You are here

Harvard Forest Data Archive

HF344

Leaf and Soil Nitrogen Following Gypsy Moth Defoliation in Central Massachusetts 2018-2019

Related Publications

Data

Overview

  • Lead: Emma Conrad-Rooney, Audrey Barker Plotkin, Jaclyn Hatala Matthes
  • Investigators: Joseph Elkinton, Valerie Pasquarella
  • Contact: Information Manager
  • Start date: 2018
  • End date: 2019
  • Status: completed
  • Location: Central Massachusetts
  • Latitude: 42.5313 to 42.3144
  • Longitude: -72.5308 to -72.1676
  • Elevation: 90 to 160 meter
  • Taxa: Lymantria dispar (gypsy moth), Quercus rubra (red oak)
  • Release date: 2020
  • Revisions:
  • EML file: knb-lter-hfr.344.1
  • DOI: digital object identifier
  • EDI: data package
  • DataONE: data package
  • Related links:
  • Study type: short-term measurement
  • Research topic: invasive plants, pests and pathogens; soil carbon and nitrogen dynamics
  • LTER core area: organic matter, inorganic nutrients, disturbance
  • Keywords: defoliation, leaves, nitrogen, oak, soil chemistry
  • Abstract:

    In this study we investigated relationships between ecosystem nitrogen (N) cycling and tree defoliation during a recent 2015-2018 irruption of invasive gypsy moth caterpillars (Lymantria dispar), which can cause tree stress and sometimes mortality following multiple years of defoliation. Nitrogen is a critical nutrient that limits the growth of caterpillars and plants in temperate forests. We assessed the associations between N concentrations, soil solution inorganic N availability, and defoliation intensity by L. dispar at the scale of individual trees in the Amherst, MA area and forest plots in the Quabbin Reservoir area.

  • Methods:

    Measurements at Individual Trees

    We measured leaf and soil N concentrations at 12 individual Quercus rubra trees in the Amherst, MA area. Each tree was scored for overall visual defoliation in the field in October 2018. Herbivory measurements were also scored on 30 leaves collected from each tree within reach from the ground in October 2018, and these leaves from each tree were pooled and analyzed for leaf N concentration. Soil samples of the O-horizon were collected in three locations about 0.5 m away from each tree and up to 10 cm depth using a 5 cm diameter split PVC corer and a mallet. These soil samples were pooled for each tree and analyzed for soil N concentration.

    Measurements at Forest Plots

    We also collected data at nine 90 x 90 m plots in Central MA, where each plot was subdivided into three 20 x 20 meter subplots. Within each 20 x 20 m subplot, four soil samples of the O-horizon were collected 5 m inward towards the center of the subplot from each of the four plot corners. The samples from each subplot were then homogenized into a composite sample and analyzed for percent nitrogen.

    At each plot we used data from a Landsat-derived forest condition assessment product (doi:10.5281/zenodo.1493407) to calculated plot-level cumulative defoliation. Using this data product we calculated the cumulative seasonal defoliation by calculating the mean annual values in a 45 m radius circle from each plot center and adding values from 2015, 2016, 2017, and 2018. We also used a categorical version of the Landsat-derived data product to classify each plot as defoliated or not in the 2015-2018 growing seasons. Plots were classified as defoliated in each year if the mean categorical value for defoliation was “moderate” or higher.

    Within each plot we measured the availability of inorganic N in soil solution during the growing season using resin bags buried beneath the soil. For each resin bag, 10 g of resin was added to a mesh stocking packet and buried 5-10 cm below the soil surface in the center of the first subplot within each larger plot on June 11-14, 2019. Each resin bag was collected after 75-78 days to quantify accumulation of soil solution inorganic N over this period. Nitrate (NO3-) and ammonium (NH4+) were extracted from the resin using 2M KCl and we measured the resulting KCl extracts for NO3- and NH4+ concentrations using colorimetric analysis. Each sample was run twice for replication and quality assurance. The resulting concentrations of NO3- and NH4+ in ppm were converted to mg per kg dry resin, the two replicates were averaged, and that value was divided by the number of days that the resin bag was deployed in order to get the average rates of NO3- and NH4+ availability in mg per kg dry resin per day. To calculate the total rate of inorganic N availability, we added the mean rates of NO3- and NH4+ for each resin bag.

  • 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:

    Conrad-Rooney E, Barker Plotkin A, Hatala Matthes J. 2020. Leaf and Soil Nitrogen Following Gypsy Moth Defoliation in Central Massachusetts 2018-2019. Harvard Forest Data Archive: HF344.

Detailed Metadata

hf344-01: leaf and soil nitrogen at individual trees

  1. tree.id: tree identification code
  2. species: tree species
  3. tree.defol.field: visual estimate of whole-tree defoliation on a scale of 0-100% in October 2018 (unit: dimensionless / missing value: NA)
  4. leaf.herbiv.avg: average estimate of 30 individual leaves scored for herbivory on a scale of 0-100% collected in October 2018 (unit: dimensionless / missing value: NA)
  5. leaf.n.percent: percent nitrogen content by mass from a composite sample of the 30 individual leaves from each tree (unit: dimensionless / missing value: NA)
  6. leaf.c.percent: percent carbon content by mass from a composite sample of the 30 individual leaves from each tree (unit: dimensionless / missing value: NA)
  7. soil.n.percent: percent nitrogen content by mass from a composite sample of 3 soil cores collected of the organic horizon around each tree in July 2019 (unit: dimensionless / missing value: NA)
  8. soil.c.percent: percent carbon content by mass from a composite sample of 3 soil cores collected of the organic horizon around each tree in July 2019 (unit: dimensionless / missing value: NA)
  9. leaf.c.n: ratio of leaf.c.percent to leaf.n.percent for each tree (unit: dimensionless / missing value: NA)
  10. soil.c.n: ratio of leaf.c.percent to leaf.n.percent for each tree (unit: dimensionless / missing value: NA)

hf344-02: soil nitrogen at forest plots

  1. plot: unique plot identification code
  2. defol.cumulative: cumulative 2015-2018 growing season defoliation severity from Landsat-based forest condition assessment data product (unit: dimensionless / missing value: NA)
  3. defol.freq: number of years the plot experienced “moderate” or higher defoliation severity in the 2015-2018 time period (unit: number / missing value: NA)
  4. oak.count: oak count (unit: number / missing value: NA)
  5. soil.n.percent: percent nitrogen content by mass from a composite sample of 3 subplots with 4 soil cores collected of the organic horizon in July 2019 (unit: dimensionless / missing value: NA)
  6. soil.c.n: soil carbon-to-nitrogen ratio by mass from a composite sample of 3 subplots with 4 soil cores collected of the organic horizon in July 2019 (unit: dimensionless / missing value: NA)
  7. n.mg.kg.day: rate of nitrate accumulation in soil solution over 75-78 days (June to August 2019) in mg-N per kg resin per day (unit: milligramPerKilogramPerDay / missing value: NA)
  8. ammon.mg.kg.day: rate of ammonium accumulation in soil solution over 75-78 days (June to August 2019) in mg-N per kg resin per day (unit: milligramPerKilogramPerDay / missing value: NA)
  9. n.min.mg.kg.day: rate of mineral N accumulation in soil solution over 75-78 days (June to August 2019) as the sum of ammon.mg.kg.day and n..mg.kg.day (unit: milligramPerKilogramPerDay / missing value: NA)