Effect of Forest Operations Systems on the Ecological Processes of Forest Ecosystems

 

Forest operations are prescribed to implement silvicultural management objectives and may affect critical biological, chemical, and physical processes that sustain soil-plant ecosystems. The extent and long-term implications of anthropogenic disturbances through forest operations are not well characterized to fully understand the specific changes and their role in long-term sustainability. Numerous investigations have established relationships among machine systems, machine components, and soil impacts, but an incomplete understanding of the machine-soil interaction and the impact on soil sustainability and productivity still exists. Actions which alter soil physical properties have direct and indirect impacts on the soil’s ability to provide essential nutrients, adequate air and water supplies, and the physical framework to support adequate biological response. The overall result can be a loss or reduction of soil and site productivity which cannot be fully restored by mechanical and/or chemical amelioration. A significant challenge exists to understand more completely the complex machine-soil interaction in terms of temporal, spatial, vegetative, site and climatic differences, and to integrate the results into a comprehensive systems approach to management for sustained above and belowground productivity.

Disturbances are imposed on forest systems by forest operations through repeated trafficking and ground-disturbing operations in the course of harvesting, site preparation and regeneration activities. The stresses applied to impacted soils are typically expressed in terms of changes in select soil physical properties including bulk density, porosity, water content and soil strength. These measures of soil compaction often do not fully convey the changes in soil structure and nuturient dynamics which can impact soil nutrient capacity, aeration status, water infiltration, water availability, organic matter sequestration and decomposition, and rooting potential. Soils subjected to compaction experience higher packing density at the expense of large voids favoring the formation of more water holding, or capillary pores, but reducing infiltration, hydraulic conductivity, air exchange, nutrient supply, root growth, and microbial activity. The net result is a soil environment with lowered capacity to supply essential nutrients and water, lowered biological productivity, and increased erosion potential. Tillage systems are employed with greater frequency to improve soil physical conditions for improved air and water infiltration and lowered soil strength but further degradation of soil qualities is often the result with loss of aggregate stability, accelerated decomposition of organic matter, loss of essential nutrients, and exposure of important microbial communities to increased temperature and dessication.

Hydrological impacts also result from forest operations. Removal of vegetation affects evapotranspiration and soil temperatures, altering water cycling in the forest. Soil disturbance can either enhance or inhibit infiltration, affecting overland flow. Vegetative changes and the application of fertilizer or chemicals affect water chemistry. The complexity of water quality impacts requires integrated studies that evaluate multiple variables over several scales from microsite to watershed. Field studies will provide the basic data and process information to validate modeling tools for predicting the effects of forest operations across a range of conditions.

Current Projects:

 

Effects of Forested SMZ Management on Ecological Functions. Graeme Lockaby, Jack Feminella-Auburn University; Bob Rummer, Emily Carter-USDA Forest Service

Assessing Soil Physical Changes in a Harvested Landscape. Emily Carter-USDA Forest Service

Influence of Site Preparation on Soil Movement and Runoff. Emily Carter-USDA Forest Service

Slope Aspect Effects on Soil Properties and Timber Harvesting-induced Compaction in Piedmont Forests. Joey Shaw-Auburn University; Emily Carter-USDA Forest Service

Prescribed Burning and Soil Erosion in Longleaf Pine Restoration. Ken Farrish-SF Austin University; Emily Carter-USDA Forest Service

Impact of Harvesting and Thinning on Poorly Drained Systems. Wayne Skaggs-NC State University; John Grace III-USDA Forest Service

Timber Harvesting Effects on Quality and Spatial Variability. Emily Carter, USDA Forest Service

Harvesting/Site Preparation Influence on Soil Erosion on a Piedmont Soil in Alabama. John Grace III-USDA Forest Service

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