Strittholt James R, DellaSala Dominick A, Jiang Hong
Conservation Biology Institute, 260 SW Madison, Suite 106, Corvallis, OR 97333, USA.
Conserv Biol. 2006 Apr;20(2):363-74. doi: 10.1111/j.1523-1739.2006.00384.x.
Nearly 10 million ha of federal lands in the Pacific Northwest have been managed under the Northwest Forest Plan since 1994. The plan reduced logging levels by 80%; only recently, however have inventories on status and condition of mature and old-growth forests become available. Our objectives were to (1) determine the areal extent of old (> 150 years) and mature (50-150 years) conifer forests based on 2000 Landsat 7 ETM+ imagery, (2) examine levels of protection, (3) determine the degree of additional protection afforded to old and mature conifer forests if late-successional reserves (LSRs) and inventoried roadless areas (IRAs) were fully protected, and (4) review management options to achieve greater protection of older forests. The historical extent of old-growth forest in the Pacific Northwest was roughly two-thirds (16,672,976 ha) of the total land area. Since the time of European settlement, approximately 72% of the original old-growth conifer forest has been lost, largely through logging and other developments. Of the remaining old growth, the Central and Southern Cascades and Klamath-Siskiyou account for nearly half Mature conifer area (4,758,596 ha) nearly equaled the amount of old conifer More than 78% of the old growth and 50% of mature forest were located on public lands. Approximately one-quarter (1,201,622 ha) of the old-growth conifer (or 7% of the historical old-growth area) was classified as GAP status 1 (strictly protected) or GAP status 2 (moderately protected). The total area of LSRs was slightly more than 3 million ha, approximately 36% (1,073,299 ha) of which contained old-growth conifer forest. Combined old and mature conifer within LSRs was approximately 59% of the total LSR area. The total amount of IRA for the Pacific Northwest was approximately 1,563,370 ha; of this, 526,912 ha (34%) was old growth. The combined area of old-growth conifer forest accounted for by protected areas (GAP 1 and 2), LSRs, and IRAs was 2,401,780 ha, which accounts for 66% of the old-growth conifer forests on public land, 51% of the old conifer in the region, and 14% of the amount that occurred historically. Outside these land designations, an additional 1,240,271 ha of old growth are on other public land and another 1,023,392 ha are on private lands throughout the Pacific Northwest. Our results indicate the need to periodically monitor status and condition of older forests and strengthen protections of old growth in the region.
自1994年以来，太平洋西北地区近1000万公顷的联邦土地一直按照《西北森林计划》进行管理。该计划将伐木水平降低了80%；然而，直到最近，关于成熟林和老龄林现状及状况的清查数据才可得。我们的目标是：（1）基于2000年陆地卫星7号增强型专题绘图仪（ETM+）影像确定老龄（>150年）和成熟（50 - 150年）针叶林的面积范围；（2）检查保护水平；（3）确定如果对后期演替保护区（LSRs）和已清查的无路地区（IRAs）进行全面保护，老龄和成熟针叶林将获得的额外保护程度；（4）审查管理选项以实现对老龄林的更大保护。太平洋西北地区老龄林的历史范围约占总土地面积的三分之二（16672976公顷）。自欧洲人定居以来，大约72%的原始老龄针叶林已经丧失，主要是通过伐木和其他开发活动。在剩余的老龄林中，中南部喀斯喀特山脉和克拉马斯 - 西斯基尤地区占了近一半。成熟针叶林面积（4758596公顷）几乎与老龄针叶林面积相当。超过78%的老龄林和50%的成熟林位于公共土地上。大约四分之一（1201622公顷）的老龄针叶林（占历史老龄林面积的7%）被列为GAP状态1（严格保护）或GAP状态2（适度保护）。后期演替保护区的总面积略超过300万公顷，其中约36%（1073299公顷）包含老龄针叶林。后期演替保护区内老龄和成熟针叶林的总面积约占后期演替保护区总面积的59%。太平洋西北地区已清查无路地区的总面积约为1563370公顷；其中，526912公顷（34%）为老龄林。由保护区（GAP 1和2）、后期演替保护区和已清查无路地区所涵盖的老龄针叶林总面积为2401780公顷，占公共土地上老龄针叶林的66%，占该地区老龄针叶林的51%，占历史上出现面积的14%。在这些土地指定范围之外，另有1240271公顷的老龄林位于其他公共土地上，还有1023392公顷位于太平洋西北地区各地的私人土地上。我们的结果表明需要定期监测老龄林的现状和状况，并加强对该地区老龄林的保护。
