- [Amphibian] |
- [Aquatic Macroinvertebrates] |
- [Bald Eagles] |
- [Freshwater Mollusks] |
- [Long-term Monitoring Plots] |
- [Mule Deer] |
- [Sage Sparrow Habitat] |
- [Small Mammals] |
- [Salmon] |
- [Steelhead] |
Ecological Monitoring on Long-Term Plots
Section 10.11.3)J. L. Downs,
M. A. Chamness,
C. A. Duberstein,
K. D. Hand, and
J. A. Stegen
Long-term monitoring plots, established as part of the Biological
Resources Management Plan (DOE/RL-96-32), are surveyed
periodically to determine the status of biological
populations and resources on the Hanford Site. Thirty original
plots, each with outside dimensions of 1 kilometer
(0.62 mile) by 200 meters (219 yards) were surveyed during
1996 to characterize vegetation and bird use. Since 1996,
five additional plots have been added to address particular
habitats such as riparian areas and abandoned fields. Surveys
have also been conducted on selected long-term monitoring
plots to provide data to evaluate changes in plant and animal
communities after fire and to measure the abundance and
diversity of small mammals in priority habitats. As part of
ongoing monitoring efforts, selected plots on the Hanford
Central Plateau were sampled during 2005 with four main
objectives: (1) evaluate habitat recovery after wildfire,
(2) evaluate bird use in burned and unburned habitats,
(3) evaluate the small mammal, reptile, and invertebrate
communities existing in burned and unburned communities
on the Central Plateau, and (4) concurrently measure
contaminants of interest in the small mammals, lizards,
invertebrates, and soil found in habitats adjacent to the
200 Areas. Data gathered to address the fourth objective
provide integrated information on the biological resources
and their potential exposure to Hanford-produced contaminants
at areas near existing Hanford cleanup operations.
These types of information are important supporting data for
the ongoing ecological risk assessments at Hanford.
10.11.3.1 Vegetation
J. L. Downs and
M. A. Chamness
[Top]
Vegetation canopy cover has been monitored on selected
long-term monitoring plots to evaluate the effects of the
24 Command Wildland Fire (DOE/RL-2000-63) in summer
2000 and assess vegetation recovery. Canopy cover of
herbaceous vegetation was measured on all plots in 1996.
Five plots that were burned in 2000 have been surveyed
periodically since the fire and were revisited in 2005 to evaluate
trends in recovery of the vegetation canopy cover.
One plot (plot 19) lying outside the burned areas was also
revisited in 2005 to evaluate canopy cover. Data were not
gathered on all plots during all years, but the canopy cover
means for the herbaceous plants on the burned plots are
presented here to demonstrate the trends in vegetation
recovery compared to the unburned plot. On each of the
plots, the canopy cover was measured in 20 quadrants along
each of three 100-meter (109-yard) transects spaced systematically
across the 20-hectare (50‑acre) plot. These data were
used to calculate an overall mean value for total herbaceous
canopy cover and the canopy cover of cheatgrass, an invasive
annual grass. Figure 10.11.7 indicates that the total
herbaceous canopy cover was less in 2005 on all the plots –
even the unburned plot had less herbaceous cover in 2005
than in 1996. The measured canopy cover of cheatgrass
was also found to be lower in 2005 on all plots surveyed.
However because the total herbaceous cover is less, cheatgrass
actually represents a larger proportion of the herbaceous
vegetation in the plots that were burned in 2000. It
is important to note that precipitation levels for the winter
months of 2004 (PNNL-15160) and 2005 were lower than
normal, thus moisture stored in the soil profile was less.
These conditions likely contributed to lower vegetation
cover measured in the spring of 2005. The data indicate
that overall the herbaceous cover on the burned plots has
not recovered to pre-burn levels. Cheatgrass canopy cover is
lower, but represents a greater proportion of the total herbaceous
vegetation.
10.11.3.2 Birds
C. A. Duberstein and
K. B. Larson
[Top]
Thirteen of the Biological Resources Management Plan
(DOE/RL-96-32) plots located within central Hanford were
revisited during 2005 to evaluate population trends and
provide information that could be used to support ongoing
risk assessments. These data are also important in evaluating
the response of the bird community after seven of the plots
were burned in 2000 during the 24 Command Wildland
Fire (Figure 10.11.8). Before the fire, 12 of these plots had
a sagebrush overstory and a bunchgrass understory, while
the other was dominated by grasses. The burned plots have
undergone natural vegetation recovery. The fire eliminated
most or all of the shrub overstory, resulting in plant communities
dominated by grass and forb species.
At each plot, at least three 10-minute point count surveys
were conducted during the spring (Bibby et al. 1992). The
total bird count for each plot was divided by the number of
surveys to standardize the data for comparisons.
