Inyo National Forest Research Articles

Valuing the impacts of forest disturbances on ecosystem services: An examination of recreation and climate regulation services in U.S. national forests

The increasing frequency and severity of forest disturbances challenge the sustainable provision of ecosystem services by forests, and this is true even in regions with net forest growth. The combination of ecosystem service losses from forest disturbances that are immediate as well as the slower post-disturbance process of forest regrowth could result in long-lasting social, economic, and environmental costs. Using economic and geospatial analysis, we estimate the value of recreational services losses due to drought and quantify the social cost of carbon emissions due to wildfires and bark beetle damage in three National Forests in the Sierra Nevada region, California (Inyo National Forest, Tahoe National Forest, and Lake Tahoe Basin Management Unit). Our findings indicate that recent droughts resulted in an annual reduction of about $73 million, $36 million, and $15 million for Lake Tahoe Basin Management Unit, Tahoe, and Inyo National Forests, respectively. Tree biomass loss due to wildfires and bark beetle damage generated around 10 Mt CO2 of total emissions from 2003 and 2012. The estimated cumulative social costs of such emissions were around $0.8 million for fire and $2.4 million for bark beetle (using a 3% discount rate for related climate change damage). The social costs almost tripled under extreme climate damage projections. Our analysis could inform adaptation and management strategies to conserve or enhance the health and function of publicly managed forests, and to protect their flow of ecosystem services for present and future generations.

Finding Methuselah: New Light on an Old Story

Edmund Schulman is rightly honored for quantifying the age of bristlecone pines and discovering individuals significantly older than giant sequoias (Sequoiadendron gigantea), previously thought to be the oldest living things. However, George Engelmann inferred the potential for great age in his description of bristlecone pine (Pinus aristata) almost a century before, in 1863. Staff from Inyo National Forest re-made Engelmann's inference, and publically asserted that White Mountain bristlecones might outlive giant sequoias before Schulman had published any results of his bristlecone research.Schulman sampled White Mountains pines after seeing a photograph and caption associated with an article by founders of the University of California White Mountain Research Station. Although Schulman's correspondence and publications make this clear, incorrect theories regarding his decision to come to the White Mountains have been published and are promulgated at the Schulman Grove Visitor Center in the White Mountains. This paper places Schulman's work in its historic context by recovering forgotten information about attempts by Inyo National Forest staff and White Mountain Research Station to call attention to the trees. It also recovers details of Schulman's and C. Wesley Ferguson's activities in the White Mountains range as documented in field notes and Thomas Harlan's Bristlecone Pine Project database.

Bristlecone, Limber Pine Geology, and Soil Substrates

Bristlecone Pines are among the oldest living trees in the world, and the climate condition under which they thrive is nothing short of extreme in the alpine zone. The experiment takes place in Inyo National Forest, where a hundred Bristlecone and Limber Pines were assessed. The trees were chosen based on a randomized selection that allowed us to analyze trees going upslope. We identified the rock type under the tree canopy, and analyzed the soil by taking the pH using a pH meter. By analyzing the rock and soil under the canopy of Bristlecone and Limber Pines we found that the soil conditions weren’t consistent with the favorable conditions under which the trees grow in. Climate change may play a role in the neutral shift in soil pH due to the increase in the rate of erosion of the rock type which is most prevalent among the pines, dolomite.

Habitat Suitability as a Limiting Factor for Establishment in a Narrow Endemic:Abronia alpina(Nyctaginaceae)

Abstract. Understanding the causes of narrow endemism is crucial to conservation, particularly in biodiversity hotspots like the California Floristic Province. The loss of rare species as a consequence of climate change could result in substantial reductions in biodiversity, especially in high-elevation systems. We investigated causes of range restriction by using the narrow alpine endemic Abronia alpina (Ramshaw Meadows sand verbena) as a case study. This study examined habitat suitability as a limiting factor for the establishment of Abronia alpina, an endemic native to only 2 meadow systems in the Sierra Nevada Mountains, Inyo National Forest, California, USA. We tested habitat suitability by (a) using vegetation community composition and diversity as a proxy; (b) measuring key physical environmental characteristics (i.e., soil moisture, pH, soil texture, and surface soil temperature); and (c) establishing experimental field and greenhouse germination tests that exposed seeds to soils from several pote...

Montane meadow plant community response to livestock grazing.

