Interactions between invasive herbivores and their long-term impact on New England hemlock forests

Gómez, Sara; Gonda‐King, Liahna; Orians, Colin M.; Orwig, David A.; Panko, R.; Radville, Laura; Soltis, Nicole E.; Thornber, Carol S.; Preisser, Evan L.

doi:10.1007/s10530-014-0757-3

Cited by 18 publications

(17 citation statements)

References 39 publications

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“…Scale was introduced from Asia in 1908 and is less harmful to hemlocks than adelgid. Both invasive insects were undergoing northwards range expansion in the eastern U.S.A. during the study period, 1997–2011 (Gómez et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Initial assessment of stands occurred in 1997–1998 (Connecticut only; Orwig, Foster, & Mausel, ) and –2004 (Massachusetts only; Orwig et al, ). All stands were subsequently assessed in 2005, 2007, 2009 and 2011 (Gómez et al, , and references within). Ordinal abundance was assigned to one of four ordered categories as described by Gómez et al () and Table .…”

Section: Methodsmentioning

confidence: 99%

“…All stands were subsequently assessed in 2005, 2007, 2009 and 2011 (Gómez et al, , and references within). Ordinal abundance was assigned to one of four ordered categories as described by Gómez et al () and Table . In this example,

Y_{i, t, j}^{(s)}

denoted the ordinal measure of abundance for stand i , tree j , in year t of species s , where s = 1 for adelgid and s = 2 for scale.…”

Section: Methodsmentioning

confidence: 99%

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Joint species distribution modelling for spatio‐temporal occurrence and ordinal abundance data

Schliep

Lany

Zarnetske

et al. 2017

Global Ecol Biogeogr

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Aim: Species distribution models are important tools used to study the distribution and abundance of organisms relative to abiotic variables. Dynamic local interactions among species in a community can affect abundance. The abundance of a single species may not be at equilibrium with the environment for spreading invasive species and species that are range shifting because of climate change. Innovation:We develop methods for incorporating temporal processes into a spatial joint species distribution model for presence/absence and ordinal abundance data. We model non-equilibrium conditions via a temporal random effect and temporal dynamics with a vectorautoregressive process allowing for intra-and interspecific dependence between co-occurring species. The autoregressive term captures how the abundance of each species can enhance or inhibit its own subsequent abundance or the subsequent abundance of other species in the community and is well suited for a 'community modules' approach of strongly interacting species within a food web. R code is provided for fitting multispecies models within a Bayesian framework for ordinal data with any number of locations, time points, covariates and ordinal categories.Main conclusions: We model ordinal abundance data of two invasive insects (hemlock woolly adelgid and elongate hemlock scale) that share a host tree and were undergoing northwards range expansion in the eastern U.S.A. during the period 1997-2011. Accounting for range expansion and high inter-annual variability in abundance led to improved estimation of the species-environment relationships. We would have erroneously concluded that winter temperatures did not affect scale abundance had we not accounted for the range expansion of scale. The autoregressive component revealed weak evidence for commensalism, in which adelgid may have predisposed hemlock stands for subsequent infestation by scale. Residual spatial dependence indicated that an unmeasured variable additionally affected scale abundance. Our robust modelling approach could provide similar insights for other community modules of co-occurring species.biotic interactions, coregionalization, invasive species, Markov chain Monte Carlo, rank probability scores, vector autoregression | I NTR OD U CTI ONSpecies distribution models are commonly used in basic and applied ecological research to study the factors that define the distribution and abundance of organisms. They are used to quantify species' relationships with abiotic conditions, to predict species' response to land-use and climatic change and to identify potential conservation areas (Guisan & Zimmermann, 2000). Traditionally, species distribution models correlate static observations of the occurrence (presence and absence) or abundance of a species with abiotic variables. Occurrence and abundance of a species, however, can also change through time and across space through colonization and may not be at equilibrium

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Y_{i, t, j}^{(s)}

denoted the ordinal measure of abundance for stand i , tree j , in year t of species s , where s = 1 for adelgid and s = 2 for scale.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Joint species distribution modelling for spatio‐temporal occurrence and ordinal abundance data

Schliep

Lany

Zarnetske

et al. 2017

Global Ecol Biogeogr

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“…It is currently debated whether EHS contributes to hemlock decline or, conversely, might mediate or lessen the effects of HWA through competitive interactions (Preisser and Elkinton , Gomez et al. ). Regardless, the abundance and dominance of hemlock in many eastern U.S. forests have already declined substantially and the species is expected to be lost from many areas in coming decades.…”

Section: Introductionmentioning

confidence: 99%

Decline of a foundation tree species due to invasive insects will trigger net release of soil organic carbon

