Dr.
Porneluzi's Research
Dr.
Porneluzi's Research
My research generally deals with the effect of
the composition of the landscape on a region's ecology. I focus on how the
landscape affects birds that require forests for their breeding grounds. Much of
my work is conducted in the Ozark forests in south-central Missouri.
My most recent work is in association with the
Missouri
Ozark Forest Ecosystem Project (MOFEP).
This is a multi-year, multi-investigator experiment designed to measure the
effects of two types of forestry management on components of the ecosystem,
including breeding birds. The goal of the study is to evaluate the impacts of
even-aged (clear-cutting) versus uneven-aged (select cutting) harvesting
techniques on a landscape scale over a 150 year rotation.
The study includes 9 large (>250 ha) study sites. We studied these
sites from 1991 to 1995. Then, in 1996, portions of three of the sites were
subjected to even-aged management, three sites received uneven-aged management
and the remaining three sites served as controls and received no harvest
management.
This research would not be possible without
the help of over 200 hard-working, hard-playing interns that we have worked with
over the years. Approximately 27 interns are hired each summer to conduct the
field work as well as their own independent study project. Interns map the
locations of breeding bird territories; search for and monitor nests; and
capture birds in mist-nets for banding.
Among
five forest breeding focal species, we found significant changes in density for
three. Ovenbird density declined more with even-aged and uneven-aged management
than on control sites two years post-treatment. Wood Thrush density increased
with even-aged management relative to control sites two and three years
post-treatment. Kentucky Warbler density increased with both treatments relative
to control sites following timber harvest.
Many species require the regenerating vegetation that grows after trees
are cut. Three of six early successional focal species showed significant
increases in density. Indigo Bunting increased with both types of management all
three years following treatment. Yellow-breasted Chat density increased with
even-aged management all three years and with uneven-aged management three years
post-treatment relative to control sites. Prairie Warbler density increased with
even-aged management one and two years after harvest. Hooded Warblers increased
in abundance with both treatments following harvest, but their relatively low
densities were not statistically significant.
We might have expected nest success to decline after timber harvesting
because many species that are known to prey on bird's nests appear to be more
abundant in landscapes that have a greater variety of habitat types. Also,
Brown-headed Cowbirds tend to be more abundant where there is more open habitat
and female cowbirds remove eggs from nests and replace them with their own eggs
(brood parasitism).
However, the daily survival rate of nests was over 95% and did not
change significantly after timber harvesting. The average success rate of nests
was about 29%. The rates of brood parasitism by Brown-headed Cowbirds was a
relatively low 10% and also did not change following timber harvesting.
It appears that as long as the region remains
predominantly forested, timber harvest does not lead to an increase in the
populations of nest predators, at least over the short-term. This may change
over time and with additional timber harvests at the next round of cutting.
Brown-headed Cowbird populations appear to be limited by the amount of feeding
habitat in the region. Cowbirds require short grass and pasture with large
grazing animals and if the amount of this habitat remains the same, the cowbird
population will probably remain stable.
The responses of the songbirds were variable.
Among the forest breeding species, two showed no change in abundance, one
declined with even-aged management in some years and two increased in abundance
when forest openings were created. Among the early-successional species, several
showed highest abundance on the sites that were subjected to even-aged
management. No species has shown a clear preference for uneven-aged managed
sites.
If the same amount of timber is removed,
even-aged management results in a small number of relatively larger openings
(clear-cuts) whereas uneven-aged management results in a large number of smaller
openings spread over a larger area. Therefore, un-evenaged management tends to
disrupt the habitat of a greater number of forest breeding bird territories and
does not benefit some early-succession species. In the Ozark region, small
clearcuts, (<12 ha.) applied on a sustainable rotation may be less
detrimental for forest birds and lead to the greatest diversity of early-successional
bird species.
It is important to keep in mind that other
components of the ecosystem may be impacted differently.