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Harvard Forest Data Archive

HF082

Ecosystem and Vegetation Response to Hemlock Logging in Southern New England 1999-2005

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Data

Overview

  • Lead: David Orwig, David Foster
  • Investigators: Richard Cobb, Matthew Kizlinski, Laura Barbash
  • Contact: David Orwig
  • Start date: 1999
  • End date: 2005
  • Status: completed
  • Location: Central Connecticut
  • Latitude: +41.4 to +41.9
  • Longitude: -73.2 to -72.2
  • Elevation:
  • Taxa: Adelges tsugae (hemlock woolly adelgid), Betula lenta (black birch), Carex (sedges), Dennstaedtia punctilobula (hayscented fern), Rubus (brambles), Tsuga canadensis (eastern hemlock)
  • Release date: 2006
  • Revisions:
  • EML file: knb-lter-hfr.82.16
  • DOI: digital object identifier
  • Related links:
  • Study type: long-term measurement
  • Research topic: conservation and management; invasive plants, pests and pathogens; regional studies
  • LTER core area: inorganic nutrients, disturbance
  • Keywords: ammonium, hemlock, hemlock woolly adelgid, nitrate, nitrification, nitrogen mineralization, timber harvest
  • Abstract:

    This study compares the magnitude and trajectory of vegetation and ecosystem function dynamics associated with the direct impact of hemlock woolly adelgid (Adelges tsugae; HWA) infestation versus the indirect consequences of HWA-induced damage in the form of salvage and pre-emptive logging of hemlock (Tsuga canadensis (L.) Carriere) forests. The study was conducted within an area extending from southern Connecticut up to and including the Connecticut River lowlands west to the Berkshire Plateauin central Massachusetts, USA. Overstory and understory vegetation and ecosystem function parameters such as decomposition and nitrogen cycling were examined in logged and unlogged portions of 10 hemlock stands varying in HWA damage intensity.

    Intensive hemlock logging generated more rapid and pronounced microenvironment and vegetation changes than chronic HWA damage. Black birch (Betula lenta L.) seedling densities and percent cover of brambles (Rubus L. spp.), sedges (Carex L. spp.) and hay-scented fern (Dennstaedtia punctilobula Michx.) were significantly higher in recent harvests versus HWA-damaged and undamaged sites. High black birch sapling densities (greater than 7000 ha –1) were common in the older harvests but not in adjacent, HWA-damaged portions of these sites. Undamaged sites had 20% more forest floor mass than HWA-damaged sites and double the mass of older cuts. Mass loss rates of cellulose paper suggest that conditions were more favorable for decomposition in the damaged and older logged sites. Recently cut sites had significantly larger inorganic N pools than undamaged forests, although total net nitrogen (N) mineralization rates were not significantly different among treatments. Nitrification rates of 0.2 kg ha-1 day-1 measured in the oldest cuts were three times greater than in HWA-damaged sites and over 200 times greater than in undamaged hemlock sites. However, resin bag capture in the older cuts was similar to amounts captured in undamaged and damaged forests, suggesting that excess nitrogen was being utilized in vegetative uptake. In contrast, relatively large amounts of ammonium and nitrate captured in recent harvests indicate higher N availability, less vegetative uptake, and a greater potential for N leaching.

    Results suggest that both the decline associated with HWA infestation and the indirect effects of HWA in the form of logging are generating profound changes in structure, composition, and ecosystem function in these forests, although at different spatial and temporal scales. Hemlock harvesting imposed more abrupt microenvironmental changes, and rapidly reduced vegetative cover while chronic HWA infestation led to gradually thinning canopies. Both disturbances led to black birch dominated forests, although logging resulted in greater amounts of shade-intolerant regeneration, higher soil pH and nitrification rates, and reduced forest floor mass. Preemptive cutting of undamaged forests may lead to greater N losses than those associated with HWA infestation or logging of deteriorated hemlock forests, due to reduced vegetative uptake. Silvicultural methods that allow for vegetation establishment prior to harvesting will likely lessen the ecological impacts of hemlock removal.

