This project is being accomplished with principal investigator
Dr. Eric Jokela in the School of Forest Resources and Conservation,
Drs. N. Comerford and. Sabine Grunwald in our department and
Dr. Ed Barnard of the State Division of Forestry, who is also
funding the work. Drs. Chris Bliss and I. Lopez-Zamora where
the post-docs from our program working on the project.
Recent observations in north Florida have hinted that the presence
of poultry houses is promoting the incidence and expression
of a fungal disease of slash pine (Pinus elliotti var. elliotti
Engl.) known as pitch canker (Fusarium circinatum). Poultry
operations emit high levels of N and recent intensification
in the number of poultry houses per farm and the conversion
from passive (screen) to tunnel ventilation (fans) have concentrated
poultry house N emissions.
Earlier investigations showed that high N additions to slash
pine stands can increase the expression of pitch canker, which
is endemic to the region. However, pitch canker can escalate
when N loading is high. Disease progression causes tree mortality
and reduced stand volume growth, particularly in stands 10 years
and older.
The spatial impact of poultry houses on pine N status and, particularly,
its correlation to pitch canker is not well documented for the
poultry-growing region of north Florida. Therefore, the objective
of this study was to:
(1) investigate the spatial distribution of the impact of a
system of poultry houses on the N status of an adjacent 15-yr
old slash pine stand,
(2) determine the spatial distribution of pitch canker and
tree volume growth in the same stand,
(3) determine the spatial correlation between N status of the
pine plantation and the incidence and expression of pitch canker,
and
(4) determine which N metrics are most useful for relating
N and pitch canker in future studies or monitoring programs.
Our preliminary conclusions from this study are that spatial
patterns of N content of throughfall and of forest floor and
foliage N concentration in a slash stand adjacent to poultry
houses were a result of the N emissions from the poultry houses.
Foliage and forest floor N concentrations are among the highest
recorded values for this species and represent a very high loading
of parts of this stand with N. The N status of the stand was
most easily and efficiently measured using the forest floor
as the metric. High pitch canker incidence and severity were
coincident with high levels of stand N and with close proximity
to the poultry houses. The poultry houses loaded the adjacent
forest stand with N which predisposed trees closest to the houses
to higher incidence and severity of pitch canker. The enhanced
mortality associated with pitch canker overcame any potential
productivity benefit that might accrue from the increased N
additions. Both foliar N and forest floor N appeared to be useful
metrics for monitoring the N loading and potential for pitch
canker infection. These results are for a slash pine stand that
has not yet shown the high infection rate seen in other areas
that have larger numbers of poultry houses per farm and for
longer periods of time. Windbreaks should be considered as a
preventative measure in similar situations.
The following figures illustrate the spatial patterns of N
in the foliage and pitch canker.
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