Point Reyes Light - October 19, 2000
Bishop pine forest recovering after 1995 fire; mountain beavers scarce
By Gregory Foley
Five years after the Inverness Ridge fire burned thousands of acres of Bishop pine forest and coastal scrub, the ecosystem is generally recovering well.
However, scientists have noted large-scale erosion in the burn area and the decline of certain insect and mammal species.
Most regional songbird species – except for those that nest in large trees – have remained stable or increased in number. But as a direct result of the fire, one rare and peculiar rodent – the Point Reyes mountain beaver – has sharply declined in population.
The findings come as part of the increased research done in the Point Reyes National Seashore focusing on the impact and recovery from fire in coastal habitat. Park officials describe all the research as the "silver lining" to the four-day blaze in October, 1995, that began on Mount Vision, razed 45 homes in the Paradise Ranch Estates subdivision, and ultimately scorched 9,100 acres of wilderness in the overall 12,000-acre burn area.
Scientists’ findings
At a Park Service symposium Saturday in Point Reyes Station, seven researchers presented their findings:
• Large mammals such as deer, foxes, and bobcats were not particularly harmed by the fire. However, large numbers of less mobile small mammals perished, reported US Geological Survey biologist Gary Fellers.
After finding a significant decline in the number of rodents and shrews immediately after the fire, Fellers discovered that most species began to recover within one year as groundcover and habitat improved.
However, one main casualty has been the Point Reyes mountain beaver, a primitive, burrow-dwelling rodent that lives primarily in thickets with diverse plant life. Its range is limited because it can’t concentrate its urine and must stay near water.
Fellers estimated that of a population of approximately 2,000 mountain beavers that had been limited to a 150-acre section of the burn area, only 20 individuals survived and annual checks have shown that the population is still very low.
Fellers predicts that the mountain beaver will recover gradually as the plant thickets reestablish themselves.
• Songbird populations in the burned areas of Muddy Hollow and Coast Camp were for the most part not harmed by the fire, and some species – such as the song sparrow and the American goldfinch – have flourished, said Geoffrey Geupel, a researcher with the Point Reyes Bird Observatory. In fact, the total songbird population has risen above pre-fire levels over the last two years with an increase in shrub cover and vegetation.
However, the numbers of individual tree-nesting species such as the Pacific slope flycatcher and the Swanson’s thrush have declined since the fire.
Overall, Geupel concluded that prescribed burning in the park "could benefit most bird species."
• The Bishop pine forest is reestablishing itself successfully, largely because several species of subterranean fungi which the trees rely on for proper growth increased dramatically after the fire, reported Thomas Bruns, a professor in Plant and Microbial Biology at UC Berkeley.
Bishop pines require the presence of various fungi which interact with the trees’ root systems, Bruns explained. Called "mycorrhizal" fungi, these organisms provide the tree with mineral nutrients in exchange for sugars.
Roughly 30 species of fungi inhabited the roots of the Inverness Ridge Bishop pines before the fire. While most of the larger "mushrooming" species, such as chanterelles, died in the extreme heat, other sub-surface, truffle-forming fungi increased in numbers to fill the void and have allowed new tree seedlings to flourish.
The ridge is being recolonized by a relatively high number of Bishop pine seedlings, explained Barbara Holzman of the San Francisco State geography department.
Bishop pines produce closed pine cones that typically require fire to open up and disperse seed. In studying the area in 1996 and 1997, Holzman found seedling density in the area two years after the fire was greater than the established tree cover, with roughly 11 seedlings per square meter. Studies found a growing diversity of plant species in the Bishop Pine area as time elapsed, with a significant increase in huckleberry (Vaccinium ovatum).
• The Muddy Hollow watershed, which drains into Limantour Estero, has experienced widescale erosion, reported Laurel Collins, a researcher with the San Francisco Estuary Institute.
Because of the lack of groundcover in the area, a network of small channels developed in many exposed surfaces during the winter after the blaze, Collins said. Subsequent wet winters eroded the highlands dramatically and deposited large amounts of sediment downstream in Muddy Hollow Creek.
The sediment load – roughly twice the usual – caused the creek channel to widen significantly and gradually move up the watershed, where hundreds of creekside alder trees were downed. Sediment deposited in the middle and lower regions of the watershed has allowed new alders to establish themselves, Collins said.
• A greater diversity of plant species has been found in the burned areas of coastal scrub than in similar unburned areas, said Amy David of San Francisco State University.
In May 1996, only seven months after the fire, David observed a nearly 100-percent recovery in the vegetative groundlayer in the charred scrublands.
In studying 18 sites with varying degrees of fire damage, David discovered that after two years most of the cover in the scrub was composed of native species that had existed there before the fire. The fire especially benefited the California lilac (Ceanothus thyrsisflorus) and lupine (Lupinus arboreus), two species which rely on seed dispersal to reproduce.
• Butterfly and moth populations have made a significant but still incomplete recovery, said Dr. Jerry Powell of UC Berkeley.
Powell had conducted daytime surveys from March through October each year and done limited sampling with blacklight traps. He has recorded about 355 species of Lepidoptera – the order of winged insects which includes butterflies and moths – or approximately 60- to 70- percent of the number estimated to inhabit the area before the fire.
Overall, Lepidoptera species reestablished themselves more quickly and successfully in the riparian woods and canyons lower on Inverness Ridge. The insects have been less successful in areas higher up, where the fire damage was more total.