A study of the effects of canopy coverage on the abundance of herbaceous plant species in Danby Woodlot at York University

Hypothesis

Taller
plant species with higher canopy coverage outcompete shorter plant species due
to interference competition for sunlight. Therefore, in areas with a high canopy
coverage, there will be a lower abundance of herbaceous plant species.

Predictions:

1.     The higher the canopy coverage, the lower
the abundance of herbaceous exotic plant species and herbaceous native plant species.

2.     The higher the canopy coverage, the lower
the ground coverage.

Study-Site description

Data was collected at the Dandy Woods on York University’s Keele
campus. This was a woodlot (forested area), containing primarily deciduous
trees, with no water source. The area was rectangular in shape and was
approximately 250000m2. It was bordered by Chimneystack Road to the
north, Keele Street to the east, grassland to the south, and the Chimneystack
Lot to the west. GPS coordinates for the woodlot was 43.768756, -79.5079.
Elevation for the woodlot was 126.30201 m. The weather was mostly rainy with
temperatures reaching 12C and humidity reaching 88% and wind speeds of 23km/h.

Meta-Data

Data was collected from a woodlot (43.768756, -79.5079) at York University’s
Keele campus. Data was collected via visual survey using transects (two 30m
transects), pan traps, 1mx1m quadrats, sweep nets and point survey techniques.
For the first data set we obtained the abundance of native plants, abundance of
exotic plants, and total number of flowers via quadrat sampling
(n=25) along a 50m transect (east to west). Every two metres a quadrat was
placed on alternating sides of the transect. The number of individuals of herbaceous
native and exotic plant species were counted within the quadrat. Grass species
were considered to be exotic and all other plants were considered native. Next,
the total number of observed flowers within the quadrat were counted; all
levels of inflorescence (i.e. buds and blossoming) were considered flowers.

For the second dataset a 50m transect was drawn (east to west) and
the measured variables were abundance of woody plants, canopy cover, ground
cover, and total number of flowers. Abundance of woody plants were counted
every 2m within 0.5m of the transect. Only plants larger than 1.5m in height
were counted. Having a height requirement decreased the probability of counting
a non-woody plant. Also, every two metres, the ground cover and canopy cover
was approximated in percent by visually dividing the ground and canopy space
into quadrats, then the area covered was estimated by the surveyor as a
percentage of the total space. Total number of flowers were counted within 0.5m
of the transect on both sides every 2m (n=25).

For the third dataset, abundance of vertebrates, diversity of
vertebrates, abundance of invertebrates observed and abundance of humans were
measured. A 50 m transect was drawn (east to west) and point surveys were
conducted via visual inspection of the area within a 50m radius of the start
point of the transect. The total number of vertebrates, diversity of
vertebrates and abundance of humans was observed for a 15-minute period (n=2).
Then in 15 minutes, all humans not part of the study group were counted to
survey pedestrian circulation. Following, the abundance of invertebrates was
counted (i.e. insects, mollusks, etc.) within a 5.0m radius of the start of the
transect for 15 minutes (n=2).

For the fourth dataset (measuring abundance of invertebrates in
pan traps and abundance of invertebrates caught in sweep nets), 6 pan traps
(blue, white, yellow) were placed 3 meters apart along a 50m transect while
alternating colors. The pan trap was left for 45 minutes and then the number of
invertebrates caught were counted (n=6). Then, along the 50m transect, sweep
nets were used to catch any invertebrates (flying and ground-dwelling). The
nets were swept upwards from a left to right motion low to the ground (n=10).

Methods:

50m transects (combining two 30m transects) were run (east to
west) in the woodlot; quadrat samples were taken on both sides of the transect
every 2m (n=25). To count the abundance of native and exotic herbaceous plants,
surveyors used a 1.00m x 1.00m quadrat to visually inspect and sample
individuals. Sampling was conducted by the surveyor counting the abundance of
native and exotic herbaceous plants per the bottom-left quarter of the quadrat,
the sampling was then multiplied by a factor of 4 to gain total abundance.
Total number of flowers were counted and inspected by the surveyor
(inflorescences were counted as individual flower units).

For woody plants, a 50m transect was run (east to west) and for
every 2m a surveyor observed for woody plants (defined as plants with a height
greater than or equal to 1.5m) within 0.5m of the transect (n=25). At these
points, canopy and ground coverage was estimated via surveyor’s visual
inspection, by visualizing quadrats above and below the surveyor. As well,
total flower numbers were recorded similarly within the 0.5m area (from the
transect) as described above.

Point surveys were conducted for periods of 15 minutes (n = 2) for
the abundance of vertebrates, diversity of vertebrates, abundance of
invertebrates, and abundance of humans. The survey involved running a transect
for 50m and a surveyor visually inspecting and counting for the abundance of
vertebrates, diversity of vertebrates and abundance of humans within a 50m
radius of the transect start point. Diversity of species was determined via
visual inspection. Within a 5m radius of the transect start point abundance of
invertebrates was measured.

Pan traps were set 3m apart while alternating colours (yellow,
blue, white) along the length of a transect (50m). Each pan trap was one
replicate (n=6) and the total number of invertebrates within the pan trap were
counted and recorded. Then, sweep nets were conducted next to the 50m transect.
Each sweep was one replicate (n=10) and the total number of invertebrates found
at the end of the sweep were counted and recorded.

Variable Definitions

Abundance of native plants – The visual inspection and count of
native plant species (primarily flowering species) per a 1.0m x 1.0m quadrat.
Numerical, discrete.

Abundance of exotic plants – The visual inspection and count of
exotic plant species (primarily grass species) per a 1.0m x 1.0m quadrat.
Numerical, discrete.

Total number of flowers (quadrat) – The visual inspection and
count of flowers (inflorescences were counted as single units) per a 1.0m x
1.0m quadrat. Numerical, discrete.

Abundance of woody plants – The visual inspection and count of
woody plants (taller than 1.5m). Numerical, discrete.

Canopy cover – The visual estimation of the percent area covered
by the canopy of the woody plants. Numerical, continuous.

Ground cover - The visual estimation of the percent area covered
by the herbaceous plants on the ground. Numerical, continuous.

Total number of flowers (transect)– The visual inspection and
count of flowers within 0.5m of the transect on both sides. Numerical,
discrete.

Abundance of vertebrates – The visual inspection and count of
vertebrate species in the radius of the point survey. Numerical, discrete.

Vertebrate species – The visual inspection and count of the
diversity of vertebrate species within the radius of the point survey.
Numerical, discrete.

Abundance of invertebrates – The visual inspection and count of
invertebrate species in the radius of the point survey. Numerical, discrete.

Abundance of invertebrates pan traps – The visual inspection and
count of invertebrates caught in pan traps during a 45 minute period.
Numerical, discrete.

Abundance of invertebrates sweeps – The visual inspection and
count of invertebrates caught in sweep nets over a 50m transect. Numerical,
discrete.

Habitat – The study site area which includes: forest,
grassland, disturbed area, impermeable surface, or near pond. Categorical,
nominal.