for plant plot analysis:
Mexico Hantavirus Survey
purposes, the species-specific percentage cover of plants, coupled with
some measures of seed productivity, will be sufficient to discern
temporal and spatial differences in plant food resource abundances. To
1. Establish a
total of 16 one-square meter quadrats in association with each trapping
web (or grid). With generally 2-3 replicate webs per site, this would
create 32-48 samples for vegetation. The plant quadrats can be
establishedin clusters of four quadrats/cluster, arranged in a square,
with 10 meter intervals between quadrats. Each of the four clusters
(with 4 quads each) should be located at least 20 meters outside the
web perimeter to avoid trampling by rodent trapping crews. We would
suggest orienting the 4 clusters of quadrats in a standard fashion,
such that clusters occur 20 meters outside of traps numbers 12, 48, 84,
and 120 (cardinal directions from the center of each web).
2. Each quadrat
should be permanently marked with rebar in at least two (opposite)
corners, so that the sampling frame (described below) can be relocated
exactly each time the quad is sampled. Quadrats should be numbered with
permanently attached metal tags so that data from various sample
periods refers to the same quadrat.
should be measured with a 1 x 1 meter PVC-pipe frame, with strings
criss-crossing the frame at 10 cm increments. This will create a
100-grid square frame, making it very easy to determine percentage
cover of plants.
4. To sample the
plants on the quadrat, place the frame on the plot, but taking care not
to crush the vegetation. For some taller vegetation types, it may be
necessary to build the frame with PVC "legs" (like a small table) that
would keep it above the ground and not press or damage the plants. When
the frame is in place, the observer looks straight down on it, and
estimates the amount of cover for each species of plant present; this
is done by counting the number of 10x10 cm squares with a particular
species of plant in them. Partial squares can be tallied as well, if
the plant does not cover the entire square. Each full 10x10 cm square
equals 1% cover of the entire quadrat.
quadrats of this size usually have fewer than 10 plant species, and
thus the data collection of the plants takes on the order of 4-6
minutes per quadrat; there will likely be some slower times at first,
until the field crews learn the identifications of the common plants.
The entire plant data collection on up to 48 quadrats could be done by
a team of two people in 2 days utilizing the "middle" part of each day
(assuming rodent trapping in the mornings and rebaiting in the late
5. We suggest
sampling plants two times per year; once in the early part of the
summer (to estimate the cover of spring plants), and once late in the
summer to get the full summer's production.
production: At the time that plants are being sampled, estimates of
seed abundances can be made. These can be more qualitative than
quantitative; i.e., seed numbers per plant of each species can be
measured as: NONE PRESENT
1-10 SEEDS OBSERVED PER
10-50 SEEDS OBSERVED PER
50-100 SEEDS OBSERVED
> 100 SEEDS OBSERVED
Such data will
likely be able to distinguish between drought years (practically no
seed production) and wet years (loads of seeds).
7. The data from
all of the quadrats can be averaged by species or pooled to get total
plant cover and seed production. We can develop a common data sheet if
everyone is interested in doing this (probably a good idea...)
8. Some estimate
of juniper berry, pine nut and acorn production should be undertaken in
the fall of each year for those sites that have such species. We are
currently working out a method to do this, and should be able to
provide you with protocols later this summer.
coverage should be subdivided into grasses, herbs, and shrubs, then
analyzed calculated for each site. Changes in cover can then be
calculated through time and correlated with rodent abundance changes.