We examined long-term (10years) meadow plant community responses to (1) livestock grazing under riparian grazing utilization limits; (2) suspension of livestock grazing; and (3) meadow site wetness and precipitation on the Inyo National Forest, California. Observed trends in meadow plant species richness, diversity, and frequency of soil stabilizing species were not significantly different between grazed (N=16) and non-grazed (N=9) study sites (P>0.12 in all cases). Modest increases in richness and diversity were observed over the study period, but frequency of soil stabilizing species was constant. These results suggest that riparian conservation grazing strategies implemented during the study period neither degraded nor hampered recovery of meadow plant community conditions relative to non-grazed conditions. Meadow site wetness was negatively correlated to richness (P<0.01) and diversity (P<0.01), but was positively correlated to soil stabilization (P=0.02). Precipitation was not a significant predictor for plant community responses.

Natural forest floor clearings around trees in Jeffrey pine forests reduce tree damage and mortality following wildfire

In the western United States, trees in pine-dominated forests historically characterized by frequent, low severity wildfires often support deep litter and duff accumulations due to the fire exclusion policies of the last century. These accumulations at the bases of trees can smolder for long periods of time after the passage of fire, which can result in high temperatures, cambial injury, and subsequent tree mortality. As a result, prescribed fire prescriptions often call for the manual removal of litter and duff from the bases of large trees by raking or other means before fire is applied. Here we report on the presence of naturally formed, circular clearings in the soil surface litter layer that occur around the bases of tree boles in seasonally dry forests dominated by Pinus jeffreyi (Jeffrey pine) in eastern California and Baja California (along the eastern edge of the North American Mediterranean-climate zone). We show that such clearings significantly reduce fire severity and tree mortality in surface fires. In the Lake Tahoe Basin (LTB) study area, Jeffrey pine individuals surrounded by clearings experienced much lower bole char heights, and were 1/3 as likely to support crown torching as individuals lacking the clearings; mortality of Jeffrey pine lacking clearings was more than five times higher than individuals surrounded by clearings. Clearings also reduced mortality in incense cedar and white fir. Data from both the LTB and Inyo National Forest (INF) study areas show that clearings are larger and much more common in forests that have recently burned at low severity. In both locations, natural clearings around trees were about four times more common, and existing clearings about three times wider, in recently burned versus long unburned (>60years) sites. Logistic regression models show that clearing size, specifically the percentage of tree bole surrounded by a clearing, is an important predictor of Jeffrey pine survivorship in low to moderate severity fires, but clearing measures have never been included in previously published assessments of tree survival. We suggest that these previously unreported clearings are important features of Jeffrey pine and related semiarid forests and we recommend that more in-depth studies be made of their occurrence, formation, and ecological relationships.

Comment on “Has fire suppression increased the amount of carbon stored in western U.S. forests?” by A. W. Fellows and M. L. Goulden

Comment on “Has fire suppression increased the amount of carbon stored in western U.S. forests?” by A. W. Fellows and M. L. Goulden

Monitoring for potential effects of climate change on the vegetation of two alpine meadows in the White Mountains of California, USA

East Shield (3658 m) and Barcroft Gate (3697 m) Meadows in the White Mountains of California on the Inyo National Forest were selected for a pilot baseline monitoring study over five-year intervals to determine potential effects of future climate change on the meadows. Stated as a hypothesis: given the natural range of temporal variability of meadow vegetation, a significant portion of that variability is attributed to the effects of climatic variation. The study is associated with the Global Observation Research Initiative in Alpine Environments Project (GLORIA) hosted by the University of California White Mountain Research Station. Both meadows are sedge–rush–grass wet meadows, or fens, which are sustained by surface water in the form of streams and springs. A comprehensive plant list was compiled and the plant species of each meadow were sampled by a point intercept method along two randomly placed transects. The occurrence of all species at predetermined one-meter interval sample points along the transects were recorded, percent occurrence was calculated, and descriptive statistics were done. The monitoring objective is to detect a 20% biologically meaningful change in the vegetation over time with 90% confidence, and accept a 10% chance of a false change error (Type 1 error). Monitoring is planned to be done in conjunction with tracking change in precipitation and temperature. Three indicators of possible climate change were chosen. One indicator is increase in the abundance of those species whose upper range is at or below meadow elevations. The rationale for this indicator is based the 2007 IPCC report estimation that a doubling of atmospheric CO 2 will increase global temperature with a best estimate of +3.0 °C. Assuming that the present general lapse rate of −6.32 °C per kilometer for the White Mountains will persist, a 3.0 °C increase may result in an equivalent elevation of the meadows of about +475 m. Published elevation ranges indicate that most recorded species are not likely to be affected by the estimated temperature increase. Second and third indicators are a shift in cover from wet meadow to dry meadow species, and the presence and increase of shrub species resulting from postulated reduced precipitation with drying of meadows and encroachment by surrounding shrubs (sagebrush and rabbitbrush). This monitoring study has the potential to detect long-term responses of vegetation to climate change, and reduce uncertainties and confirm or correct the expected consequences of temperature change.

