Simulations of pre- and post-harvest soil temperature, soil moisture, and snowpack for jack pine: comparison with field observations

Quantifying temporal changes in soil temperature and moisture conditions is an important part of characterizing pre- and post-disturbance conditions t hat influence the health, productivity, and sustainability of forest ecosys tems. In this paper, we present an experimental case study that was used to evaluate the ability of the forest hydrology model ForHyM2 to simulate fie ld-observed changes in root-zone soil moisture and temperature, as well as snowpack depth, throughfall volume and forest floor percolate volume, for a jack pine (Pinus banksiana Lamb.) site in northeastern Ontario. The experi ment refers to two post-harvest treatment factors, each involving two treat ments: (a) blading (removing) or non-blading the forest floor and part of t he mineral topsoil, (b) herbiciding or non-herbiciding. It was found that h arvesting increased the average daily soil temperature by 4-6 degreesC on a ll treatment plots during summer (5 cm soil depth). Blading increased the s oil temperature further by 1-2 degreesC. Herbiciding did not have significa nt effects on soil temperature. Eliminating competing forest vegetation sig nificantly increased soil moisture level on the non-bladed treatment plots. The model simulations were based on daily precipitation (snow and rain), ai r temperature, and a few site descriptors such as longitude and latitude, s oil depth, soil texture, and leaf area index. The resulting simulations com pared well (graphically) with the pre- and post-harvest field observations regarding soil moisture, soil temperature, and snowpack water equivalents. Good graphical agreements suggest that the approach taken with this case st udy can be applied to the evaluation of soil moisture and temperature condi tions to a variety of pre- and post-disturbance forest conditions. The resu lts from the study would be useful for addressing below ground processes su ch as root growth, soil respiration, rate of organic matter decomposition, rate of soil weathering, nutrient cycling, etc., all of which strongly infl uence site productivity. (C) 2000 Elsevier Science B.V. All rights reserved .