Noninfectious Disorders
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Red Belt
Figure 288. Figure 288. A band of cold air gets trapped at a specific elevation around mountains.

Red belt, another type of winter damage, is named because of the appearance of red needled trees distributed in well-defined bands varying from less than 20 to as much as 1,000 yards wide on slopes and benches. These events are associated with the sudden occurrence of warm, dry winds (e.g. Chinook winds) that produce a temperature inversion. A relatively thin layer of warm air arrives that cannot mix downward and continues to contact side slopes. Trees exposed to unseasonably warm air by day receive seasonably cold air at night. This alteration of warm and cold air exposure, along with the frozen condition of the soil, results in desiccation injury because daytime transpiration removes moisture from the needles more rapidly than roots in frozen soil can replace it. Later, older needles fall off, leaving only current year needles on living branches after bud-break.

References:  83, 93