Long road to recovery for Tahoe Basin forests
Editor’s note: This is the third installment in the Tahoe Daily Tribune’s examination of the Tahoe Regional Planning Agency’s five-year evaluation of Lake Tahoe’s environment. Today, a look at the basin’s plant life.
A century of human activity in the Tahoe Basin has created an artificial forest that will require decades of intervention to restore to a more natural, healthy condition.
In the meantime, efforts to preserve individual plant species and plant communities have been largely successful.
Those are several of the conclusions about Lake Tahoe’s vegetation contained in the Tahoe Regional Planning Agency’s 1996 Evaluation of the basin’s environment.
In the agency’s five-year review of progress toward achieving nine environmental standards, protecting the basin’s plant communities is described as one of the largest challenges, said Steve Chilton, a TRPA division chief who supervised the report’s section on vegetation.
“What we’re trying to do is restore the forest, and that takes nearly as much time as it did to get it out of synch with the natural equilibrium of a healthy forest,” Chilton said.
Beginning in the early 1860s, much of the Tahoe Basin’s forest was leveled to satisfy the demand for timber and fuel at the mines of the Comstock Lode. By the time the forest began to return, public agencies had adopted a policy of suppressing the fires that regularly swept through the Sierra Nevada.
Together, the clearcutting and fire suppression transformed the basin’s forest, reducing the natural diversity of species and producing large swaths of uniformly aged trees.
Recent research has demonstrated that frequent fires thinned many of the younger trees, keeping the forest density low and producing an open, park-like appearance.
Guided by a consensus group of foresters that has studied the health of the Tahoe Basin forest, the TRPA is proposing a new approach to restoring forest health called ecosystem management. The goal is to use controlled fires, thinning of overstocked stands and replanting to recreate the type of forest that existed in the basin before the arrival of Europeans.
The U.S. Forest Service has adopted the strategy in two major forest-health projects on the basin’s east and north shores, but the effort will become more sophisticated as the TRPA refines the advanced computer models that mimic the basin’s forests.
“The model tells us what the potential natural vegetation should be for any place in the basin,” Chilton said. “We could cut decades off the process if we can be more specific.”
One target of the evaluation program is to define the characteristics of an old-growth, or late-successional, forest. The forest health group has proposed a standard of four trees per acre with breast-height diameters of 30 inches, or stands that exhibit signs of decadence. Such areas would be preserved as a core old-growth area, with natural corridors connecting with other areas for wildlife.
While forest managers will need decades to begin to restore Tahoe’s forests to a more-natural condition, the TRPA reported some successes in preserving uncommon plant species and sensitive plants. The agency concluded that most of the uncommon species have held their own, partly because they grow in protected or seldom-visited locations.
But researchers have expressed concern that deep-water plants beneath Lake Tahoe’s surface may be harmed by the lake’s declining clarity, which reduces the available sunlight. The TRPA plans to conduct a study of the lake’s depths with a remotely operated vehicle when the funds are available.
Of the sensitive plants identified in the agency’s 1991 Evaluation, one (carex paucifructus) has been removed from the listing because it may never have existed in the basin.
Of the others, no major impact to the populations has been identified except for the Tahoe yellow cress, or Rorippa subumbellata, a plant that thrives in the sandy belt between the lake and the forest. With Lake Tahoe rising to its maximum level since the 1991 Evaluation, the plant has lost a significant amount of its habitat, the report concluded.
Chilton said the restoration and preservation of the basin’s vegetation is perhaps the single largest challenge to Tahoe Basin regulators.
“We’re talking about vegetation that ranges from 500 feet below the surface of Lake Tahoe to the top of Freel Peak, and everywhere in between.”
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