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Harvard Forest Data Archive

HF099

Stream Periphyton Response to Hemlock Mortality in Central Massachusetts 2006

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Data

Overview

  • Lead: William Sobczak
  • Investigators: Timothy Rowell
  • Contact: William Sobczak
  • Start date: 2006
  • End date: 2006
  • Status: completed
  • Location: Central Massachusetts
  • Latitude: +42.0 to +42.7
  • Longitude: -72.8 to -71.8
  • Elevation:
  • Taxa:
  • Release date: 2009
  • Revisions:
  • EML file: knb-lter-hfr.99.12
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: regional studies; watershed ecology
  • LTER core area: disturbance
  • Keywords: hemlock, hemlock woolly adelgid, periphyton, photosynthetically active radiation, stream ecology
  • Abstract:

    The Hemlock Wooly Adelgid (HWA) invasion is expected to cause widespread mortality of eastern hemlock [Tsuga canadensis (L.) Carriere] throughout much of New England. Light levels in streams with hemlock riparian zones are anticipated to increase as hemlock are replaced by deciduous trees. We sought to: 1) quantify differences in light reaching streams with hemlock and deciduous riparian zones, 2) determine if increases in light result in higher periphyton biomass, and 3) explore the role of macroinvertebrate grazing on periphyton biomass as light increases in an attempt to help predict stream ecosystem responses to hemlock mortality. Light measurements were taken along 100-800m stream reaches with riparian zones of healthy hemlock and deciduous trees in MA and CT in order to document an integrated light profile for each stream. In addition, a 2 x 2 factorial experimental design with five replicates was executed on a deciduous reach of Egypt Brook in central MA, in which light (high light vs. low light) and grazing (high grazing vs. low grazing) were manipulated. Light measurements were significantly higher for streams with deciduous riparian zones than hemlock riparian zones. Controlled shading reduced chlorophyll a, while excluding grazing yielded inconclusive results. Periphyton biomass in Egypt Brook was found to be light limited, and grazing did not suppress periphyton biomass. As hemlocks die, in-stream light will be significantly augmented, and periphyton biomass will increase. A challenge for stream ecologists will be to incorporate multiple physical, chemical, and biological controls on biota in order to fully understand how regional hemlock mortality will alter stream periphyton biomass.

  • Methods:

    Stream survey

    Examination of topographic maps and aerial photos located potential streams with hemlock and deciduous riparian zones in Massachusetts and Connecticut. The streams were visited and assessed to determine if study qualifications were met. Streams studied had to be low order streams and have riparian zones dominated by either hemlock trees or deciduous trees. During July and August 2006 PAR (irradiance) measurements were taken at the selected streams on sunny days between 11:00am and 1:00pm. PAR measurements were taken over the stream every 10 meters along the reach using the AccuPar Linear PAR/LAI Ceptometer Model PAR 80. All the PAR measurements for each stream were averaged to find a mean PAR value for each stream.

    Shading experiment design

    A block design (5 replicate blocks), with a 2 X 2 factorial design (20 containers total) in which light (ambient high light vs. low light) and grazing (ambient high grazing vs. low grazing) were manipulated, was setup on the deciduous reach of Egypt Brook. Twenty plastic food storage containers (18.0cm x 18.0cm x 5.5cm), four per block, were used as the experimental units. Briefly, the inside bottoms of the containers were sanded and four unglazed ceramic tiles (4.80cm x 4.80cm) were attached with aquarium silicone sealant. Each block contained four containers with four different experimental treatments: (1) ambient high light, ambient high grazing pressure; (2) ambient high light, low grazing pressure; (3) low light, ambient high grazing pressure; and (4) low light, low grazing pressure. The five blocks provided five replicates for each experimental treatment.

  • 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:

    Sobczak W. 2009. Stream Periphyton Response to Hemlock Mortality in Central Massachusetts 2006. Harvard Forest Data Archive: HF099.

Detailed Metadata

hf099-01: chlorophyll a

  1. block: block number
  2. light: light treatment
    • HL: high light
    • LL: low light
  3. grazing: grazing treatment
    • HG: high grazing
    • LG: low grazing
  4. chl.a: mean Chorophyll A (unit: microgramPerCentimeterSquared / missing value: NA)

hf099-02: PAR

  1. date: date
  2. stream: stream name
  3. mean.par: mean PAR (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  4. median.par: median PAR (unit: micromolePerMeterSquaredPerSecond / missing value: NA)