The primary objective of
this study is to test whether increased nitrogen (N) fertility mitigates
ozone injury to ponderosa pine. The response of this common western
conifer to oxidant exposure has been well described and plant responses
to N fertility are generally understood, but the combined effects of
elevated N deposition and oxidant exposure have not been tested. Nitrogen
induced mitigation of foliar ozone injury will be evaluated by a multivariate
assessment of visible foliar injury and associated characteristics.
A collection of biochemical attributes which play a role in foliar carbon
acquisition (CO2 fixation) and export (via translocation),
and N metabolism and storage will be tested as indicators of changes
in forest health.
Ozone concentrations frequently
reach or exceed 100 ppb in mid-elevation forests in Sequoia/Kings Canyon
National Park, California. Nitrogen deposition, however, has been estimated
for only a few sites in the Sierra Nevada. Ozone and nitrogenous pollutants
are believed to be the major pollutant types in the west-side mid-elevation
forests of the Sierra Nevada and are usually co-occurring. Only one
study, to date, has addressed the combined effects of these co-occurring
pollutants on mature trees in situ. In that study two mid-elevation
mixed conifer sites in the San Bernardino Mountains with differing ozone
levels have been exposed to background N deposition, or fertilized with
50 or 150 kg ha-1 of slow release urea (USDA funding awarded
to Mark Ferm, Mark Poth, and Paul Miller; ongoing). The study proposed
here will replicate the San Bernardino work using background N deposition
levels and the lower fertilization treatment (+50 kg ha-1).
This will provide additional
information regarding the responses of a Sierran mixed conifer ecosystem
to similar ozone exposures. This work will extend beyond the San Bernardino
data set by using a design that includes two levels of soil moisture
Ponderosa pine trees growing
in mesic and xeric microsites at similar elevations will be selected
for this study. The differences in summer water availability will be
used to drive differences in ozone uptake. The mesic sites will extend
stomatal opening later on both a diurnal and seasonal basis, thus increasing
ozone uptake as compared to the xeric microsites. Within each microsite,
five blocks of ten trees will be fertilized at the rate of 50 kg ha-1
and five blocks will receive no fertilizer. Background N deposition
levels have been estimated to be approximately 9 kg ha-1
yr-1. Statistical comparisons of tree response variables
will be made within a soil moisture level across fertilizer treatments
(background and elevated N), and between soil moisture levels in unamended
blocks. The proposed study would make a major contribution in evaluating
whether N deposition, at current and potentially higher future levels
mitigates a known environmental stressor (oxidant pollution) in the
Sierran mixed conifer zone.
An additional supporting
objective is to quantify and determine the extent to which ozone exposure
and N deposition co-vary at four sites along an elevational gradient
in the Sequoia/Kings Canyon National Park from 580 m to 2900 m.
The specific objectives
of the study are to (1) test whether N deposition mitigates foliar oxidant
injury and associated tree response variables in ponderosa pine at two
different levels of ozone, (2) describe the effects of soil moisture
availability and N amendment on available soil N forms (ammonium and
nitrate) and on various foliar N attributes, and (3) quantitatively
correlate nitrogen deposition with ozone exposure along an elevational
REPORT: Does nitrogen mitigate ozone injury in Jeffrey pine?
Nancy Grulke Publications
Grulke NE 2003 Physiological
basis of ozone injury assessment in Sierra Nevadan conifers. In:
Bytnerowicz A, Arbaugh M, Alonso R. Assessment of ozone distribution
and its effects on Sierra Nevada ecosystems. Elsevier Publishers, The
Hague, Netherlands (in press).
2002 Sequoia-Kings Canyon PRIMENet Meeting Presentation handout
2001 PRIMENet Meeting Presentation: Canopy
transpiration of Jeffrey pine in mesic and xeric microsites: Implications
for O3 uptake (Nancy Grulke)
Grulke, N. E., R. Johnson, et al. (2003). "Variation in morphological
and biochemical O3 injury attributes of mature Jeffrey pine within canopies
and between microsites." Tree Physiology 23: 923-929.
Tausz, M., K. Herbinger, et al. (2002). "Antioxidant status of
Pinus jeffreyi needles from mesic and xeric microsites in early and
late summer." Phyton 42(3): 201-207.
Grulke, N. E. (2003). The physiological basis of ozone injury assessment
attributes in Sierran conifers. Ozone air pollution in the Sierra Nevada:
distribution and effects on forests. A. Bytnerowicz, M. J. Arbaugh and
R. Alonso. New York, Elsevier.
Grulke, N. E., R. Johnson, et al. (2003). "Canopy transpiration
of Jeffrey pine in mesic and xeric microsites: O3 uptake and injury
response." Trees 17: 292-298.
Grulke N. E., Johnson R, Monschein S, Nikolova P, Tausz M 2003 Variation
in morphological and biochemical ozone injury attributes of mature Jeffrey
pine within canopies and between microsites. Tree Physiology 23:923-929.