (e.g., sources and compositions) and quantity of dissolved organic matter (DOM) exported from terrestrial to aquatic ecosystems. However, the effect of agricultural activities often interacts with those of hydroclimatic drivers, making it difficult to delineate agriculture-induced changes and identify associated mechanisms. Using partial least square path modeling (PLS-PM), we examined the relative importance of agricultural land use, stream order, precipitation, and temperature in mediating allochthonous versus autochthonous sources and pathways that influenced stream DOM quality and quantity. We analyzed stream water DOM from 15 small streams draining watersheds across a gradient of agricultural land use in Southeast USA for about one year. For DOM quantity, agricultural land use increased the export of DOC and various DOM pools (terrestrial humic, microbial humic, and protein-like DOM) from land to streams, and for DOM quality, agricultural streams showed greater proportions of microbial humic compounds than forested streams. The PLS-PM model for DOM quantity accounted for 75.5% of total variance and identified that agricultural land use increased stream water DOM quantity primarily through increasing allochthonous inputs, which can be attributed to shallower flow paths in agricultural watersheds that enabled the export of organic materials from the upper, organic-rich soil horizon. PLS-PM models for DOM quality only explained ~13% of the total variance, highlighting the complex dynamics between environmental drivers and stream water DOM. Relative to commonly used multivariate statistic modeling (e.g., redundancy analysis (RDA)), PLS-PM models offer the advantages of identifying the primary pathway by which agricultural lands alter freshwater DOM and quantifying the relative importance of interactive effects of agriculture and hydroclimatic drivers. Therefore, structural equation modeling is a powerful tool that should be more widely adopted to distinguish among multiple drivers and mechanisms regulating freshwater biogeochemistry.

Do the Quality and Quantity of Honey Bee-Collected Pollen Vary Across an Agricultural Land-Use Gradient?

Pollen is the source of protein for most bee species, yet the quality and quantity of pollen is variable across landscapes and growing seasons. Understanding the role of landscapes in providing nutritious forage to bees is important for pollinator health, particularly in areas undergoing significant land-use change such as in the Northern Great Plains (NGP) region of the United States where grasslands are being converted to row crops. We investigated how the quality and quantity of pollen collected by honey bees (Apis mellifera L. [Hymenoptera: Apidae]) changed with land use and across the growing season by sampling bee-collected pollen from apiaries in North Dakota, South Dakota, and Minnesota, USA, throughout the flowering season in 2015-2016. We quantified protein content and quantity of pollen to investigate how they varied temporally and across a land-use gradient of grasslands to row crops. Neither pollen weight nor crude protein content varied linearly across the land-use gradient; however, there were significant interactions between land use and sampling date across the season, particularly in grasslands. Generally, pollen protein peaked mid-July while pollen weight had two maxima in late-June and late-August. Results suggest that while land use itself may not correlate with the quality or quantity of pollen resources collected by honey bees among our study apiaries, the nutritional landscape of the NGP is seasonally dynamic, especially in certain land covers, and may impose seasonal resource limitations for both managed and native bee species. Furthermore, results indicate periods of qualitative and quantitative pollen dearth may not coincide.

Nutritional status of honey bee (Apis mellifera L.) workers across an agricultural land-use gradient

Land use, habitat, and forage quality have emerged as critical factors influencing the health, productivity, and survival of honey bee colonies. However, characterization of the mechanistic relationship between differential land-use conditions and ultimate outcomes for honey bee colonies has been elusive. We assessed the physiological health of individual worker honey bees in colonies stationed across a gradient of agricultural land use to ask whether indicators of nutritional physiology including glycogen, total sugar, lipids, and protein were associated with land-use conditions over the growing season and colony population size the subsequent spring during almond pollination. Across the observed land-use gradient, we found that September lipid levels related to growing-season land use, with honey bees from apiaries surrounded by more favorable land covers such as grassland, pasture, conservation land, and fallow fields having greater lipid reserves. Further, we observed a significant relationship between total protein during September and population size of colonies during almond pollination the following February. We demonstrate and discuss the utility of quantifying nutritional biomarkers to infer land-use quality and predict colony population size.

