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"Walker, Janet"
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Effects of burrowing crabs on coastal sediments and their functions: A systematic meta‐analysis
Burrowing ecosystem engineers, such as termites, crabs, marmots, and foxes, can profoundly affect the biological structure and ecosystem functions of their environments. However, the relative importance of the effects of burrowing engineers on sediments are challenging to predict and are expected to be influenced by engineer density, engineer functional traits (e.g., burrow morphology), and environmental conditions (e.g., geomorphology, vegetation presence). To develop robust hypotheses predicting the impacts of burrowing ecosystem engineers, we conducted a systematic meta‐analysis evaluating the effects of burrowing crabs on sediment properties, nutrient stocks, and ecosystem functions in soft‐sediment coastal habitats (e.g., salt marshes, mangrove forests, tidal flats). Additionally, we tested the impacts of crab burrow density, burrowing crab superfamily (a proxy for crab burrow morphology and diet), and biotic conditions (i.e., vegetation) on the effects of burrowing crab engineers on coastal sediments. Burrowing crabs rework and oxygenate sediments and accelerate rates of nutrient cycling (i.e., nitrification and CO2 flux). However, the magnitude and direction of burrowing crab effects depend on burrowing crab superfamily, the presence of vegetation, and their interaction. Crab burrow density did not consistently predict burrowing engineer effects on sediments. Future efforts need to focus on implementing rigorous manipulative experiments to assess crab ecosystem engineering effects, since methodological variation has hindered efforts to generalize their effects. Our findings suggest that crab engineering effects are predictable across environmental contexts, and understanding the context dependency of crab engineering effects may promote the management and restoration of the critical ecosystem services that are mediated by crab engineers.
Journal Article
Predicting burrowing crab impacts on salt marsh plants
Burrowing animals profoundly influence plant communities, and changes in the burrower and plant communities together with changing abiotic parameters can shift the influence of burrowers on plants. However, we lack an ability to predict when, where, and how burrowers will influence vegetation. To begin to understand how naturally, varying environmental conditions influence the impacts of burrowers, we need to examine how burrower impacts on marsh plants differ across sites differing in environmental conditions. We manipulated crab presence for multiple years and measured the responses of the dominant plants, Pacific cordgrass (Spartina foliosa) and perennial pickleweed (Sarcocornia pacifica), at three sites in northern California and two sites in southern California. Southern California (Point Conception, CA, to the U.S.–Mexico border) experiences higher air and water temperatures, lower precipitation, and higher porewater salinity levels. Combining data from these field studies with laboratory studies allowed us to generate predictions about burrowing crab effects in salt marshes. Our models included (1) an estimate of grazing pressure on marsh plants by the dominant burrowing crab (Pachygrapsus crassipes) and (2) several soil biogeochemical measurements. Crab effects varied from strongly positive to strongly negative and depended upon estimated crab grazing pressure and edaphic conditions (salinity, ammonium, and nitrate). Relative to crabs at other sites, crabs enhanced cordgrass at sites with intermediate levels of ammonium and extreme salinities. The dependence of crab effects on edaphic conditions suggests that projected interannual variability in temperature, precipitation, and nutrients could lead to more temporally variable impacts of crabs on cordgrass. Understanding the environmental controls on these interactions will help promote cordgrass productivity and stabilize salt marsh ecosystems.
Journal Article
Local and regional variation in effects of burrowing crabs on plant community structure
Burrowing animals can profoundly influence the structure of surrounding communities, as well as the performance of individual species. Changes in the community structure of burrowing animals or plants together with changing abiotic parameters could shift the influence of burrowers on surrounding habitats. For example, prior studies in salt marshes suggest that fiddler crabs stimulate cordgrass production, but leaf-grazing crabs suppress cordgrass production. Unfortunately, testing this prediction and others are impeded because few studies have examined crab impacts on the plant community and across multiple sites, multiple years, or both. This challenges our ability to predict how burrowing animals will influence plant community structure, and when and where these impacts will occur. We manipulated the densities of the dominant burrowing crabs in plant assemblages dominated by Pacific cordgrass (Spartina foliosa) and perennial pickleweed (Sarcocornia pacifica) at three sites in southern California for three years (2016, 2017, 2018). Crab impacts on plant community structure differed among each of our three sites. In contrast to our predictions, (1) leaf-grazing crabs (Pachygrapsus crassipes) had positive effects on cordgrass cover at one site and no effect on cordgrass production at a nearby site in the same marsh and (2) fiddler crabs (Uca crenulata) did not stimulate cordgrass production at another marsh. Because crabs affected traits of cordgrass, but not pickleweed, in the direction consistent with changes in cordgrass cover, we propose that marsh-specific crab effects on community structure were largely mediated through changes in cordgrass, as opposed to pickleweed. Importantly, crabs facilitated cordgrass during marsh-wide cordgrass loss, suggesting that crabs may mitigate environmental stress for this ecologically important plant. Because cordgrass abundance can be a critical measure of marsh functioning and is often a restoration target, we suggest that managing cordgrass populations would benefit from additional information about crab populations and their impacts among years, and among and within marshes.
Journal Article
A Theory of Change for Positive Developmental Approaches to Improving Outcomes Among Emerging Adults with Serious Mental Health Conditions
Recent evidence attests to the shortcomings of typical services for improving outcomes among emerging adults with serious mental health conditions (SMHCs). Researchers and providers have responded by developing new programs and interventions for meeting the unique needs of these young people. A significant number of these programs and interventions can be described as taking a positive developmental approach, which is informed by a combination of theoretical sources, including theories of positive development, self-determination, ecological systems, and social capital. To date, however, there has been no comprehensive theoretical statement describing how or why positive change should occur as a result of using a positive developmental approach when intervening with this population. The goal of this article is to propose a general model that “backfills” a theory behind what appears to be an effective and increasingly popular approach to improving outcomes among emerging adults with SMHCs.