Effects of young Artemisia rothrockii shrubs on soil moisture, soil nitrogen cycling, and resident herbs

AbstractQuestions: How do young sagebrush shrubs (Artemisia rothrockii, Asteraceae) affect soil moisture availability? How do young sagebrush shrubs affect soil nitrogen cycling? How does the resident herb community respond to shrub removal in the early stages of sagebrush encroachment?Location: Mulkey and Bullfrog Meadows on the Kern Plateau in the Golden Trout Wilderness, Sierra Nevada Mountains, Inyo National Forest, Inyo County, California, USA.Methods: We removed young encroaching sagebrush shrubs from 3.5 m × 3.5 m plots and compared soil moisture, net mineralization, net nitrification, and herb cover with paired control plots over four growing seasons.Results: On average throughout the experiment, the difference between removal plots and control plots in soil moisture was small. Removal plots were wetter by 1.3 ± 2.0% at 0–30 cm depth, 2.1 ± 3.1% at 30–60 cm depth and 3.1 ± 5.8% at 60–90 cm depth. By contrast, after four years, net mineralization was 32 ± 26% (mean ± 95% CI) lower in sagebrush removal plots, suggesting that sagebrush encroachment increases rates of N‐cycling. Total herb cover was 13.0 ± 6.4% (mean ± 95% CI) higher in plots where young sagebrush shrubs were removed. This difference in cover appeared during the first season in which sagebrush shrubs were removed.Conclusions: Our results suggest that while young sagebrush shrubs do not contribute substantially to meadow drying, they alter N cycling rates, and may indirectly increase the rate of their own encroachment by competitively reducing resident herbs.

Computer Simulation as a Tool for Planning and Management of Visitor Use in Protected Natural Areas

The United Nations Environment Programme’s Principles on Implementation of Sustainable Tourism suggest that implementing sustainable tourism must include monitoring visitor use of protected natural areas and directing it to areas where the environmental and social impacts of tourism are minimised. Thus, sustainable tourism management requires information about the spatial and temporal flow of visitor use in protected natural areas to help identify potential tourism-related threats to the natural and cultural resources of an area and the quality of visitors’ experiences. Recent research has identified at least four ways in which simulation modelling of visitor use can facilitate more informed planning and management of sustainable tourism in protected natural areas, including (1) describing existing visitor use flows; (2) monitoring the condition of ‘hard to measure’ indicator variables; (3) testing the effectiveness of alternative visitor use management practices; and (4) guiding the design of research on public attitudes. The purpose of this paper is to demonstrate, using findings from studies conducted in the Inyo National Forest and Isle Royale National Park, USA, each of these four potential contributions of computer simulation to sustainable tourism management and planning. The paper concludes with an assessment of the limitations of existing applications of computer simulation to nature-based tourism and recommendations for future research.

California Lomatiums, Part VI. Composition of the Essential Oils of Lomatium foeniculaceum ssp. fimbriatu

The fruit essential oil of Lomatium foeniculaceum ssp. fmbriatum collected from the Inyo National Forest in California contained myrcene (24.5%), β-phellandrene/limonene (12.9%), germacrene D (13.9%), (E)-β-ocimene (10.4%), and (Z)-ligustilide (9.8%) as the major components. Germacrene D and (Z)-ligustilide also constituted the major components of the stem and leaf oil. (Z)-Falcarinol (38.1%) was the major component of the root essential oil.