Agricultural land use impacts microbial community structure of streambed sediments

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 83:225-236 (2019) - DOI: https://doi.org/10.3354/ame01905 Agricultural land use impacts microbial community structure of streambed sediments Caitlyn A. Griffith1, Peng Shang2, YueHan Lu2, Ethan J. Theuerkauf3, Antonio B. Rodriguez4, Robert H. Findlay1,* 1Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama 35401, USA 2Department of Geological Sciences, The University of Alabama, 201 7th Ave, Tuscaloosa, Alabama 35485, USA 3Illinois State Geological Survey, Prairie Research Institute, The University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, USA 4University of North Carolina, Institute of Marine Sciences, 3431 Arendell St, Morehead City, North Carolina 28557, USA *Corresponding author: rfindlay@ua.edu ABSTRACT: Agricultural land use is known to adversely affect freshwater ecosystems, and recent studies have shown that it can significantly alter dissolved organic matter (DOM) concentrations and quality. DOM quantity and quality are key determinants of microbial community structure in streams and have been linked to changes in community abundance and composition. Considering the vital ecological role sediment microbes play in stream ecosystems, it is important to understand how agricultural land use changes affect stream microbial community structure. This study was conducted to determine if variation in sediment microbial biomass community structure could be attributed to differences in agricultural land use. Microbial biomass, microbial community structure, and stream water parameters were compared on 2 dates from 6 sites representing a gradient of agricultural land use from 18 to 64% within the Bear Creek Watershed in northwest Alabama, USA. Total microbial biomass, determined as phospholipid phosphate, was strongly influenced by sediment surface area and, to a lesser extent, correlated with sampling date and land use. Sediment microbial community structure, determined by phospholipid fatty acid analysis, was significantly correlated to percent agricultural land use in the watershed, as well as stream water DOM humification index, and sediment δ15N values and surface area. Microbial community structure also differed between sampling dates. These findings demonstrate that agricultural land use is linked via alteration of stream water and sediment organic matter to changes in sediment microbial structure which may, at least in part, account for widely observed changes in stream ecosystem functioning associated with agricultural activities. KEY WORDS: Microbial community structure · Streams · Agricultural land use · DOM Full text in pdf format Supplementary material PreviousNextCite this article as: Griffith CA, Shang P, Lu Y, Theuerkauf EJ, Rodriguez AB, Findlay RH (2019) Agricultural land use impacts microbial community structure of streambed sediments. Aquat Microb Ecol 83:225-236. https://doi.org/10.3354/ame01905 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in AME Vol. 83, No. 3. Online publication date: October 02, 2019 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2019 Inter-Research.

Climatic and watershed controls of dissolved organic matter variation in streams across a gradient of agricultural land use

Human land use has led to significant changes in the character of dissolved organic matter (DOM) in lotic ecosystems. These changes are expected to have important environmental and ecological consequences. However, high spatiotemporal variability has been reported in previous studies, and the underlying mechanisms remain inadequately understood. This study assessed variation in the properties of stream water DOM within watersheds across a gradient of agricultural land use with grazing pasture lands as the dominant agricultural type in the southeastern United States. We collected water samples under baseflow conditions five times over eight months from a regional group of first- to fourth-order streams. Samples were analyzed for dissolved organic carbon (DOC) concentration, DOM quality based on absorbance and fluorescence properties, as well as DOM biodegradability. We found that air temperature and antecedent hydrological conditions (indicated by antecedent precipitation index and stream water sodium concentrations) positively influenced stream water DOC concentration, DOM fluorescence index, and the proportion of soil-derived, microbial humic fluorescence. This observation suggests that elevated production and release of microbial DOM in soils facilitated by high temperature, in conjunction with strong soil-stream hydrological connectivity, were important drivers for changes in the concentration and composition of stream water DOM. By comparison, watersheds with a high percentage of agricultural land use showed higher DOC concentration, larger proportion of soil-derived, humic-like DOM compounds, and higher DOC biodegradability. These observations reflect preferential mobilization of humic DOM compounds from shallow organic matter-rich soils in agricultural watersheds, likely due to enhanced soil erosion, organic matter oxidation and relatively shallow soil-to-stream flow paths.

