о 20 40 60 80 100 20 40 60 80 200 20 40 60 80 300 AGE IN YEARS Figure KLAMATH SUSTAINED YIELD UNIT 1-10 EMPIRIC YIELD CURVES HIGH INTENSITY LANDS SOURCE: BLM Forest Inventory 1968 & 1977 CLIMATE 2. DESCRIPTION OF THE ENVIRONMENT This chapter addresses the environment as it exists today within the Jackson and Klamath Sustained Yield Units (JKSYUS, SYUs). Since intensive timber management has been practiced within the SYUS for several decades, the environment described is seldom natural or pristine but exhibits the effects of human use. Chapter 2 provides a basis on which impacts of the proposed action may be assessed. In preparation of this chapter those elements of the environment which might be affected were addressed. Additional background information is included only to the extent necessary to provide the basic picture. The future environment without the proposed action is considered to be the environment that would result from continuation of the existing timber management plan for the SYU. Continuation of that plan and the environment that would result are addressed as the "no-action" alternative in Chapter 8. In preparation of this chapter the primary data sources are documents of the Bureau planning system developed for the Jackson-Klamath Planning Area, which is comprised of the Rogue, Butte Falls, and Klamath Resource Areas. The Unit Resource Analysis, Planning Area Analysis, and preliminary Management Framework Plan for Jackson-Klamath Area are available for review at Medford District Office, 310 West 6th Avenue, Medford, Oregon 97501. Other references supplementary to or updating planning system data are cited within the body of the text by author and date of publication. A listing of these references appears in the References Cited. 2.1 CLIMATE The climate of the Jackson and Klamath Sustained Yield Units is transitional between the Mediterranean climate to the south and the marine-mesothermal climate to the north. Winters are cool and wet, and summers are warm and fairly dry. Altitude, aspect, and wind patterns, however, may alter this general climate over a small area. Figure 2-1 shows weather stations and mean annual precipitation throughout the planning unit. Table 2-1 gives climatic data for some of the representative stations. Climatic conditions in the planning area do not generally create good dispersion conditions for air pollutants. Light winds (3-6 mph) prevail in Bear Creek Valley throughout the year. The height to which turbulence mixes and disperses pollutants in the airshed varies throughout the year. In the Medford area, the afternoon mixing height is usually greater than 4,000 feet from March through September and then drops to a low of 1,500 feet in December before rising again in January and February. |