American Landscapes - Trinity County, California, Submitted by Roger Eckart
Forest fires and logging are the two main drivers of change in this area within Trinity National Forest in northern California. Mr. Roger Eckart and his siblings bought a grandfathered-in piece of private land within the forest in 1972 and so together the Eckart family and the Landsat program has observed changes in the forest for more than 40 years.
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.
This timelapse of four Landsat images shows the amount of change around the Eckart property in Trinity National Forest in Northern California. The first image marks the deforested areas in 1973 (in yellow), in a 20 kilometer square centered on the Eckart property. The second image is in 1980 and it marks all the areas that have changed classification since 1973. Images that have changed once are in yellow since 1973 , those that have changed twice are in blue, and those that have changed three times are in red. The third image is in 1987, and the fourth is in 1994. (Credit: NASA's Goddard Space Flight Center/USGS) › Download this video in broadcast quality from NASA Goddard's Scientific Visualization Studio
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.
Another trend affecting forest land cover in northern California, but not directly linked to changes in public forest policy, is the increasing incidence of large wildfires. Scientific research has linked the timing of earlier spring snowpack melt with longer fire seasons and the potential for larger fires. Starting in the mid-1980s, fires became more frequent in northern California and the trend has continued into the new century.
Eckart mentions three large wildfires that have occurred near his property between 1999 and 2008. Landsat’s wide view can show these fires and their aftermath across time. The first fire was the Big Bar Complex that burned over 150,000 acres (about 600 square kilometers) in the summer and fall of 1999. A Landsat image from the following spring, collected on May 21, 2000, shows (with bands 7-4-3) areas of severe burning; the deep pink color indicates bare ground and water stressed vegetation. The surrounding green is unburned forest.
A similar sized fire, the Bar Complex, occurred nearby in 2006. As seen in a Landsat image from October 13, 2006, the fire is still smoldering in its northeast corner. The pinkish fire scar of more intense burning, seen again in bands 7-4-3, is quite visible.
The last major fire was the Iron and Alps Complex in 2008. In this Landsat image from Aug. 15, 2008, the fire is still in progress and its telltale smoke plumes show the active area of the fire perimeter. Heavily burned areas from the older Bar Complex fire are still visible just north and slightly east of the main smoke plume of the current fire. The previously dark pink areas of more severely burned areas from the 2006 fire have changed to a lighter pink as fresh ash and charred wood have weathered and pioneer herbaceous vegetation species colonized the affected land.
Whatever the future holds for the forested landscape of Trinity County, Calif., it will mostly likely involve the dynamics of land cover change.