Effect of Native Vegetation Loss on Stream Ecosystem Processes: Dissolved Organic Matter Composition and Export in Agricultural Landscapes

Stream and river ecosystems are dependent on energetic inputs from their watersheds and thus shifts in land use from forest cover to agriculture will affect stream community composition and function. The disruption of forest-aquatic linkages alters the organic matter resources in agricultural streams. Dissolved organic matter (DOM) is the dominant form of organic matter in aquatic ecosystems, and a microbial energy source that is important for stream respiration. The concentrations and characteristics of DOM are regulated by both terrestrial (for example, terrestrial organic matter supply) and in-stream processes (for example, microbial respiration and periphyton production) that are influenced by land management. The effects of watershed land use and topographic, soil and climatic variables on DOM quantity (dissolved organic carbon concentration and load), source (terrestrial or in-stream) and quality (composition and lability) were measured in 14 streams across an agricultural land-use gradient. DOC concentration was positively correlated with watershed pasture cover and negatively correlated with watershed relief. No watershed variables were important correlates of DOC load. Stream DOM was primarily of terrestrial origin, but DOM in agricultural streams had a greater proportion of sources from in-stream sources. This may be due to reduced connection with riparian vegetation and increased in-stream primary production. We suggest that maintaining watershed tree cover greater than 52% and ensuring less than 10% of the length of riparian corridor is cleared for pasture could minimize changes to DOM composition. This is important to avoid flow-on effects for stream ecosystem processes that are mediated by DOM. Long-term DOM monitoring will be valuable for assessing the functional impacts of land-use change.

Nutrient recycling by fish in streams along a gradient of agricultural land use

Nutrient recycling is an essential ecosystem process provided by animals. In many aquatic systems, fish have been identified as important in ecosystem nutrient recycling; however, this importance can vary widely between systems. The factors controlling intersystem variation in animal-mediated nutrient cycling have rarely been examined and as such it remains unclear what impact human landscape changes will have upon these processes. Here we examined rates of nutrient recycling for temperate stream fish assemblages along a gradient of agricultural land use (proportion cropland in the watershed: 1–59%). We quantified nutrient excretion rates of both ammonium–N (NH4+–N) and phosphate (as soluble reactive phosphate: SRP) for fish assemblages at eight streams in southern Ontario, Canada with species-specific excretion measurements and quantitative assemblage sampling. For both nutrients, total assemblage excretion exhibited a strong positive relationship with riparian cropland. The distance required for fish assemblages to turn over ambient nutrient pools was shorter for cropland systems, indicating that the relative importance of excreted nutrients was higher in these systems. Based on measured uptake rates of NH4+–N in two streams (one higher cropland and one low cropland) and on modeled uptake rates for all streams, the proportion of ecosystem demand that can be satisfied by excretion is generally higher in the more agricultural streams. These patterns appear to be driven largely by disproportionate increases in fish assemblage biomass with increasing stream nutrient concentrations.

Shifts in allochthonous input and autochthonous production in streams along an agricultural land-use gradient

Relative contributions of allochthonous inputs and autochthonous production vary depending on terrestrial land use and biome. Terrestrially derived organic matter and in-stream primary production were measured in 12 headwater streams along an agricultural land-use gradient. Streams were examined to see how carbon (C) supply shifts from forested streams receiving primarily terrestrially derived C to agricultural streams, which may rely primarily on C derived from algal productivity. We measured allochthonous input, chlorophyll a concentration, and periphyton biomass in each stream, and whole-stream metabolism in six streams. Our results suggest a threshold between moderate- and heavy-agriculture land uses in which terrestrially derived C is replaced by in-stream algal productivity as the primary C source for aquatic consumers. A shift from allochthonous to autochthonous production was not evident in all heavy-agriculture streams, and only occurred in heavy-agriculture streams not impacted by livestock grazing. We then compared our findings to rates of allochthonous input and GPP in streams with minimal human influences in multiple biomes to assess how land-use practices influence C sources to stream ecosystems. The proportion of C derived from allochthonous versus autochthonous sources to heavy-agriculture streams was most similar to grassland and desert streams, while C sources to forested, light-, and moderate-agriculture streams were more similar to deciduous and montane coniferous forest streams. We show that C source to streams is dependent on land use, terrestrial biome, and degradation of in-stream conditions. Further, we suggest that within a biome there seems to be a compensation such that total C input is nearly equal whether it is from allochthonous or autochthonous sources.

