『Abstract
Northern hardwood forests in the eastern US exhibit species-specific
influences on nitrogen (N) cycling, suggesting that their phosphorus
(P) cycling characteristics may also vary by species. These characteristics
are increasingly important to understand in light of evidence
suggesting that atmospheric N deposition has increased N availability
in the region, potentially leading to phosphorus limitation. We
examined how P characteristics differ among tree species and whether
these characteristics respond to simulated N deposition (fertilization).
We added NH4NO3 fertilizer
(50 kg ha-1 year-1) to single-species plots
of red oak (Quercus rubra L.), sugar maple (Acer saccharum
Marsh.), eastern hemlock (Tsuga canadensis (L.) Carr.),
American beech (Fagus grandifolia Ehrh.), and yellow birch
(Betula alleghaniensis Britt.), in the Catskill Mountains,
New York from 1997 to 2007. Species differences were observed
in foliar, litter and root P concentrations, but all were unaffected
by a cumulative N fertilization of 550 kg/ha. similarly, measures
of soil P availability and biotic P sufficiency differed by species
but were unaffected by N fertilization. Results suggest species
exhibit unique relationships to P as well as N cycles. We found
little evidence that N fertilization leads to increased P limitation
in these northern hardwood forests. however, species such as sugar
maple and red oak may be sufficient in P, whereas beech and hemlock
may be less sufficient and therefore potentially more sensitive
to future N-stimulated P limitation.
Keywords: Catskill Mountains; Nitrogen; Nutrient limitation; Temperate
forest』
Introduction
Methods
Site description
Field sampling
Lab methods
Statistical analysis
Results
Plant tissue
Soil moisture and pH
Extractable inorganic and organic P
Enzyme activity
Microbial biomass P
P fractionation
Species profiles
Discussion
Species' P profiles and comparison to N profiles
Resorption and plant nutritional status
Links among biogeochemical cycles with N fertilization
Differences in soil P due to species and fertilization
Hemlock, P limitation and pests
Conclusions
Acknowledgments
References