Preliminary characterization and source assessment of PAHs in tributary sediments of the Athabasca River,Canada

The Athabasca Oil Sands are one of four natural oil sands deposits in Northern Alberta, Canada. As a number of new mines are planned in the area, there is a need to establish background levels of natural hydrocarbon release prior to these developments. To this end, various environmental samples were taken from selected tributaries in the oil sands region of the Athabasca River Basin and analysed by gas chromatography/mass spectrometry (GC/MS) for polycyclic aromatic hydrocarbons (PAHs) and their alkylated analogues. Samples were collected over 3 years (1998-2000) to provide an increased understanding of the spatial distribution, nature and extent of natural hydrocarbon release to the environment. Results indicated that levels of total PAHs were elevated in the tributaries (up to 34.7 µg/g) compared to the main stem Athabasca River (<2 µg/g). As expected, samples from the oil sands deposits contained the greatest amounts of PAHs and alkylated PAHs. Profiles of the alkylated PAM distributions were very similar, indicating that all the samples tested were from a common petrogenic source.     

Using Topography to Meet Wildlife and Fuels Treatment Objectives in Fire-Suppressed Landscapes

Past forest management practices, fire suppression, and climate change are increasing the need to actively manage California Sierra Nevada forests for multiple environmental amenities. Here we present a relatively low-cost, repeatable method for spatially parsing the landscape to help the U.S. Forest Service manage for different forest and fuel conditions to meet multiple goals relating to sensitive species, fuels reduction, forest products, water, carbon storage, and ecosystem restoration. Using the Kings River area of the Sierra Nevada as a case study, we create areas of topographically-based units, Landscape Management Units (LMUs) using a three by three matrix (canyon, mid-slope, ridge-top and northerly, southerly, and neutral aspects). We describe their size, elevation, slope, aspect, and their difference in inherent wetness and solar radiation. We assess the predictive value and field applicability of LMUs by using existing data on stand conditions and two sensitive wildlife species. Stand conditions varied significantly between LMUs, with canyons consistently having the greatest stem and snag densities. Pacific fisher (Martes pennanti) activity points (from radio telemetry) and California spotted owl (Strix occidentalis occidentalis) nests, roosts, and sightings were both significantly different from uniform, with a disproportionate number of observations in canyons, and fewer than expected on ridge-tops. Given the distinct characteristics of the LMUs, these units provide a relatively simple but ecologically meaningful template for managers to spatially allocate forest treatments, thereby meeting multiple National Forest objectives. These LMUs provide a framework that can potentially be applied to other fire-dependent western forests with steep topographic relief.     

The benefits of Q + PPGIS for coupled human-natural systems research: A systematic review

Managing complex problems in socio-ecological systems (SES) requires innovative approaches, which account for multiple scales, large datasets, and diverse lived experiences. By combining two commonly utilized mixed-methods, public participation GIS (PPGIS) and Q-method (Q), Q + PPGIS has the potential to reveal competing agendas and reduce conflict, but its benefits and weaknesses are comparatively understudied. Using a systematic review, we evaluated how different studies have employed and implemented the Q + PPGIS method. We found 16 studies, comprising 30 publications, with considerable variation in their geographic foci, research disciplines, and addressed SES challenges. These studies exhibit a lack of cohesion between methodological design and implementation and the absence of a consistent application of the method. Nonetheless, Q + PPGIS offers a tool that can guide policy, better inform stakeholders, and reduce conflict based on misconceptions. Resolving the shortcomings identified here will broaden Q + PPGIS utility in geographically situating and representing multiple realities within complex socio-ecological systems challenges.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-022-01709-z.     

Pre-instrumental perspectives on Arkansas River cross-watershed flow variability

We present four reconstruction estimates of Arkansas River baseflow and streamflow using a total of 78 tree-ring chronologies for three streamflow gages, geographically spanning the headwaters in Colorado to near the confluence of the Arkansas-Mississippi rivers. The estimates represent different seasonal windows, which are dictated by the shared limiting forcing of precipitation on seasonal tree growth and soil moisture—and subsequently on the variability of Arkansas River discharge. Flow extremes that were higher and lower than what has been observed in the instrumental era are recorded in each of the four reconstructions. Years of concurrent, cross-basin (all sites) low flow appear more frequently during the 20th and 21st Centuries compared to any period since 1600 A.D., however, no significant trend in cross-basin low flow is observed. As the most downstream major tributary of the Mississippi River, the Arkansas River directly influences flood risk in the Lower Mississippi River Valley. Estimates of extreme high flow in downstream reconstructions coincide with specific years of historic flooding documented in New Orleans, Louisiana, just upstream of the Mississippi River Delta. By deduction, Mississippi River flooding in years of low Arkansas River flow imply exceptional flooding contributions from the Upper Mississippi River catchments.     

