Do Spur-Throated Grasshoppers, Melanoplus spp. (Orthoptera: Acrididae), Exert Top-Down Control on Smooth Cordgrass Spartina alterniflora in Northern New England?

Johnson, David Samuel; Jessen, Brita

doi:10.1007/s12237-008-9074-3

Cited by 16 publications

(4 citation statements)

References 43 publications

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“…, Hughes ) and insects (Finke and Denno , Bertness et al. , Johnson and Jessen ) on salt marsh plants have been reported by independent researchers across a large spatial extent in the eastern United States. The generality of top‐down control of plants by herbivores shown in our synthesis is further corroborated by the prevalence of herbivores documented in large‐scale surveys of coastal wetlands (e.g., Farnsworth and Ellison , Silliman and Bortolus , Alberti et al.…”

Section: Discussionmentioning

confidence: 91%

Consumer control as a common driver of coastal vegetation worldwide

Silliman

2016

Ecological Monographs

116

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Rapid, global anthropogenic alteration of food webs in ecosystems necessitates a better understanding of how consumers regulate natural communities. We provide a global synthesis of consumer control of vegetation in coastal wetlands, where the domineering role of physical factors such as nutrient and salinity, rather than consumers, has been emphasized for decades.Using a dataset of 1748 measures of consumer effects reported in 443 experiments/observations on all continents except the Antarctica, we examine the generality of consumer control in salt marshes and mangroves globally.Our analyses show that salt marsh herbivores, including insects, snails, crabs, waterfowl, small mammals, and livestock, generally and often strongly suppress plant survival, aboveground biomass, and height, while their effects on plant density, belowground biomass, reproduction, and cover are more variable. These effects occur in forbs, grasses, and shrubs, and in both seedlings and adult plants. Herbivores additionally affect plant nutrient stoichiometry, and mediate plant interactions, though their effects on plant diversity are less consistent. Higher trophic levels also affect plants, as predators facilitate plant growth through trophic cascades that suppress grazer abundance and grazing rate. In mangroves, there are also signs of consumer This article is protected by copyright. All rights reserved. control, though the relatively few studies available have often focused on mangrove propagules and seedlings rather than adults.Our analyses further reveal that the strength of consumer control is regulated by many physical factors. Nutrient, disturbance, and flooding, for example, amplify the negative effects of herbivores. Along latitudinal gradients, increased temperature enhances the negative effects of ectothermic herbivores, but has no effect on those of endothermic herbivores. Consumer control of coastal plants is also apparent across study methodologies: in field and laboratory settings, in observational studies, in consumer exclusion and addition experiments, in natural and

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Section: Discussionmentioning

confidence: 91%

Consumer control as a common driver of coastal vegetation worldwide

Silliman

2016

Ecological Monographs

116

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“…Importantly, a comparison of these characteristics did not identify significant differences between sites (see Appendix for detailed results). We did not monitor herbivore abundance within gardens because grazing is low at these sites (Johnson et al., 2016) and consumer regulation of Spartina is weak in this system (Johnson & Jessen, 2008). In addition, we observed almost no grazing damage on experimental plants, so herbivory is unlikely to differ between sites or among gardens.…”

Section: Methodsmentioning

confidence: 99%

Short‐ and long‐term effects of nutrient enrichment on salt marsh plant production and microbial community structure

et al. 2021

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1. Nutrient enrichment impacts ecosystems globally. Population history, especially past resource environments, of numerically dominant plant species may affect their responses to subsequent changes in nutrient availability. Eutrophication can also alter plant-microbe interactions via direct effects on associated microbial communities or indirect effects on dominant species' biomass production/allocation as a result of modified plant-soil interactions.2. We combined a greenhouse common garden and a field reciprocal transplant of a salt marsh foundation species (Spartina alterniflora) within a long-term, wholeecosystem, nutrient-enrichment study to determine whether enrichment affects plant production and microbial community structure differently depending on plant population history. For the greenhouse portion, we collected 20 S. alterniflora genotypes-10 from an enriched creek that had received elevated nutrient inputs for 10 years and 10 from an unenriched reference creek-and reared them in a common garden for 1 year. For the field portion, we conducted a 2-year, fully crossed reciprocal transplant experiment with two gardens each at the enriched and unenriched sites; we examined the effects of source site (i.e. population history), garden site and plant genotype.3. After 2 years, plants in enriched gardens had higher above-ground biomass and altered below-ground allocation compared to plants in unenriched gardens.However, performance also depended on plant population history: plants from the enriched site had decreased above-ground and rhizome production compared to plants from the unenriched site, most notably in unenriched gardens. In addition, almost all above-and below-ground traits varied depending on plant genotypic identity.4. Effects of nutrient enrichment on the associated microbial community were also pronounced. Following 1 year in common garden, microbial community structure varied by plant population history and S. alterniflora genotypic identity. However, at the end of the reciprocal transplant, microbial communities differed primarily between enriched and unenriched gardens. 5. Synthesis. Nutrient enrichment can impact plant foundation species and associated soil microbes in the short term. Most importantly, nutrient enrichment can

