California tree seed zones

California forest tree seed zones were established originally by Fowells (1946), with revisions by Roy (1963) and Schubert (1966). The Forest Tree Seed Committee of the Northern California Section, Society of American Foresters, has revised the original zones and updated the recording systems described in the earlier reports. The Forest Tree Seed Committee acknowledges the assistance of foresters and tree seed dealers in California and the Pacific Northwest who reviewed the revised zone map and reporting system. The California Tree Seed Zone map is an integral part of the se3ed collection reporting system. Zones are delineated on the basis of collection criteria adopted in the USDA forest seed policy of 1939. The policy specifies that seed should 1) be collected within 100 miles north or south of the planting site and 2) differ in elevation by less thant 1000 feet. Also, 3) careful consideration should be given to areas having a unusual climatic, topographic, or soil conditions that might greatly affect tree growth. On the basis of these three criteria, the State was divided into six physiographic and climatic regions, 32 subregions within regions, and 85 seed collection zones. One region is divided into four physiographic and climatic ares having 18 of the 85 zones. Seed collection zones are limited to about 50 miles in latitude. Where possible, boundaries have been chosen to follow natural features, such as crests of mountain ranges, ridgetops, and rivers, or physical features such as highways, canals, and railroads. The seed collection zones and three-digit method of designating the various zones are coordinated with the map and coding system developed by the Western Forest Tree Seed Council in 1966 and now used in Oregon and Washington.