Trinity County, California
Submitted by: Mary Ann Vinton
In 1972, Roger Eckart and his siblings bought a grandfathered-in piece of private land within Trinity National Forest in northern California, that same year the first Landsat satellite was launched. Over the past 40 years, both Eckhart and the Landsat series of satellites together observed the change in both land cover and land use across the region's mostly forested land. During this period, timbers harvesting practices and policies have combined with new fire patterns greatly affecting the regional land cover.
During the first half of the Landsat era, Trinity National Forest was a supplier of timber to wood based industries. They supplied wood from many tree species, but mostly from conifers. The preferred way to harvest wood then was what was called "even age management," but is more commonly known as "clear cutting" where complete parcels, or "stands," were cut down all at the same time.
Landsat observes forest disturbance well, especially clear cutting of closed canopy forest, because the leaves or needles that make up a treetop, or "crown" reflect light back strongly in the green and infrared bands of the electromagnetic spectrum. When vegetation is clear cut more the light is reflected back from bare soils, rock, and what's called dead tree slash, which is of branches, bark and other parts of the tree not retained for use. These regions appear as bright white areas of various sizes.
The harvested areas in this part of northern California typically remain brighter as seen in the Landsat imagery as seedling trees establish, then turning a lighter green hue as the young trees grow; older stands are a dark green. In this part of Trinity National Forest, typically 10 to 20 years pass between clear cutting and the forest patches returning to what most analysts would call "forest." The ability to clearly see forest cutting in this part of the Pacific Northwest is typically scale dependent and the full impact of wood harvesting forest change is much more noticeable at local scales.
USGS analysis of the area within about six miles in any direction of Eckhart’s property indicate that approximately 4.4 percent of the land cover was affected by change between 1973 and 1994. The vast majority of it is associated with wood harvested through clear cutting. Within this area, dozens of small- to medium-sized clear cuts show up where the trees were cleared and then slowly regrown.
Although the total amount of forest land cover never decreased much at any one time, the composition of forest age and species variety greatly changed, especially in the broader Pacific Northwest region. The overall amount of "old growth" forest steadily declined over time and concerns about the ecosystem’s ability to provide its long standing goods and services have been raised, especially in the environmental science communities.
Image: Credit: USGS EROS Data Center
Caption: Roger Auch, Research Geographer, USGS EROS Data Center
