Differential impacts of calcium and aluminum treatments on foliar and sapwood nutrition and metabolism of sugar maple trees growing at the west edge of WS6 of the Hubbard Brook Experimental Forest from 1997-2009.

Plot levels Ca and Al additions study at WS6 BACKGROUD: To better evaluate the interaction of Ca depletion and Al
mobilization on a northern hardwood forest, the Nutrient Perturbation
(NuPert) study was initiated in 1995, west of the biogeochemical
reference watershed (W6) at the HBEF (43.95411°N, 71.74779°W). The
study area is on a south-facing slope, with an elevational range of
700–760 m, and most soils are classified as either Aquic Haplorthods
or Aquic Haplumbredts (Halman et al. 22015 and references therein).
Twelve sugar maple ( Acer saccharum Marshall)
dominated plots (45 m × 45 m) were randomly assigned to one of three
treatments (Ca addition, Al addition, or control (no addition)),
yielding four replicates of each treatment in the study. In addition
to sugar maple, American beech ( Fagus grandifolia Ehrh.) and yellow birch ( Betula alleghaniensis Britt.) are co-occurring tree species in these plots, whereas
hobblebush ( Viburnum lantanoides Michx.) and
striped maple ( Acer pensylvanicum L.) dominate
the understory. Treatments began in 1995 with annual CaCl2 (2.5 g·m−2)
and AlCl3 (0.9 g·m−2) applications occurring each fall or spring
during leafless periods. The use of CaCl2 was halted in 1999 in favor
of a one-time application (38 g·m−2) of wollastonite (CaSiO3, a
slow-release form of Ca). Thereafter, AlCl3 additions occurred in
alternate years in fall or spring. Foliage was collected from sunlit
branches in the upper to mid canopy dominant sugar maple trees. Five
trees per plot of each group were selected for sampling in August
2008. There was an ice storm in 1998 at this site which might have
interfered with this study findings. In 2009, tiny sapwood plugs were
also collected. All the analyses were carried out using the procedures
described under section A (Ca-supplementation study). SUMMARY: Acid deposition induced losses of calcium (Ca) from
northeastern forests have had negative effects on forest health for
decades, including the mobilization of potentially phytotoxic aluminum
(Al) from soils. To evaluate the impact of changes in Ca and Al
availability on sugar maple foliar and sapwood nutrition and
metabolism at the Hubbard Brook Experimental Forest (Thornton, New
Hampshire) in control and amended with Ca or Al plots beginning in
1995. Observations were taken from 1997-2009 at various intervals.
Plots were mainly composed of sugar maple. The Ca:Al sensitivity of
sugar maple contributed to divergent growth patterns that influenced
stand productivity and composition. Given that acidic inputs are
expected to continue, the growth dynamics associated with Al treatment
may have direct relevance to future conditions in native forests.
Study site The HBEF has long been documented as a site exposed to
acidic inputs and subsequent Ca depletion (Bormann and Likens 1979;
Likens et al. 1998). (Unpublished data) Likens GE, Driscoll CT, Buso DC, Siccama TG, Johnson CE, Lovett GM,
Fahey TJ, Reiners WA, Ryan DF, Martin CW, Bailey SW (1998) The
biogeochemistry of calcium at Hubbard Brook. Biogeochemistry 41:89–173 Bormann FH and Likens, GE (1979) Pattern and Process in a forested
ecosystem. Springer-Verlag NY Inc. 253 pp