  • Methods:

    Transects were established in the most heavily cut area and in the nearest unlogged portion of each stand. Vegetation was sampled in 5 to 10 circular plots (78.5 m2) located every 20 m along these transects. Woody stems greater than or equal to 1.5 cm diameter at breast height (dbh; 1.37 m) were recorded by species, dbh, and crown position. Pre-harvest basal area was reconstructed allometrically using a regression equation relating stump diameter to dbh (y = 0.884x + 0.0003; r2=0.995) from a sample of 215 stems. Species, dbh, and probable mechanism of injury were noted for dead trees in harvest plots. Sapling (1.5 to 9.9 cm dbh) heights for each species were estimated in each plot. Herb and shrub cover was estimated in three, 1x1 m subplots located in random directions 3 m from each plot center. Seedling (less than 1.5 cm dbh) densities were also tallied in each subplot.

    Nitrogen (N) mineralization was measured with two consecutive 10-week incubations (May-July and July-September 2000) using an intact, closed-topped core method. Forest floor and mineral soil samples were homogenized by sieving (5.6 mm pore size), weighed for total mass, and sub sampled for gravimetric moisture content. Inorganic NH4-N and NO3-N concentrations were determined colorimetrically with a Lachat AE flow injection analyzer. Ion exchange resin bags were used to passively intercept inorganic N in soil solution. To characterize forest floor decomposition environment among sites, mass loss of a standard cellulose paper substrate was determined after 20 weeks.

  • Use:

    This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.

  • Citation:

    Orwig D, Foster D. 2006. Ecosystem and Vegetation Response to Hemlock Logging in Southern New England 1999-2005. Harvard Forest Data Archive: HF082.

Detailed Metadata

hf082-01: site descriptions

  1. site: site code
  2. plot.nums: range of plot numbers for each site
  3. site.name: site description
  4. trans.desc: transect description

hf082-02: environmental conditions

  1. site: site code (see site descriptions)
  2. plot: number of plot where measurements were collected (10 sites x 10 plots/site =100 plots)
  3. canopy.open: percent open sky from hemispherical photographs analyzed with Gap Light Analyzer (unit: dimensionless / missing value: NA)
  4. paper.loss: percent mass loss of cellose filter paper (2 sheets Whatman No. 1, ~ 3 g) after 20 weeks of incubation in the field (unit: dimensionless / missing value: NA)

hf082-03: soil properties

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: number of plot where measurements were collected (10 sites x 10 plots/site =100 plots)
  4. horizon: soil horizon
    • M: mineral soil
    • O: forest floor material excluding freshly fallen litter
  5. loi200: percent organic matter by weight, determined by 4 hours at 550C, with soil collected in the spring (200 series) (unit: dimensionless / missing value: NA)
  6. loi400: percent organic matter by weight, determined by 4 hours at 550C, with soil collected in the summer (400 series). Loss on ignition was not done on the fall (600 series) collection. (unit: dimensionless / missing value: NA)
  7. moisture200: gravimetric moisture of spring collection calculated as: (W-D)/D * 100 where W = mass of fresh soil sample, D= mass of soil sample dried at 105C for 48 h (unit: number / missing value: NA)
  8. moisture400: gravimetric moisture of summer collection (unit: number / missing value: NA)
  9. moisture600: gravimetric moisture of fall collection (unit: number / missing value: NA)
  10. core200: dry mass of soil spring collection core after passed through No.3 ½ sieve (unit: gram / missing value: NA)
  11. core400: dry mass of soil summer collection core after it passed through No.3 ½ sieve (unit: gram / missing value: NA)
  12. core600: dry mass of soil fall collection core after it passed through No.3 ½ sieve (unit: gram / missing value: NA)
  13. waterph: pH of soil in water (1 g mineral soil: 4 mL water; 1 g forest floor:10 mL water) (unit: number / missing value: NA)
  14. cacl2ph: pH of soil in 0.01 M CaCl2 (1 g mineral soil: 4 mL CaCl2; 1 g forest floor:10 mL CaCl2) (unit: number / missing value: NA)

hf082-04: resin bags

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: plot number. Each transect had 5-8 plot centers. Three additional bags per transect were installed between the plots.
  4. nh4: mg ammonium nitrogen per g resin (unit: milligramPerGram / missing value: NA)
  5. no3: mg nitrate nitrogen per g resin (mg g-1) (unit: milligramPerGram / missing value: NA)