Inadequacy of size distributions of stream benthic diatoms for environmental monitoring

Benthic diatom assemblages respond to changes in water quality, and this response is evidenced by shifts in taxonomic composition. As a result, several taxon-based indices have been developed for monitoring purposes. Some authors have suggested that diatom body size might provide a simpler method for bioassessment than taxonomy-based approaches. Moreover, current knowledge of algal ecology suggests that the slopes and intercepts of density size distributions should vary with environmental characteristics. However, results from studies of the relationship between algal size and trophic variables including P have been mixed. Our objectives were to examine normalized density size distributions and richness size distributions of benthic diatoms in streams along a gradient of agricultural land use to determine whether the size distributions changed in relation to environmental variables. Benthic diatoms from 29 streams in eastern Canada were identified and average body size measurements were obtained for each taxon. Normalized density size distributions and richness size distributions were plotted, and slopes and intercepts were compared among sites using general linear models (GLMs). Despite taxonomic differences in the assemblages, slopes of the normalized density size distributions did not differ among the 29 sites, and distribution shape and intercepts for the richness size distributions did not differ among sites. The intercepts of the normalized density size distributions were significantly different among sites, and this variation was attributed in part to the effect of several environmental variables including N and P. However, this difference in intercepts represented a change in density across all size classes, rather than a size-specific change. Environmental variables did not explain a significant amount of the variance in the shapes of density or richness size distributions. These results suggest that the slopes of lotic benthic diatom size distributions do not differ in response to environmental variables including P. Thus, benthic diatom body size should not be used as a proxy for nutrient status in environmental monitoring.

Effects of agricultural land use on the composition of fluvial dissolved organic matter

Nearly 40% of the Earth’s ice-free surface area is cropland or pasture. Measurements of dissolved organic matter along a gradient of agricultural land use suggest that agricultural watersheds contain less complex, more microbially derived dissolved organic matter than natural wetlands. Nearly 40% of the Earth’s ice-free surface area is cropland or pasture1. Agricultural land use can increase the delivery of nutrients such as nitrogen and phosphorus to fluvial ecosystems2, but the impact of farming on riverine dissolved organic carbon is still largely unknown, despite increasing recognition that rivers act as important modifiers in the global carbon cycle3,4. Here, we examine the character of riverine dissolved organic matter in 34 watersheds along a gradient of agricultural land use. We show that changes in the character of dissolved organic matter are related to agricultural land use, nitrogen loading and wetland loss. Specifically, we find that the structural complexity of dissolved organic matter decreases as the ratio of continuous croplands to wetlands increases. At the same time, the amount of microbially derived dissolved organic matter increases with greater agricultural land use. Furthermore, we find that periods of soil dryness are associated with a decrease in the structural complexity of dissolved organic matter. We suggest that these effects of land use and climate on the character of riverine dissolved organic matter have important implications for global carbon cycling, owing to their potential to control rates of microbial carbon processing (for example, uptake, retention and outgassing) in agricultural systems.

Are leaf breakdown rates a useful measure of stream integrity along an agricultural landuse gradient?

Biological indicators often are used to assess and manage water quality in anthropogenically altered stream systems. Leaf breakdown has the potential to be a good indicator of stream integrity because it integrates a variety of biological, chemical, and physical conditions. Red maple (Acer rubrum L.) leaf breakdown rates were measured along a gradient of agricultural land use in southern Appalachian streams to assess the use of leaf breakdown rates as a measure of stream integrity. Landuse categories included forested, light agriculture, moderate agriculture, and heavy agriculture. Leaf breakdown rates were related to landuse category but did not differ significantly among landuse categories. Nutrient concentration, temperature, and sedimentation increased, and dissolved O2 decreased along the landuse gradient from forest to heavy agriculture. Macroinvertebrate richness, macroinvertebrate density, and shredder density were the only significant predictors of leaf breakdown rates. We conclude that leaf breakdown rates may not be a useful indicator of stream integrity because of the confounding effects that agricultural land use has on breakdown rates.

Response of Stream Macroinvertebrates to Agricultural Land Cover in a Small Watershed

ABSTRACT We conducted a three-year study of the aquatic macroinvertebrate community of a rural, central-Pennsylvania, upland watershed (7.3 km2) with subwatersheds affected by a gradient of agricultural land use (87% forest to 96% managed agriculture). Macroinvertebrate samples were collected at 16 sites on first- to third-order streams within the watershed in May or June. Nitrate concentrations and habitat quality were also determined at these sites. The taxonomic richness of sensitive macroinvertebrates (mayflies and caddisflies) was lower in streams draining subwatersheds with high percentage agricultural land cover compared to low. Habitat quality decreased as percentage agricultural land cover increased. Nitrate concentration increased with percentage agricultural land cover for the three years of study but was only correlated with habitat quality in one year. Our data suggest that a high percentage of agricultural land cover reduced the number of sensitive macroinvertebrate taxa and produced a macroinvertebrate community composition that reflected altered stream habitat.