Fassler

Bellemare

2018

Ecosphere

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Citation: Ignace, D. D., A. Fassler, and J. Bellemare. 2018. Decline of a foundation tree species due to invasive insects will trigger net release of soil organic carbon. Ecosphere 9(8):Abstract. Eastern U.S. forests are witnessing an ecologically disruptive decline in one of the region's distinctive foundation tree species, the eastern hemlock (Tsuga canadenis). The exotic insect pests hemlock woolly adelgid (Adelges tsugae, HWA) and elongate hemlock scale (Fiorinia externa) have greatly altered many forest ecosystems previously dominated by this important evergreen conifer. The consequences for ecosystem processes are far reaching because hemlock is often replaced by deciduous tree species, such as black birch (Betula lenta), which have strongly divergent effects on forest floor microenvironments and nutrient cycling. We took advantage of an accidental experiment initiated by patch-level timber harvesting 30 yr ago to investigate how the removal of hemlock, and its replacement by deciduous trees, has affected leaf litter characteristics, soil organic layer mass, C:N content, and soil respiration rates. We also contrasted these areas to nearby forest plots where deciduous B. lenta has been dominant for almost a century. The inclusion of healthy, intact hemlock stands in the design, and the close proximity of plots, allowed for a powerful space-for-time approach to detect ecosystem changes that are likely to occur across the broader landscape with HWA-induced hemlock loss in coming years. Three years of data collection from a series of plots in hemlock, young birch, and mature birch stands revealed dramatic differences in soil carbon pools and cycling. Between forests dominated by hemlock vs. mature birch, we saw a significant decrease in soil organic layer mass and in the C:N of the remaining organic material. Although hemlock and young birch stands showed no significant differences in soil respiration rates, mature birch stands had significantly higher soil respiration rates throughout the entire growing season, regardless of wet or dry years. Our results suggest that the carbon pool in the forest floor is likely to mobilize through greater decomposition with a 6.89 decline in soil organic layer C storage as hemlocks are replaced by deciduous trees, leading to a potential net release of~4.5 tons C per hectare. We conclude that the ramifications of this change for carbon storage could be extensive, but may take decades to manifest.

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“…, , Gomez et al. ), the rate and intensity of adelgid‐related mortality for different demographic stages of hemlock (Preisser et al. , Kantola et al.…”

Section: Introductionmentioning

confidence: 99%

When a foundation crumbles: forecasting forest dynamics following the decline of the foundation species Tsuga canadensis

et al. 2017

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Abstract. In the forests of northeastern North America, invasive insects and pathogens are causing major declines in some tree species and a subsequent reorganization of associated forest communities. Using observations and experiments to investigate the consequences of such declines are hampered because trees are long-lived. Simulation models can provide a means to forecast possible futures based on different scenarios of tree species decline, death, and removal. Such modeling is particularly urgent for species such as eastern hemlock (Tsuga canadensis), a foundation species in many northeastern forest regions that is declining due to the hemlock woolly adelgid (Adelges tsugae). Here, we used an individual-based forest simulator, SORTIE-ND, to forecast changes in forest communities in Central Massachusetts over the next 200 yr under a range of scenarios: a no-adelgid, status quo scenario; partial resistance of hemlock to the adelgid; adelgid irruption and total hemlock decline over 25 yr, adelgid irruption and salvage logging of hemlock trees; and two scenarios of preemptive logging of hemlock and hemlock/white pine. We applied the model to six study plots comprising a range of initial species mixtures, abundances, and levels of hemlock dominance. Simulations indicated that eastern white pine, and to a lesser extent black birch and American beech, would gain most in relative abundance and basal area following hemlock decline. The relative dominance of these species depended on initial conditions and the amount of hemlock mortality, and their combined effect on neighborhood-scale community dynamics. Simulated outcomes were little different whether hemlock died out gradually due to the adelgid or disappeared rapidly following logging. However, if eastern hemlock were to become partially resistant to the adelgid, hemlock would be able to retain its dominance despite substantial losses of basal area. Our modeling highlights the complexities associated with secondary forest succession due to ongoing hemlock decline and loss. We emphasize the need both for a precautionary approach in deciding between management intervention or simply doing nothing in these declining hemlock forests, and for clear aims and understanding regarding desired community-and ecosystem-level outcomes.

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Interactions between invasive herbivores and their long-term impact on New England hemlock forests

Cited by 18 publications

References 39 publications

Joint species distribution modelling for spatio‐temporal occurrence and ordinal abundance data

Joint species distribution modelling for spatio‐temporal occurrence and ordinal abundance data

Decline of a foundation tree species due to invasive insects will trigger net release of soil organic carbon

When a foundation crumbles: forecasting forest dynamics following the decline of the foundation species Tsuga canadensis

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