APPLICATION OF CALCIUM TO LAND IMPACTED BY ACID DEPOSITION IN THE WEST-CENTRAL ADIRONDACK MOUNTAINS: RESPONSE OF SOIL AND BIOTIC COMMUNITIES

A century of acid deposition has resulted in changes to soil, soil water and surface water chemistry in the Adirondack Mountains of New York state. In the soils it appears that depletion of exchangeable base cations, especially calcium, has occurred over many decades and base saturation, in general, has declined. The purpose of this study was to measure and monitor the geochemical and biological effects of adding calcium back to soil in forested plots in the Adirondack Mountains, a region that has been shown to have experienced considerable calcium-depletion in soils.

Five sites in the west-central Adirondacks were chosen for manipulation in this study, all within the Moose River watershed. At each location, two circular plots, each with an area of 1590 square meters were delineated. One plot was left as a control and powdered limestone was applied by hand to the second (experimental) plot in the amount of 10 tonnes/ha at three different times (fall 2005, spring 2006, fall 2006). Soils in all of the limed sites were re-sampled yearly after final application of the limestone and analyzed for pH, exchangeable cations and exchangeable acidity. At two of the five locations, soil solutions were also regularly collected after liming using wick and suction lysimeters. Soil solutions were analyzed for pH and basic cations. Calcium content in overstory leaves was also tracked for three years after application of limestone at the sites and invertebrate communities were monitored for both changes in species abundance and calcium concentrations.

As expected, pH in the upper soil horizons increased appreciably after the application of limestone. Over time, that effect is translated lower into the soil profile. Similarly, exchangeable calcium increases in the upper horizons of the treated soils, although the movement of exchangeable calcium downward is slow – over a three year period, increases in exchangeable calcium are seen only to a depth of 10-15 cm from the surface. Overstory leaves in limed plots contained more calcium than unlimed plots, with some species (e.g. yellow birch) responding more positively to liming than others. Calcium concentrations of soil invertebrates were variable among taxa, with millipedes containing a far greater concentration of calcium than others that were sampled.