An assessment of windbreaks in central Wisconsin

Soil erosion by wind is a persistent problem in central Wisconsin. The exte nt and effectiveness of windbreaks in erosion- prone areas are unknown. We investigated the potential effectiveness of windbreaks established for soil erosion control in Portage County, Wisconsin. Our objectives included quan tification of their extent and condition, development of a routine method f or field assessment, and compilation of a reference database of windbreak i nformation. We used aerial photographs to identify the windbreak population , and a two-stage, stratified random sampling technique to obtain samples f or field evaluation. Variables and attributes examined included species, nu mber of gaps, height, width, porosity, spacing, live crown ratio, crown con dition, and a condition rating. Methods included simple photo-interpretatio n techniques, field measurements, optical scanning techniques, and data man ipulation in geographic information systems. We identified over 2600 windbr eaks comprising a total extent of 834 km; only a small proportion of this m ay offer effective protection at critical periods. Collectively, field wind breaks protect a very small proportion only of the county's agricultural la nd area from wind erosion. These results imply a need for increased plantin g rates, explicit maintenance or renovation of existing barriers, and windb reak designs that are both sustainable and compatible with current agricult ural production efforts.