Journal Article
Genetic Diversity and Clonal Structure of Spartina alterniflora in a Virginia Marsh
We asked how genetic diversity of Spartina alterniflora (Smooth Cordgrass) partitions across multiple spatial scales in mid-Atlantic salt marshes. We analyzed samples from 5 Virginia marshes, spanning ∼ 35 km of coastline, using microsatellite markers to examine genetic diversity and genotype clustering. In a single marsh, nested spatial analysis of the genotypes allowed indirect evaluation of colonization dynamics. Samples collected ≥10 m apart had clonal and allelic diversity levels similar to those of other geographic locations; however, genotypic richness and evenness of samples collected 0.2 and 1.0 m apart were reduced. Sampling scale had little effect on allelic diversity. Expected heterozygosity exceeded observed heterozygosity values at all sites and spatial scales, suggesting Smooth Cordgrass inbreeding is common in these marshes. We hypothesize that the observed spatial patterns indicate there is genetic dominance of a few, well-adapted clones balanced by sexual reproduction and recruitment, especially after disturbance, thereby creating genetically diverse and potentially resilient marshes.
Journal Article
Factor Structure, Reliability, and Validity of the Wraparound Fidelity Index Short Form (WFI-EZ)
Wraparound care coordination has been demonstrated to promote positive mental health, residential, and cost outcomes for children and youth with serious emotional and behavioral disorders (SEBD) and their families. However, research also shows that positive outcomes are dependent on adequacy of Wraparound fidelity. The current study presents results from a series of studies that collectively assessed the factor structure, reliability, and validity of the Wraparound Fidelity Index, Short Form (WFI-EZ), a four section, multi-informant, self-report measure. Analyses of a sample of 10,955 caregivers of youth who received Wraparound and completed the WFI-EZ found a four-factor solution that aligned well with previous theories of change for Wraparound, with factors focused on team membership, team process, inclusion of natural supports, and intermediate outcomes, including increased family assets and more effective services and supports. Cronbach’s alpha was 0.90 for the full index and acceptable for all four empirically derived factors (α = 0.61–0.91); preliminary test-retest reliability data for the composite WFI-EZ fidelity index drawn from two small samples was found to be high for caregivers (r = 0.94) and moderate for care coordinators (r = 0.72). Results of known-groups analyses found that WFI-EZ scores discriminated groups theoretically expected to differ on Wraparound fidelity, including whether basic elements of Wraparound were provided and whether provider organizations were measured as having high versus low supports for Wraparound. Results indicate the WFI-EZ is a reliable and valid measure of Wraparound fidelity, while also pointing to opportunities for future refinement, further research, and opportunities for improving Wraparound training and implementation support.
Highlights
The Wraparound Fidelity Index, Short Form (WFI-EZ) was shown to be a reliable and valid fidelity measure.
An underlying factor structure of the WFI-EZ was found that aligns with past theory on Wraparound that emphasizes the importance of Wraparound team membership, team process, and two routes to positive family outcomes: increased family assets and more effective services and supports.
Wraparound provider factors such as leadership and staff morale were found to be associated with practice fidelity and caregiver satisfaction.
The current study points to potential future refinements, including reduction in the number of items and revision of scoring rules.
Journal Article
Researcher effects on the biological structure and edaphic conditions of field sites and implications for management
Field studies are necessary for understanding natural processes in spite of the human‐induced disturbances they cause. While researchers acknowledge these effects, no studies have empirically tested the direct (e.g., harvesting plants) and indirect (i.e., trampling) effects of researcher activities on biological structure and edaphic conditions. We leveraged field studies in Alabama and California to monitor the recovery of tidal marshes following research activities. Researcher effects on animals, plants, and sediment conditions remained prevalent almost one year after the disturbance ended. For instance, trampled plots had 14%–97% lower plant cover than undisturbed plots after >10 months of recovery. Researcher effects also impacted plant composition, leading to increased subordinate species abundance. We encourage field researchers to adopt strategies that reduce their scientific footprints, including reducing field visits, limiting field team size, and considering ways to limit potential environmental impacts during study design.
Journal Article
Disaster Media: Bending the Curve of Ecological Disruption and Moving toward Social Justice
This essay introduces a special stream of Media+Environment focused on “disaster media.” In the process, the authors conceptualize this term in relation to “natural” and other disasters, including the COVID-19 pandemic, and explore how understandings of “disaster media” are embedded within several areas of humanities-based film and media scholarship. Writing from the social ecological premise that consequences of disasters stem in large part from systemic actions, the introduction develops three general arguments about disaster media as an analytic. First, disasters cause people to rethink what “media” are and to contend with the fact that, especially during disasters, media are constantly changing and being updated; they also escape the screen and sculpt the environment (media are not only representational but also affective and infrastructural). Second, because they come to the fore in relation to crisis situations, disaster media help expose structural inequalities; practices of relief and reform need to happen and can be facilitated (or inhibited) by mediatic means. Finally, disaster media need to be considered in relation to the multiple temporalities of climate disruption (from the longue durée of glacial flow to uncertain and sudden extreme weather). Discussing these issues, the authors also introduce pieces in the stream that are focused on humanitarian drone interventions and glacier-melt artworks.
Journal Article