Vegetation and Invertebrate Community Response to Eastern Hemlock Decline in Southern New England

Laura L. Ingwell; Mailea Miller-Pierce; R. Talbot Trotter; Evan L. Preisser

doi:10.1656/045.019.0402

Eastern hemlock (Tsuga canadensis) regeneration in the presence of hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa)

Canadian Journal of Forest Research ◽

10.1139/x11-155 ◽

2011 ◽

Vol 41 (12) ◽

pp. 2433-2439 ◽

Cited By ~ 21

Author(s):

Evan L. Preisser ◽

Mailea R. Miller-Pierce ◽

Jacqueline Vansant ◽

David A. Orwig

Keyword(s):

New England ◽

Tsuga Canadensis ◽

Hemlock Woolly Adelgid ◽

Adelges Tsugae ◽

Eastern Hemlock ◽

Invasive Pest ◽

Seedling Density ◽

Southern New England ◽

Elongate Hemlock Scale ◽

Fiorinia Externa

The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive hemipteran that poses a major threat to eastern hemlock (Tsuga canadensis (L.) Carrière) forests in the United States. We conducted three surveys over a five-year period that assessed the density of hemlock woolly adelgid (HWA) and a second invasive pest, the elongate hemlock scale (EHS; Fiorinia externa Ferris), overstory hemlock mortality, and hemlock regeneration in ~140 hemlock stands (mean size, 44 ha; range, 7–305 ha) within a 7500 km2 north–south transect of southern New England (USA). In each stand, we rated HWA and EHS density on 50 hemlock trees using a 0–3 scale (0, none; 1, 1–10 organisms/m branch; 2, 11–100 organisms/m branch; 3, >100 organisms/m branch). Data on the presence or absence of regeneration were taken in 2005; in 2007 and 2009, we quantitatively assessed regeneration by counting the number of hemlock seedlings in three 16 m2 plots per stand. In 2005, 81% of sampled stands had HWA, 72% had EHS, and 66% had hemlock regeneration. In 2007, 86% of sampled stands had HWA, 79% had EHS, and 46% had hemlock regeneration. In 2009, 91% of stands had HWA, 87% had EHS, and 37% had hemlock regeneration. The proportion of stands with hemlock regeneration declined 46% between 2005 and 2009, and hemlock seedling density declined 71% between 2007 and 2009. A best-fit model selection algorithm found that this decrease was inversely correlated with stand-level adelgid density. There was no correlation between the change in seedling density and stand-level density of the elongate hemlock scale. The apparent decline in regeneration suggests that the ecosystem-level changes currently occurring in southern New England may be difficult to reverse.

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14,000 Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southeastern Massachusetts

Quaternary Research ◽

10.1006/qres.1999.2120 ◽

2000 ◽

Vol 53 (3) ◽

pp. 352-368 ◽

Cited By ~ 58

Author(s):

Paige E. Newby ◽

Peter Killoran ◽

Mahlon R. Waldorf ◽

Bryan N. Shuman ◽

Robert S. Webb ◽

...

Keyword(s):

New England ◽

Water Level ◽

Sediment Accumulation ◽

Vegetation Development ◽

Peat Accumulation ◽

Southern New England ◽

Hemlock Decline ◽

Pine Trees ◽

Dry Conditions ◽

Cedar Swamp

AbstractData from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between ∼10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose ∼2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.

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Decomposition of green foliage in eastern hemlock forests of southern New England impacted by hemlock woolly adelgid infestations

Canadian Journal of Forest Research ◽

10.1139/x06-012 ◽

2006 ◽

Vol 36 (5) ◽

pp. 1331-1341 ◽

Cited By ~ 35

Author(s):

Richard C Cobb ◽

David A Orwig ◽

Steve Currie

Keyword(s):

