Small mammal abundance and habitat relationships on deciduous forested sites with different susceptibility to gypsy moth defoliation

Yahner, Richard H.; Smith, Harvey R.

doi:10.1007/bf02393842

Cited by 18 publications

(18 citation statements)

References 26 publications

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“…There is considerable empirical evidence in our system that densities of generalist predators are higher at lower elevations (Campbell 1981;Smith 1983Smith , 1985Yahner and Smith 1991;Brooks et al 1998), yet we did not find a simple positive relationship between elevation and the strength of cyclicity in gypsy moth outbreaks. From low to intermediate elevation, outbreak cyclicity increased with increasing elevation.…”

Section: Discussioncontrasting

confidence: 64%

“…However, above intermediate predator densities, we found that a predator exhibiting a type-II functional response could cause gypsy moth density to remain extremely low for long periods of time and reduce cyclicity in host-pathogen oscillations. Given these findings, the elevational gradient in generalist predator (small mammal) density (Campbell 1981;Smith 1983Smith , 1985Yahner and Smith 1991;Brooks et al 1998) and the rate at which they feed on gypsy moth pupae (i.e., lower rate of feeding at high elevation; Smith 1989) could underlie the elevational patterns of cyclicity displayed by gypsy moth populations.…”

Section: Discussionmentioning

confidence: 95%

“…Densities of these generalists are typically lower in higher-elevation sites likely because shrub and herbaceous layers are not well developed on xeric slopes and ridgetops (Campbell 1981;Smith 1983Smith , 1985Yahner and Smith 1991;Brooks et al 1998). For example, in a 16-year survey of small mammals in Vermont, USA, recaptures of small mammals [chiefly Peromyscus leucopus Rafinesque (white-footed mouse), Myodes gapperi Vigors (southern red-backed vole), and various shrews] were 12.1 and 14.5% higher at low-than at mid-and high-elevation sites, respectively (Brooks et al 1998).…”

Section: Introductionmentioning

confidence: 99%

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Elevational gradient in the cyclicity of a forest‐defoliating insect

Haynes¹,

Liebhold

Johnson

2012

Population Ecology

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Observed changes in the cyclicity of herbivore populations along latitudinal gradients and the hypothesis that shifts in the importance of generalist versus specialist predators explain such gradients has long been a matter of intense interest. In contrast, elevational gradients in population cyclicity are largely unexplored. We quantified the cyclicity of gypsy moth populations along an elevational gradient by applying wavelet analysis to spatially referenced 31-year records of defoliation. Based on geographically weighted regression and nonlinear regression, we found either a hump-shaped or plateauing relationship between elevation and the cyclicity of gypsy moth populations and a positive relationship between cyclicity and the density of the gypsy moth's preferred host-tree species. The potential effects of elevational gradients in the density of generalist predators and preferred host-tree species on the cyclicity of gypsy moth populations were evaluated with mechanistic simulation models. The models suggested that an elevational gradient in the densities of preferred host tree species could partially explain elevational patterns of gypsy moth cyclicity. Results from a model assuming a type-III functional response of generalist predators to changes in gypsy moth density were inconsistent with the observed elevational gradient in gypsy moth cyclicity. However, a model with a more realistic type-II functional response gave results roughly consistent with the empirical findings. In contrast to classical studies on the effects of generalist predators on prey population cycles, our model with a type-II functional response predicts a unimodal relationship between generalist-predator density and the cyclicity of gypsy moth populations.

