Noninfectious Disorders
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Windthrow

Windthrow is most common when soils are shallow and/or water saturated. Spring is very windy throughout much of the Southwest, and is the time when blowdown occurs in many root diseased infected areas. Blowdown is also prevalent in winter months when trees are loaded with snow.

More severe windthrow damage takes place with tornadoes and microbursts, which occasionally occur in northern Arizona. Tornadoes and microbursts both result in windthrown trees lying parallel to one another in the same direction as the storm. Tree species with shallow root systems (e.g. spruce) are more prone to windthrow.

Reference:  107

Figure 289. There are typically decay or soil defects associated with windthrown trees.
Figure 290. Tornadoes and microbursts have been known to knock down a swath of trees.