Responses of Physical, Chemical, and Biological Indicators of Water Quality to a Gradient of Agricultural Land Use in the Yakima River Basin, Washington

The condition of 25 stream sites in the Yakima River Basin, Washington, were assessed by the U.S. Geological Survey's National Water-Quality Assessment Program. Multimetric condition indices were developed and used to rank sites on the basis of physical, chemical, and biological characteristics. These indices showed that sites in the Cascades and Eastern Cascades ecoregions were largely unimpaired. In contrast, all but two sites in the Columbia Basin ecoregion were impaired, some severely. Agriculture (nutrients and pesticides) was the primary factor associated with impairment and all impaired sites were characterized by multiple indicators of impairment. All indices of biological condition (fish, invertebrates, and algae) declined as agricultural intensity increased. The response exhibited by invertebrates and algae suggested a threshold response with conditions declining precipitously at relatively low levels of agricultural intensity and little response at moderate to high levels of agricultural intensity. This pattern of response suggests that the success of mitigation will vary depending upon where on the response curve the mitigation is undertaken. Because the form of the community condition response is critical to effective water-quality management, the National Water-Quality Assessment Program is conducting studies to examine the response of biota to gradients of land-use intensity and the relevance of these responses to water-quality management. These land-use gradient pilot studies will be conducted in several urban areas starting in 1999.

Organic Matter Dynamics in the Kuparuk River, a Tundra River in Alaska, USA

Previous articleNext article No AccessStream Organic Matter BudgetsOrganic Matter Dynamics in the Kuparuk River, a Tundra River in Alaska, USAChris J. Harvey, Bruce J. Peterson, W. Breck Bowden, Linda A. Deegan, Jacques C. Finlay, Anne E. Hershey, and Michael C. MillerChris J. Harvey Search for more articles by this author , Bruce J. Peterson Search for more articles by this author , W. Breck Bowden Search for more articles by this author , Linda A. Deegan Search for more articles by this author , Jacques C. Finlay Search for more articles by this author , Anne E. Hershey Search for more articles by this author , and Michael C. Miller Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 16, Number 1Mar., 1997 Article DOIhttps://doi.org/10.2307/1468225 Views: 9Total views on this site Citations: 15Citations are reported from Crossref Journal History This article was published in the Journal of the North American Benthological Society (1986-2011), which is continued by Freshwater Science (2012-present). Copyright 1997 The North American Benthological SocietyPDF download Crossref reports the following articles citing this article:J. David Allan, Maria M. Castillo, Krista A. Capps Carbon Dynamics and Stream Ecosystem Metabolism, (Mar 2021): 421–452.https://doi.org/10.1007/978-3-030-61286-3_14Arturo Elosegi, Jesús Pozo Litter Input, (Jul 2020): 3–12.https://doi.org/10.1007/978-3-030-30515-4_1Christopher T. Robinson, Andre R. Siebers, and Johannes Ortlepp Long-term ecological responses of the River Spöl to experimental floods, Freshwater Science 37, no.33 (Jul 2018): 433–447.https://doi.org/10.1086/699481James Wood, Meryom Pattillo, Mary Freeman Organic-Matter Retention and Macroinvertebrate Utilization of Seasonally Inundated Bryophytes in a Mid-Order Piedmont River, Southeastern Naturalist 15, no.33 (Sep 2016): 403–414.https://doi.org/10.1656/058.015.0303Amy Townsend-Small, James W. McClelland, R. Max Holmes, Bruce J. Peterson Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic, Biogeochemistry 103, no.1-31-3 (May 2010): 109–124.https://doi.org/10.1007/s10533-010-9451-4Elizabeth M. Hagen, Matthew E. McTammany, Jackson R. Webster, Ernest F. Benfield Shifts in allochthonous input and autochthonous production in streams along an agricultural land-use gradient, Hydrobiologia 655, no.11 (Aug 2010): 61–77.https://doi.org/10.1007/s10750-010-0404-7W. B. Bowden, M. N. Gooseff, A. Balser, A. Green, B. J. Peterson, J. Bradford Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems, Journal of Geophysical Research: Biogeosciences 113, no.G2G2 (Jun 2008): n/a–n/a.https://doi.org/10.1029/2007JG000470J. W. McClelland, M. Stieglitz, Feifei Pan, R. M. Holmes, B. J. Peterson Recent changes in nitrate and dissolved organic carbon export from the upper Kuparuk River, North Slope, Alaska, Journal of Geophysical Research: Biogeosciences 112, no.G4G4 (Nov 2007): n/a–n/a.https://doi.org/10.1029/2006JG000371K. Slavik, B. J. Peterson, L. A. Deegan, W. B. Bowden, A. E. Hershey, J. E. Hobbie LONG-TERM RESPONSES OF THE KUPARUK RIVER ECOSYSTEM TO PHOSPHORUS FERTILIZATION, Ecology 85, no.44 (Apr 2004): 939–954.https://doi.org/10.1890/02-4039U. Uehlinger, R. Zah Organic Matter Dynamics, (Jan 2003): 199–215.https://doi.org/10.1007/978-94-017-0181-5_12James H. Thorp, Michael D. Delong Dominance of autochthonous autotrophic carbon in food webs of heterotrophic rivers, Oikos 96, no.33 (Jun 2002): 543–550.https://doi.org/10.1034/j.1600-0706.2002.960315.xJames O. Lee and Anne E. Hershey1 Effects of aquatic bryophytes and long-term fertilization on arctic stream insects, Journal of the North American Benthological Society 19, no.44 (Jul 2015): 697–708.https://doi.org/10.2307/1468127 Patrick J. Mulholland Dissolved Organic Matter Concentration and Flux in Streams, Journal of the North American Benthological Society 16, no.11 (Nov 2015): 131–141.https://doi.org/10.2307/1468246 J. R. Webster , and Judy L. Meyer Organic Matter Budgets for Streams: A Synthesis, Journal of the North American Benthological Society 16, no.11 (Nov 2015): 141–161.https://doi.org/10.2307/1468247Arturo Elosegi, Jesús Pozo Litter Input, (): 3–11.https://doi.org/10.1007/1-4020-3466-0_1