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“…Although EOSL is widely used as a proxy for aboveground production, it can underestimate net aboveground production by up to 15% because it does not account for tissue lost due to factors such as herbivory, self‐thinning, or leaf senescence (Nixon and Oviatt ). Herbivory in current‐study marshes, however, is low (Johnson and Jessen ) and seasonal stem loss through self‐thinning is ~10–15% of mid‐August EOSL (Chaisson ). EOSL was estimated for each transect as stem densities standardized to m −2 multiplied by corresponding mean shoot mass as described previously.…”

Section: Methodsmentioning

confidence: 99%

Saltmarsh plant responses to eutrophication

Johnson¹,

Warren

Deegan

et al. 2016

Ecological Applications

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Abstract. In saltmarsh plant communities, bottom-up pressure from nutrient enrichment is predicted to increase productivity, alter community structure, decrease biodiversity, and alter ecosystem functioning. Previous work supporting these predictions has been based largely on short-term, plot-level (e.g., 1-300 m 2 ) studies, which may miss landscape-level phenomena that drive ecosystem-level responses. We implemented an ecosystem-scale, nine-year nutrient experiment to examine how saltmarsh plants respond to simulated conditions of coastal eutrophication. Our study differed from previous saltmarsh enrichment studies in that we applied realistic concentrations of nitrate (70-100 μM NO 3 − ), the most common form of coastal nutrient enrichment, via tidal water at the ecosystem scale (~60,000 m 2 creeksheds). Our enrichments added a total of 1,700 kg N·creek −1 ·yr −1 , which increased N loading 10-fold vs. reference creeks (low-marsh, 171 g N·m −2 ·yr −1 ; high-marsh, 19 g N·m −2 ·yr −1 ). Nutrients increased the shoot mass and height of low marsh, tall Spartina alterniflora; however, declines in stem density resulted in no consistent increase in aboveground biomass. High-marsh plants S. patens and stunted S. alterniflora did not respond consistently to enrichment. Nutrient enrichment did not shift community structure, contrary to the prediction of nutrient-driven dominance of S. alterniflora and Distichlis spicata over S. patens. Our mild responses may differ from the results of previous studies for a number of reasons. First, the limited response of the high marsh may be explained by loading rates orders of magnitude lower than previous work. Low loading rates in the high marsh reflect infrequent inundation, arguing that inundation patterns must be considered when predicting responses to estuarine eutrophication. Additionally, we applied nitrate instead of the typically used ammonium, which is energetically favored over nitrate for plant uptake. Thus, the form of nitrogen enrichment used, not just N-load, may be important in predicting plant responses. Overall, our results suggest that when coastal eutrophication is dominated by nitrate and delivered via flooding tidal water, aboveground saltmarsh plant responses may be limited despite moderate-to-high water-column N concentrations. Furthermore, we argue that the methodological limitations of nutrient studies must be considered when using results to inform management decisions about wetlands.

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Do Spur-Throated Grasshoppers, Melanoplus spp. (Orthoptera: Acrididae), Exert Top-Down Control on Smooth Cordgrass Spartina alterniflora in Northern New England?

Cited by 16 publications

References 43 publications

Consumer control as a common driver of coastal vegetation worldwide

Consumer control as a common driver of coastal vegetation worldwide

Short‐ and long‐term effects of nutrient enrichment on salt marsh plant production and microbial community structure

Saltmarsh plant responses to eutrophication

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