Effects of extensive forest management on soil productivity

Abstract

This paper focuses on the effects of extensive forest management on soil productivity, its capacity to produce plants. Forest productivity, the summation of the productivities of the individual landscape elements (stands) that comprise the forest, is the integration of soil productivity, climate, species composition and stocking, and stand history. Extensive forest management can be operationally defined by the monetary investment per unit area of land, or by the number of stand entries per rotation, or by a combination of those metrics. A stand entered once during a rotation, for harvest, is extensively managed while a stand that has been subjected to site preparation, planted with genetically improved stock, and thinned and fertilized is intensively managed. The distinction blurs between those extremes. Many reviews have summarized the effects of forest harvest, the major extensive management activity, on soil properties and hence on productivity. Rather than simply reiterating those reviews, I have framed the paper in a series of axioms (which all agree upon), corollaries (consequences to productivity that follow from the axioms and are also agreed upon), and postulates (proposed consequences that are subject to some uncertainty). It is axiomatic that forest management activities alter soil physical, chemical, and biological properties. Changes have been well-documented, although their intensity and duration varies among locations and associated soil and forest types. Consequences of the changes in soil physical properties are clearly corollaries, and include reduced productivity due to surface erosion, mass flow, soil compaction, and rutting and puddling. Although the negative consequences of roads and skid trails to stand-level productivity may be considered to be corollaries, extrapolations of those consequences to the landscape is less clear and should be considered to be postulates. Similarly, consequences of changes in soil chemical and biological properties due to forest management should be considered to be postulates; not fully tested. Although soil chemical and biological properties are changed by management, the duration of those changes and their influence on productivity are not clear. Forest ecosystems are dynamic and resilient. Assessment of the consequences of changes in properties should recognize that shifts in preferred species may not be equated with changes in soil productivity, and that short-term effects may not be indicative of longer-term effects. Both ethical and economic considerations demand good stewardship of our natural resources. Extensive forest management, if carried out with both wisdom and prudence, is not antithetical to good stewardship.