Large-Scale Trends for Stream Benthic Respiration

Large-Scale Trends for Stream Benthic Respiration

Stream Organic Matter Inputs, Storage, and Export for Satellite Branch at Coweeta Hydrologic Laboratory, North Carolina, USA

Stream Organic Matter Inputs, Storage, and Export for Satellite Branch at Coweeta Hydrologic Laboratory, North Carolina, USA

Canada Stream: A Glacial Meltwater Stream in Taylor Valley, South Victoria Land, Antarctica

The McMurdo Dry Valleys of South Victoria Land, Antarctica, form the largest of the desert oases found along the coast of Antarctica. Although this region is an extreme cold desert, glacial meltwater streams, which flow for 6-10 wk during the austral summer, are a prominent feature of the landscape. Canada Stream is in Taylor Valley and is one of 3 major streams draining Canada Glacier. The surrounding landscape is characterized by an absence of plant life, an underlying permafrost at a depth of 0.5 m, and prominent "patterned ground" features, which are large (3-5 m across) polygonal patterns formed through freeze/thaw cycles. In contrast to the barren landscape, many of the streams contain perennial algal mats and mosses, illustrating that the presence of liquid water allows for a photosynthetically based ecosystem even under the harshest conditions. Canada Stream is one of 10 streams that flow into Lake

Long-term effects of inundation dynamics and agricultural land-use on the distribution of soil macrofauna in fluvisols

The distribution of soil macrofauna was studied in fluvisols. Ordination procedures were used to investigate changes in pppulation structure, long-term effects of agriculture, and inundation dynamics. The main environmental factor in the decrease in species numbers, abundances, and fresh biomass of isopods and diplopods in intensively farmed sites was the gradient of agricultural land-use. The land-use gradient also influenced the earthworm community by increasing the fresh biomass and the mean individual weight of adults. The long-term effects of inundations on the soil macrofauna distribution showed that several species preferred periodically or episodically flooded locations.