Klamath-Siskiyou

Forested lands decreased in the Klamath-Siskiyou ecoregion between 1972 and 1992 while fragmentation increased on both private and public lands. Fragmentation rates on public lands were high for all basins, especially for the Rogue.

The Klamath-Siskiyou ecoregion, located in southwest Oregon and northwest California is an area of extraordinary biodiversity (Whitaker 1960), recognized by the World Conservation Union (IUCN) as an area of global botanical significance and classified by the World Wildlife Fund (WWF) as a global 200 site (Ricketts et al. 1999). To better understand changes in this important region, Staus and collaborators (2002) classified North American Landscape Characterization (NALC) imagery as “forest” or “non-forest” and examined forest change between 1972 and 1992. The study: 1) quantified rates of change in forest cover for the 20-year period, 2) characterized changes in forest cover by fifth level watersheds, and 3) described the fragmentation pattern of public and private forest landscapes within three major river basins in the ecoregion (Eel, Klamath, and Rogue).

The majority (approximately 90%) of the 9.5 million hectare (ha) Klamath-Siskiyou ecoregion remained unchanged between 1972 and 1992, with approximately 60% of the region remaining forested for the entire 20-year period. Overall, forests covered 66.8% of the ecoregion in 1972 and 62.1% in1992. Forest disturbance affected 11.4% of the forest area.

The Klamath-Siskiyou ecoregion contains a total of 196 fifth-field watersheds (drainages that average around 50,000 ac in size). Forest disturbance within these fifth level watersheds ranged from 0.0 – 93.2% but averaged 13.2%. Approximately half of the ecoregion’s area was identified as having low (<10%) forest disturbance, 39% showed moderate (10-25%) forest disturbance, and 11% showed high (>35%) levels. Watersheds in the northeastern portion of the ecoregion and along the Oregon coast showed the highest disturbance levels (Figure 1).

For the three river basins (Eel, Klamath, and Rogue) where spatial pattern of forest disturbance was analyzed, private lands were already more fragmented than public lands in 1972. Over the 20-year time period, forest fragmentation increased on all ownerships. Fragmentation rates on public lands were high for all basins especially the Rogue. Clearcut logging on private lands was generally in larger adjacent tracts, whereas cuts on public lands were generally smaller and more dispersed.

These results illustrate the importance of considering landscape change history when planning for effective biodiversity conservation in forested ecoregions and when formulating ecologically sustainable forest management strategies.

References:

• Rickets, T., Dinerstein, E., Olson, D., Loucks, C., Eichbaum, W., and D. DellaSala. 1999. A conservation assessment of the terrestrial Ecoregions of North America. Volume I – The United States and Canada. Island Press, Washington, DC, USA.
• Staus, N., Strittholt, J., DellaSala, D. and R. Robinson. 2002. Rate and pattern of forest disturbance in the Klamath-Siskiyou ecoregion, USA between 1972 and 1992. DOI: 10.1023/A:1021274701133.
• Whitaker, R.H. 1960. Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monographs 30:279-338. DOI: 10.2307/1943563.