A total of 1,952 individuals of 42 species were recorded. Western meadowlark (Sturnella neglecta) was the most abundant and most frequently observed species, being observed in 89% of all surveys. Sage sparrows and horned larks (Eremophila alpestris) were also frequently observed, and together these three species accounted for nearly 70% of all birds observed. None of the species observed were listed as threatened or endangered by either the Washington Department of Fish and Wildlife or the federal government. However, the loggerhead shrike (Lanius ludovicianus), merlin (Falco columbarius), and sage sparrow were observed birds that are classified as Washington State Candidate species by the Washington Department of Fish and Wildlife, and the shrike is also a federal species of concern.
Comparison of the abundances of the 12 most numerous species found in 2005 (post-fire) to abundances recorded prior to the 2000 wildfire showed decreases for only two species: white crowned sparrow (Zonotrichia leucophrys) and sage sparrow (Figure 10.11.9). The abundances of two species, loggerhead shrike and horned lark, increased slightly in 2005 compared to pre-fire estimates. For the lark sparrow (Chondestes grammacus), long-billed curlew (Numenius americanus), brown-headed cowbird (Molothrus ater), common raven (Corvus corax), savannah sparrow (Passerculus sandwichensis), and western meadowlark, there were no changes in abundance. None of the changes in abundance was statistically significant (α > 0.05).
Some of the temporal trends in bird abundance detected on the plots were observed elsewhere in the region (cowbird, meadowlark), while others were different than the observed regional trends (horned lark, shrike) (Table 10.11.3). Since most of the birds that breed within Hanford shrub-steppe habitats are migratory and only spend the breeding season in Washington State, it is difficult to determine what factors may be contributing to changes in populations and how much influence any one factor may have.
10.11.3.3 Small Mammals, Reptiles, and Invertebrates
K. D. Hand,
J. A. Stegen, and
R. E. Durham
[Top]
Three long term monitoring plots (Figure
10.11.8; plots 6, 10, and 19) located on the Hanford
Central Plateau were surveyed in May 2005 to estimate
small mammal, invertebrate, and lizard species richness
and to document the presence/absence of species that are
federally or state protected and/or sensitive. Plots 6 and 10
were selected for monitoring based on their location on the
200 Area plateau and because these plots were burned in
the 24 Command Wildland Fire in June 2000. Plot 19 is
located northwest of the 200-West Area and was not burned
in the 2000 fire. The plots within the fire footprint are
currently classed as bunchgrass mosaic vegetation cover and
have sparse patches of young shrubs scattered through the
plots. Vegetation found on monitoring plot 19 is a big sagebrush
– spiny hopsage/bunchgrass mosaic.
Live-trapping was used to sample the small mammals, reptiles, and invertebrates on the plots. One hundred and forty-seven Sherman live traps and 36 pitfall traps were placed on each plot and sampled over a 4-night period. The Sherman traps were used to capture small mammals, while pitfall traps captured lizards and invertebrates.
Four small mammal species were captured on all three plots: the northern grasshopper mouse (Onychomys leucogaster), white-footed deer mouse (Peromyscus maniculatus), Great Basin pocket mouse (Perognathus parvus), and Townsend’s ground squirrel (Spermophilus townsendii). Mammalian species richness was greatest at plot 6 with four species, plot 10 had the next greatest with three, and plot 19 had the lowest species richness with two species found (Table 10.11.4). Reptilian species richness was also greatest at plot 6 (four species), followed by plot 10 (two species) then plot 19 (zero species) (Table 10.11.5). However, the two snakes captured are considered incidental because the trapping methods were not considered suitable for capturing snakes. The invertebrate species’ richness (Table 10.11.6) did not follow the trend seen for small mammals and reptiles, plot 19 had the greatest number of species with 26, followed by plot 10 with 18 species, and plot 6 with 17 species.
The relative abundance and species richness of small mammals
in 2005 were compared to similar data collected on
these monitoring plots in 1998 before the 2000 24 Command
Wildland Fire. In all three plots, the relative abundance
of small mammals was higher in 2005 after the fire
than in 1998 (Figures 10.11.10 through 10.11.12). Species
richness was also higher on the two burned plots (plots 6 and
10) in 2005 compared to 1998. Two additional species were
found in 2005 on the burned plots compared to no change on
the unburned plot. Changes in species abundance and composition
may be related to differences in the amount of
ground litter and the vegetative community after a fire
(http://www.npwrc.usgs.gov/resource/habitat/fire/smmammal.htm).
Two Washington State Species of Concern candidate species and one monitor species were encountered during this effort. The Townsend’s ground squirrel, a state candidate species as of July 1, 2005, was present on plot 6. The sagebrush lizard, a state candidate species as of July 1, 2005, was present on plot 6. The northern grasshopper mouse, a state monitor species as of July 1, 2005, was present on plots 6 and 10.