Long-term trends in abundance of Lepidoptera larvae in northern hardwoods forests

TITLE
Long-term trends in abundance of Lepidoptera larvae in northern
hardwoods forests

PRINCIPAL INVESTIGATOR
Richard T. Holmes
Dartmouth College

BEGIN DATE
1986

END DATE
1997

LOCATION
BIRD AREA at HBEF, plus 3 other sites in WMNF

LOCATION DESCRIPTION
HBEF data were obtained in the 10-ha bird study plot, adjacent to (south/southwest) Wier 6. Other 3 "replicate" sites located outside HBEF, but in White Mountain National Forest at same elevations and aspects and in stands with similar forest history and vegetation. See site descriptions below.

DATA DESCRIPTION
Numbers and lengths of Lepidoptera Larvae (caterpillars, all species) censused on shrub level foliage at biweekly intervals from late May/early June through late July/early August each year. Samples taken at HBEF from 1986-1997 on American Beech and Sugar Maple in all years, plus Hobblebush and Striped Maple in 1996 and 1997. Other plots sampled from 1986-1995 on American Beech and Sugar Maple only. Data on numbers and lengths converted to dry weight biomass per 50-leaf unit, using length-weight regression (see "Calculations" below).

SAMPLING DESIGN (Design and method of collecting data)
Visual censuses of larvae on two 50-leaf samples at each of 40 grid intersection points, located at 50 m intervals, on each tree species (American beech and sugar maple in all years, hobblebush and striped maple in 1996 and 1997 on HBEF plot only). Thus, 4000 leaves of each tree species were searched at 2-week intervals at each site from late May to late July/early August (4-6 sampling periods each year).

SITE DESCRIPTIONS
      SITE: "Hubbard Brook"
      OWNER: National Forest
      CHARACTERISTICS:
      GEOGRAPHIC LOCATION: HBEF, Bird Area, adjacent to lower third of watershed 6.
      VEGETATION: Northern hardwoods forest (beech, sugar maple, yellow birch)
      HISTORY: Selectively logged in early 1900s. Forests approximately 75-90 years of age at time
of sampling.

      SITE: "Moosilauke"
      OWNER: National Forest
      CHARACTERISTICS:
      GEOGRAPHIC LOCATION: 8 km north of HBEF. Plot located 100 m NW of NH route
118, 8 km west of North Woodstock, NH (in township of Woodstock, NH)
      VEGETATION: Northern hardwoods forest (beech, sugar maple, yellow birch)
      HISTORY: Selectively logged in early 1900s. Forests approximately 75-90 years of age at time
of sampling.

      SITE: "Russell Pond"
      OWNER: National Forest
      CHARACTERISTICS:
      GEOGRAPHIC LOCATION: 11 km NE of HBEF. Plot located 1.2 km SW of Russell Pond,
Thornton, NH.
      VEGETATION: Northern hardwoods forest (beech, sugar maple, yellow birch)
      HISTORY: Selectively logged in early 1900s. Forests approximately 75-90 years of age at time
of sampling.

      SITE:"Stinson Mountain"
      OWNER: National Foest
      CHARACTERISTICS:
      GEOGRAPHIC LOCATION: 13 km SW of HBEF. Plot located 1.7 km E of Stinson
Mountain lookout tower, Rumney, NH
      VEGETATION: Northern hardwoods forest (beech, sugar maple, yellow birch)
      HISTORY: Selectively logged in early 1900s. Forests approximately 75-90 years of age at time
of sampling.

CALCULATIONS
Caterpillar biomass determined from a length-weight (dry) regression (J.C. Schultz and R.T. Holmes, unpubl. data; see Rodenhouse 1986, Ph.D. Thesis, Dartmouth College, Hanover, NH). Lengths were measured on animals in situ in the field.

REFERENCES

Holmes, R.T., T.W. Sherry, and F.W. Sturges. 1986. Bird community dynamics in a temperate deciduous forest: long-term trends at Hubbard Brook. Ecological Monographs 56: 201-220.
Holmes, R.T., T.W. Sherry, and F.W. Sturges. 1991. Numerical and demographic responses of temperate forest birds to annual fluctuations in their food resources. Acta International Ornithological Congress 20: 1559-1567.
Holmes, R.T., and J.C. Schultz. 1988. Food availability for forest birds: effects of prey distribution and abundance on bird foraging. Canadian Journal of Zoology 66: 720-728.

ACCESS
Public

DATA LOCATION
Dartmouth College

LAST UPDATED
1997

CONTACT PERSON
      Richard T. Holmes
      Department of Biological Sciences
      Dartmouth College
      Hanover, NH 03755
      E-mail: richard.t.holmes@dartmouth.edu

VARIABLES
"Leps.txt" is a text file containing all the lep data for 1986 - 1997. The first row is the column labels. There are no zeros in the dataset (i.e. grid points where no leps were found are not included). Data from American Beech (Fagus grandifolia) and Sugar Maple (Acer saccharum) for all plots are given for the years 1986-1995. Only Hubbard Brook was censused for leps in 1996 and 1997, and in those two years, samples were also obtained from Striped maple (Acer pensylvanica) and Hobblebush (Viburnum alnifolium). Data are given for number, taxon (family level), and biomass conversion (in mg) for larvae found in each 50-leaf sampling unit.

Column	Variable	Description	Units	Coded	Missing Value
1	Date	Sample date	m/dd/yy	n	none
2	yearday	Day of year	-	n	none
3	Plot	Plot number	-	y	none
4	count	sample group per year	-	n	none
5	grid letter	grid letter	-	n	none
6	grid number	grid number	-	n	none
7	tree species	tree species	-	y	none
8	tree rep	replicate for tree	-	n	none
9	number lep	number of larvae per 50 leaf sample	-	n	none
10	lep species	lepidoptera taxa	-	y	none
11	lep length	total combined length of lepidoptera found on 50 leaf sample	mm	n	none
12	lep biomass	total biomass of lepidoptera found on 50 leaf sample	mg	n	none

CODES

      PLOT
Hubbard Brook = 1
Moosilauke = 2
Russell = 3
Stinson = 4

      TREE SPECIES
Beech = 1
Sugar maple = 2
Striped maple = 3
Viburnum = 4

      LEP TAXA (Family-level only)
Geometrid = 2
Noctuid = 3
Notodontid = 4
Pyraloid, Tortricoid, Coliophorid, Psychid = 5
Other species = 6

DATA FILE NAME(S)
leps.txt