Soil quality assessment in domesticated forests - a southern pine example

Maintenance and enhancement of soil productivity is central to the long-ter m success of intensive forest management. A simple technique is required fo r monitoring the effects of different management practices on soils as an a id in developing codes of practice that foster maintenance and enhancement of soil productivity. The objective of our work was to determine if managem ent impacts on soil productivity could be assessed using the soil-quality c oncepts developed in agriculture. A soil-quality index (SQI) model, that me asures the effects of management practices on five key growth-determining a ttributes of forest soils. namely (1) promote root growth, (2) store, suppl y and cycle nutrients, (3) accept, hold, and supply water, (4) promote gas exchange, and (5) promote biological activity, was developed and rested as part of a controlled study in intensively-managed pine plantations on the L ower Coastal Plain of South Carolina. Three 20-ha, 20-year-old loblolly pin e plantations were harvested under wet and dry conditions to create a broad gradient in soil disturbance. Within each harvested plantation, a subset o f 3-ha plots were site prepared by either bedding or mole-plowing plus bedd ing, then all sites were established as third-rotation pine plantations. Fi eld data were collected spatially for soil bulk density, net N mineralizati on, water table depth, soil aeration, and soil moisture. Literature-based s ufficiency values were determined for each property and substituted into th e SQI model as surrogate indicators for the five key attributes, thus obtai ning spatial SQI predictions within each harvesting and site preparation tr eatment. Our study results demonstrate how SQI monitoring could be used to identify the effects of management practices on soil productivity, which sh ould aid in developing codes of practice as a component of achieving long-t erm sustainability in domesticated forests. (C) 1999 Elsevier Science B.V. All rights reserved.