Soil Moisture ◽

New England ◽

Mass Loss ◽

Organic Soil ◽

Hemlock Woolly Adelgid ◽

Adelges Tsugae ◽

Eastern Hemlock ◽

Functional Changes ◽

Southern New England ◽

Crown Health

This study examined the impacts of hemlock woolly adelgid (Adelges tsugae Annand) (HWA), a small, invasive insect, on foliar chemistry, forest floor microclimate, and subsequent green foliage decomposition in eastern hemlock (Tsuga canadensis (L.) Carrière) forests. We investigated the direct effects of HWA feeding and indirect changes in microclimate on foliar decomposition by incubating HWA-infested and uninfested foliage across eight eastern hemlock dominated stands in southern New England that had different histories of HWA infestation. Infested stands had much poorer average crown health (3.4 versus 1.4 crown loss ratings), higher percent open sky (10.9 ± 2.4 vs. 5.3 ± 0.5 gap light index), and lower organic soil moisture (0.83 ± 0.02 g·g1 vs. 1.06 ± 0.05 g·g1) than uninfested stands. There were no significant differences in percent C, percent N, or percent lignin for the excised foliage at the start of the study. However, after 120 days, decomposing foliage from infested trees had significantly higher N concentrations (1.83% ± 0.05% vs. 1.69% ± 0.02 %) and lower C/N ratios (29.9 ± 0.8 vs. 31.6 ± 0.2) than uninfested foliage, suggesting that HWA herbivory resulted in alterations of litter chemistry as decomposition progressed. Mass loss of common uninfested foliage was lower in uninfested hemlock stands than in infested ones (30.9% ± 0.7% vs. 34.2% ± 0.1%). These rates of mass loss were significantly correlated with microclimate factors and indicate that organic soil moisture levels are controlling decomposition in HWA-infested forests. Infestation by HWA causes virtually no direct feeding damage to foliage, but it does lead to several indirect and significant ecological and functional changes over the 10- to 20-year course of infestation and stand decline.

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Eastern Hemlock Decline in Riparian Areas from Maine to Alabama

Northern Journal of Applied Forestry ◽

10.1093/njaf/28.2.97 ◽

2011 ◽

Vol 28 (2) ◽

pp. 97-104 ◽

Cited By ~ 7

Author(s):

Daniel M. Evans ◽

W. Michael Aust ◽

C. Andrew Dolloff ◽

Ben S. Templeton ◽

John A. Peterson

Keyword(s):

New England ◽

Hemlock Woolly Adelgid ◽

Adelges Tsugae ◽

Ecosystem Dynamics ◽

Eastern Hemlock ◽

Forest Composition ◽

Mountain Range ◽

Riparian Areas ◽

Conifer Species ◽

Hemlock Decline

Abstract Eastern hemlock (Tsuga canadensis) in the Appalachian mountain range is threatened by the introduced hemlock woolly adelgid (Adelges tsugae). Potential impacts on riparian systems are great because of eastern hemlock's role as a foundation species that influences site soil, vegetation, and stream characteristics. We installed permanent research sites at 49 locations in riparian areas, from Maine to Alabama, to survey eastern hemlock health, measure stand dynamics, and predict near-term forest composition without eastern hemlock. This report summarizes the initial stand measurements from summer of 2008. We found hemlock woolly adelgid present at 25 of 49 stands from Massachusetts to Georgia, and all of these stands had some degree of hemlock decline. New England states, Ohio, western Pennsylvania, Kentucky, and Alabama had good hemlock health and no sign of hemlock woolly adelgid. Eighteen of the 49 sites had no nonhemlock conifer species in the overstory, and 30 of 49 sites had less than 5 m2 ha−1 of nonhemlock conifers. Without eastern hemlock, 25 of the stands would have more than 90% hardwood in the overstory, many of which are in the mid-Atlantic and southern states at sites dominated by shrubs in the understory such as Rhododendron maximum. Competition from shrubs may hinder stand regeneration after disturbance by hemlock woolly adelgid. On the basis of the abundance of hardwood species and lack of conifer species present in the overstory at many infested hemlock-dominated stands, these sites may convert to hardwood-dominated stands, which will affect terrestrial and aquatic ecosystem dynamics.

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