Sequential element extraction of soils from abandoned farms: an investigation of the partitioning of anthropogenic element inputs from historic land use

Enhanced soil element concentrations may serve as indicators not only of modern pollution, but also of former historic and/or pre-historic human activity. However, there is little consensus over the most appropriate means of extraction for identifying chemical signatures of modern and archaeological pollution. This study addressed this question by using a 5-step sequential extraction to examine the partitioning of elements within the soil. Samples were taken from known functional areas (hearth, house, byre, arable, and grazing areas) on a 19th century abandoned croft (small farm). A hot nitric acid digest and five-stage sequential extraction method were used to examine the partitioning of elements in soil and identify the current elemental distribution of anthropogenic contamination. The results indicate that although a significant proportion of Ca tends to be bound with exchangeable and weak acid soluble fractions, in the hearth and house areas there is also a significant proportion held within the recalcitrant residue. Pb concentrations tend to be associated with organic matter, ammonium oxalate extractable fractions and the residue, whilst Zn generally has a more even partitioning between the six soil fractions. The implications of this for extraction methodology are element and soil specific. However, the presence of a significant proportion of anthropogenically significant elements (including Ca, Pb, Zn, Sr, and Ba) within the resistant residue suggests the use of only a weak acid or an exchangeable fraction extraction would result in the loss of information from contamination resulting from former human activity. Hence, a total or pseudo-total extraction method is recommended for this type of study.     

First-instar monarch larval growth and survival on milkweeds in southern California: effects of latex, leaf hairs and cardenolides

Growth rate and survival of first-instar larvae of Danaus plexippus, a milkweed specialist, depended on milkweed species, and was related to the amount of latex produced from wounds, leaf cardenolide concentrations and the presence of leaf hairs. Larval growth was more rapid and survival was higher on leaves of Asclepias californica with experimentally reduced latex, and this species has characteristically high latex, low- to mid-range cardenolide concentrations, and very hirsute leaves. Similarly, growth was higher on reduced latex leaves of both A. eriocarpa (a high latex/high cardenolide, hirsute species) and A. erosa (glabrous fleshy leaves, high latex/high cardenolides). There were no differences in either survival or growth rate between larvae on reduced latex or control leaves of the low latex/low cardenolide A. fascicularis with soft glabrous leaves and both survival and growth rate were higher on this species than the other species tested. Larval growth rates on leaves with reduced latex were similar among ten milkweed species tested to date but differed from growth rates on intact leaves suggesting that latex and possibly included cardenolides are both important in first-instar monarch larval growth, development and survival. We show for a range of ecologically important milkweeds that experiments on cut plant material (no latex outflow) lead to higher growth rates compared to intact plants. Such laboratory assays based on detached leaves will be misleading if the objective is to determine the impact of treatments such as Bt-maize pollen on monarchs on field plants.     

The dominance of seismic signaling and selection for signal complexity in Schizocosa multimodal courtship displays

Schizocosa wolf spiders show tremendous diversity in courtship complexity, with different species employing varying numbers of components within and across sensory modalities. Using a comparative approach, we investigate the importance of each signaling modality in the courtship display of five Schizocosa species (three stridulating and two drumming) by assessing mating success under manipulated signaling environments. Irrespective of the degree of male ornamentation, the three stridulating species exhibit a dependence on the seismic, but not visual, signaling environment for mating success. Mating was independent of signaling environment for the two drumming species. We next ask whether the degree to which each species depends upon a signaling modality for mating (i.e., modality importance) is correlated with the estimated modality-specific signal complexity. We first calculate effect sizes for the influence of seismic versus visual signaling environments on the likelihood to mate for ten Schizocosa species and then use an element-counting approach to calculate seismic and visual signal complexity scores. We use a phylogenetic regression analysis to test two predictions: (1) the importance of seismic signaling is correlated with seismic signal complexity and (2) the importance of visual signaling is correlated with visual signal complexity. We find a significant relationship between visual signal importance and visual signal complexity, but no relationship between seismic signal importance and seismic signal complexity. Finally, we test the hypothesis that selection acts on complexity per se by determining whether seismic and visual signal complexity is correlated across species. We find support for this hypothesis in a significant relationship between seismic and visual signal complexity.