Surface compaction estimates and soil sensitivity in aspen stands of the Great Lakes States.

摘要

Aspen forests in the Great Lakes States (USA) support much of the regional timber industry. Management-induced soil compaction is a concern because it affects forest health and productivity and soil erosion. Soil compaction increases bulk density and soil strength and can also decrease air and water movement into and through the soil profile. Currently, most inventories, and specifically the Forest Inventory and Analysis (FIA) programme, use qualitative estimates of soil compaction. This study compared qualitative estimates with quantitative measurements on aspen (Populus grandidentata and P. tremuloides) clearcuts in five national forests (Chequamegon-Nicolet in Wisconsin, Huron-Manistee and Ottawa in Michigan, and Chippewa and Superior in Minnesota) in the Great Lakes States region. Research sites were stratified into classes of high and low potential for soil compaction on the basis of soil texture. Qualitative visual assessments of compaction were made according to FIA phase 3 protocols and compared with physical measurements of bulk density, soil compression strength, and saturated hydraulic conductivity. No differences in compaction between high- and low-risk soils were detected using visual assessments, but quantitative measurements in high-risk, fine-textured soils indicated greater compaction than low-risk, coarse-textured soils. These results illustrate shortcomings in qualitative estimates of compaction made according to FIA phase 3 field protocols. Inexpensive quantitative measurements, such as those taken with a pocket penetrometer, may be sufficient to quantify compaction levels within the plots.