hf082-05: nitrogen mineralization

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: number of plot where measurements were collected (10 sites x 10 plots/site =100 plots)
  4. horizon: soil horizon
    • m: mineral soil
    • o: forest floor material excluding freshly fallen litter
  5. sample: sample collected
    • 200NH4KG/HA: kg ha-1 ammonium nitrogen pool, spring collection
    • 400NH4KG/HA: kg ha-1 ammonium nitrogen pool, summer collection
    • 600NH4KG/HA: kg ha-1 ammonium nitrogen pool, fall collection
    • >200NO3KG/HA: kg ha-1 nitrate nitrogen pool, spring collection
    • 400NO3KG/HA: kg ha-1 nitrate nitrogen pool, summer collection
    • 600NO3KG/HA: kg ha-1 nitrate nitrogen pool, fall collection
    • 200NH4MG/KG: mg kg-1 ammonium nitrogen pool, spring collection
    • 400NH4MG/KG: mg kg -1 ammonium nitrogen pool, summer collection
    • 600NH4MG/KG: mg kg -1 ammonium nitrogen pool, fall collection
    • 200NO3MG/KG: mg kg -1 nitrate nitrogen pool, spring collection
    • 400NO3MG/KG: mg kg -1 nitrate nitrogen pool, summer collection
    • 600NO3MG/KG: mg kg -1 nitrate nitrogen pool, fall collection
    • 100NH4KG/HA: kg ha-1 ammonification, first 10-week incubation (May-July 2000)
    • 100NO3KG/HA: kg ha-1 nitrification, first 10-week incubation (May-July 2000
    • 300NH4KG/HA: kg ha-1 ammonification, second 10-week incubation (July-Oct 2000)
    • 300NO3KG/HA: kg ha-1 nitrification, second 10-week incubation (July-Oct 2000)
    • 100NH4MG/KG: mg kg -1 ammonification, first 10-week incubation (May-July 2000)
    • 100NO3MG/KG: mg kg -1 nitrification, first 10-week incubation (May-July 2000
    • 300NH4MG/KG: mg kg -1 ammonification, second 10-week incubation (July-Oct 2000)
    • 300NO3MG/KG: mg kg -1 nitrification, second 10-week incubation (July-Oct 2000)
  6. nmin: Nmin, measurement and units defined in "Sample" (unit: dimensionless / missing value: NA)

hf082-06: carbon and nitrogen

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. horizon: soil horizon
    • m: mineral soil below forest floor down to 15 cm (length of sample core)
    • o: forest floor excluding freshly fall leaves and twigs
  4. n: percent nitrogen by weight (unit: dimensionless / missing value: NA)
  5. c: percent carbon by weight (unit: dimensionless / missing value: NA)

hf082-07: lab decomposition

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. tray: tray code. The material was split in half into two identical trays.
  4. start: percent organic matter at the beginning of the experiment (unit: dimensionless / missing value: NA)
  5. week5: percent organic matter remaining after 5 weeks (unit: dimensionless / missing value: NA)
  6. week10: percent organic matter remaining after 10 weeks (unit: dimensionless / missing value: NA)
  7. week15: percent organic matter remaining after 15 weeks (unit: dimensionless / missing value: NA)
  8. week20: percent organic matter remaining after 20 weeks (unit: dimensionless / missing value: NA)
  9. week25: percent organic matter remaining after 25 weeks (unit: dimensionless / missing value: NA)
  10. week30: percent organic matter remaining after 30 weeks (unit: dimensionless / missing value: NA)

hf082-08: herb and shrub cover

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: plot number. Each transect had 5-8 plot centers
  4. sub: subplot code. Each plot had 3 randomly place subplots (A, B, C)
  5. cwd: percent cover of coarse woody debris (unit: dimensionless / missing value: NA)
  6. cwd.height: average height of CWD (unit: centimeter / missing value: NA)
  7. species: species code
  8. cover: percent cover of herbs and shrubs at each 1x1 m subplot to the nearest 1% (unit: dimensionless / missing value: NA)

hf082-09: seedling cover

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: plot number. Each transect had 5-8 plot centers
  4. sub: subplot code. Each plot had 3 randomly place subplots (A, B, C)
  5. species: species code
  6. cover: percent cover of seedlings for each 1x1 meter subplot. Individuals were considered seedlings if dbh was less than 1.5 cm. Individuals did not have to be growing in the subplot to be measured. (unit: dimensionless / missing value: NA)

hf082-10: seedling density

  1. site: site code (see site descriptions)
  2. treatment: treatment type where sample was taken
    • cut: cut forest
    • intact: intact forest
  3. plot: plot number. Each transect had 5-8 plot centers
  4. sub: subplot code. Each plot had 3 randomly place subplots (A, B, C)
  5. species: species code
  6. count: number of individuals growing in each 1x1 meter subplot. Individuals were considered seedlings if dbh was less than 1.5 cm (unit: number / missing value: NA)