Forestry officials seeking compromise unanimously approved six-month rules Wednesday to limit tree cutting near Northern California's rivers and streams.The state Board of Forestry's action drew mixed reviews from loggers and a quick hit from environmentalists.The board said it will develop permanent rules to take effect in 2001 and will base those rules on an exhaustive examination of logging's impact on fish and wildlife in fragile watersheds-something loggers, fishing interests, scientists and environmentalists urge.