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Section: Discussioncontrasting

confidence: 64%

Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Elevational gradient in the cyclicity of a forest‐defoliating insect

Haynes¹,

Liebhold

Johnson

2012

Population Ecology

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“…Consistent with this hypothesis, Johnson et al (2006a) reported that gypsy moths had a dominant 5-year period and no indication of a 10-year period in areas where oaks grow in dry soils (e.g., oak-pine forests), which tend to support low densities of generalist rodent predators (Smith 1985;Yahner and Smith 1991;Liebhold et al 1995).…”

Section: D)mentioning

confidence: 78%

“…Differences in periodicity among forest stands may be caused by intrinsic differences in forest communities such as differences in the availability of gypsy moth hosts, densities of generalist predators (Campbell and Sloan 1977;Elkinton and Liebhold 1990), or the covariation of these or other factors. For example, oak species dominate as the moth's most preferred hosts in North America but they also provide the main winter food source (acorns) for generalist predator rodents such as Peromyscus leucopus, which prey opportunistically upon gypsy moth pupae (Smith 1985;Yahner and Smith 1991). Given the potential for scale-dependent population behavior and spatial covariation in factors influencing forest insect population growth, advancing our understanding of forest insect outbreaks will require spatially explicit analyses and a multi-scale approach.…”

Section: Introductionmentioning

confidence: 99%

Spatial analysis of harmonic oscillation of gypsy moth outbreak intensity

2008

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Outbreaks of many forest-defoliating insects are synchronous over broad geographic areas and occur with a period of approximately 10 years. Within the range of the gypsy moth in North America, however, there is considerable geographic heterogeneity in strength of periodicity and the frequency of outbreaks. Furthermore, gypsy moth outbreaks exhibit two significant periodicities: a dominant period of 8-10 years and a subdominant period of 4-5 years. In this study, we used a simulation model and spatially referenced time series of outbreak intensity data from the Northeastern United States to show that the bimodal periodicity in the intensity of gypsy moth outbreaks is largely a result of harmonic oscillations in gypsy moth abundance at and above a 4 km(2) scale of resolution. We also used geographically weighted regression models to explore the effects of gypsy moth host-tree abundance on the periodicity of gypsy moths. We found that the strength of 5-year cycles increased relative to the strength of 10-year cycles with increasing host tree abundance. We suggest that this pattern emerges because high host-tree availability enhances the growth rates of gypsy moth populations.

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Spatial Synchrony of Insect Outbreaks

Liebhold

Haynes²,

Bjørnstad

2012

Insect Outbreaks Revisited

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Introduction6.3.3 Trophic interactions 119 6.4 The ubiquity of synchrony and its implications 120 Acknowledgments 122 References 122The concept of "spacial synchrony" refers to the tendency of tbe densities of spatially disjunct populations to be correlated in time (Bj0rnscad et al. 1999a, Liebhold et al. 2004. Oucbreaking forest insects offer many of the classic examples of chis phenomenon (Figure 6.1). The spatial extent of synchrony of outbreaks is probably one of the most important -yet most underappreciated -characteristics that cause certain insect species to be classified as noxious pests. Locally eruptive population behavior alone would rarely qualify a species for "outbreak" status. Rather, regionalization of eruptions is what elevates ecologicaJ and socioeconomic impacts of certain species co bigh levels of concern, which gives chem pest status. Consider for example the contrast between the fall web worm, Hyphantria cunea, and the gypsy 1110th, Lymantria dispar (Figure 6.2). The former can reach very high localized densities and denude branches of leaves, but in North America this defoliation is typically limited to isolated colonies on different branches on different trees over several years. Due to the highly localized narure of its d::image, this species is nor considered a major pest in the eastern United States. The gypsy moth in contrast is considered a highly noxious species because its defoliation is extremely synchronized, extending continuously over thousands of hectares in a single year.Outbreaks of forest insects can bave vast impacts on ecosystem functions. These effects include nitrogen leacbing, carbon sequestration, and alteration of fire regimes (

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Small mammal abundance and habitat relationships on deciduous forested sites with different susceptibility to gypsy moth defoliation

Cited by 18 publications

References 26 publications

Elevational gradient in the cyclicity of a forest‐defoliating insect

Elevational gradient in the cyclicity of a forest‐defoliating insect

Spatial analysis of harmonic oscillation of gypsy moth outbreak intensity

Spatial Synchrony of Insect Outbreaks

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