Foliar and sapwood nutritional and metabolic responses to Ca-treatment at the Hubbard Brook Experimental Forest, 2000 – 2015

Background Acidic deposition has caused a depletion of calcium (Ca) in the
northeastern forest soils. One time application of wollastonite
(CaSiO3 - 1.2 Mg ha-1 of Ca) was done at watershed 1 (WS1) of the
Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its
effects on various functions of the HBEF ecosystem. This rate of
application was intended to increase the existing base saturation of
the soil from 10% to approximately 19%, and to increase the soil pH to
the level that was estimated to exist ~50 years prior to treatment.
More details on the treatment can be found at
http://www.hubbardbrook.org/research/longterm/calcium/w1_overview/index.html.
The overall objective of this study was to evaluate changes in foliar
and sapwood metabolic parameters and microbial diversity as indicators
of stress and overall health in trees exposed to Ca-supplementation.
Raw data from Ca-treated WS1 are compared with WS3 (reference
watershed) for cellular metabolites, exchangeable foliar chemistry
(not totals) 2000-2015. These watersheds are in close proximity (less
than 1.5 Km apart) with similar geology, temperature, soils, and
overall climate. For more details see a list of references given below Ca-Supplementation-Metabolic Study (WS1 & along eastern edge of
WS3) SUMMARY: The effects of Ca addition on foliar soluble (extractable in
5% HClO4) ions, chlorophyll, polyamines, and amino acids were studied
in three hardwood species, namely sugar maple, yellow birch, and
American beech. We further analyzed these effects in relation to
elevation at Ca-supplemented WS1 and reference WS3 watersheds. During
the earlier years foliar soluble Ca increased significantly in all
species at mid and high elevations at Ca-supplemented WS1. This was
accompanied by increases in soluble P, chlorophyll, and two amino
acids, glutamate and glycine. A decrease in known metabolic indicators
of physiological stress (i.e. the amino acids, arginine and
γ-aminobutyric acid (GABA), and the diamine, putrescine) was also
observed. In general, these changes were species-specific and occurred
in an elevation dependent manner. Despite an observed increase in Ca
at high elevation for all three species, only sugar maple exhibited a
decrease in foliar putrescine at this elevation indicating possible
remediation from Ca deficiency. At higher elevations of the reference
WS3 site, foliar concentrations of Ca and Mg, as well as Ca:Mn ratios
were lower, whereas Al, putrescine, spermidine, and GABA were
generally higher. Comparison of metabolic data from these three
species reinforces the earlier findings that sugar maple is the most
sensitive and American beech the least sensitive species to soil Ca
limitation. Furthermore, there was an increase in sensitivity with an
increase in elevation. These data were gathered as part of the Hubbard Brook Ecosystem Study
(HBES). The HBES is a collaborative effort at the Hubbard Brook
Experimental Forest, which is operated and maintained by the USDA
Forest Service, Northern Research Station.