The Postmortem Fate of Pat Gregory: A Disinterred Native American

In late June 1990, the Mono County Sheriffs Department in Bridgeport, CA contacted the Physical Anthropology Human Identification Laboratory (PAHIL) at California State University, Chico to seek assistance in the identification of a recently discovered skull. To assist with possible identification, the cranium received a classic physical anthropological/morphological analysis to suggest the decedent's sex, age at death, ancestral affiliation, and uniqueness. It was concluded the cranium was that of an older male, and someone with mixed ancestry, probably Native American/White. Suggested uniquenesses were an eroded and greasy texture, with adhering white sand, evidence of healed antemortem nasal fractures, and a bifid left occipital condyle. The cranium was confiscated from a man suspected of vandalizing a Native American cemetery just south of the community of Lee Vining. The cemetery was established in the mid-1800's by local Native American tribes. Although ownership of the land was disputed by the US Forest Service (the Inyo National Forest), and the Los Angeles Department of Water and Power (LADWP), county authorities claimed that because the incident involved the desecration of a cemetery and human remains, it was a legal issue, and therefore, the Sheriff's Department had jurisdiction over the case if not the land. The suspect pled guilty to the possession of Native American remains but claimed not to have desecrated a grave. Over the next year and a half, members of the Native American community representing various tribes sought the return of the cranium, while also seeking assurance that it belonged to the vandalized grave. While county, US Forest Service, and LADWP officials continued to argue over whom had jurisdiction of the remains the superior court judge ordered the county to pay for any analysis necessary to determine if the cranium belonged to the decedent in question. This report addresses the conclusions of that analysis and the disposition of the case. Furthermore, the report addresses the forensic value to Native Americans of the continued study of a wide variety of human skeletal remains.

Carex tiogana (Cyperaceae), a New Sedge from the Sierra Nevada, California

Carex tiogana is described as a new species in section Capillares from the Sierra Nevada, California, similar to C. capillaris but with culms usually shorter than or equal to the leaves, serrulate leaf midribs, conspicuous riblike veins on abaxial leaf surfaces, no enlarged vein at leaf margin, long prickles on leaf margins and pistillate scale midribs, perigynia fewer per spike and usually shorter, with longer prickles toward beak, usually shorter beaks, and shorter achenes. A diminutive plant belonging to Carex sect. Capillares Ascherson & K. Graebner was discovered in the Tioga Pass region on the eastern border of Yosemite National Park, Mono County, California. No member of section Capillares has previously been reported from California (Mackenzie, 1922; Howell, 1959). The section includes two species known to occur in North America: Carex capillaris L. and C. williamsii Britton (Mackenzie, 1931-1935: 295297). Carex williamsii is known only from calcareous substrates in the high Arctic, while C. capillaris is a widely distributed circumboreal plant often subdivided into a number of infraspecific taxa or segregate species on the basis of growth habit, leaf width, the sex of flowers in the terminal spike, spike length, and perigynium size (Packer, 1983; Porsild & Cody, 1980; Scoggan, 1978; Polunin, 1943; Komarov, 1935). These segregate taxa, here treated as subspecies, are C. capillaris subsp. chlorostachys (Steven) Love, Love & Raymond, C. capillaris subsp. krausei (Boeckler) Bocher, and C. capillaris subsp. porsildiana (Polunin) Bocher. Carex tiogana D. Taylor & J. Mastrogiuseppe, sp. nov. [sect. Capillares]. TYPE: U.S.A. California: Mono County, headwaters of Parker Creek drainage, Mono Basin, along trail between Parker Pass and Koip Pass, Inyo National Forest (37049'28N, 119011'25W), 3260 m, 17 July 1988, D. W Taylor & KIC A. Teare 9981 (holotype, UC; isotypes, COLO, NY, US). Figure 1. Planta cespitosa; folia longiora culmis vel aequa, arcuata vel falcata, crassa, nervata abaxialiter, margines foliorum serrulatae, 8-12 aculei per mm, aculeus 0.1-0.14 mm longus, costa abaxialis serrulata. Squamae feminae costae serrulatae, 7-15 aculei per mm. Periginia 2-5(-8) per spicam, (1.2-)1.3-1.8(-1.9) mm longa, binervata, nervi serrulati versus rostrum, aculei 6-15, aculeus 0.05-0.2 mm longus; rostrum (0.1-)0.3-0.5(-0.7) mm longum ad achenium. Achenia 0.8-1.1 mm longa. Perennial, densely caespitose in small clumps. Culms 1.7-6(-7.3) cm, shorter than or about equaling the leaves (occasionally slightly longer). Leaves generally clustered on the lower one-quarter of the culm, blades thick, stiff, bright green, arching to falcate, channeled along the midrib, (1.3-)1.7-6.5 cm X 0.9-2.2(-3) mm, with 3-5 prominent veins abaxially but without thick vein at margin, margins and midrib with 8-12 stiff prickles per mm, prickles 0.1-0.14 mm long. Inflorescence bracts with sheath 3-5 mm long, blade 4-26 mm long. Terminal spike staminate, 5-8 mm long; staminate scales straw-colored with yellow serrulate midrib. Pistillate spikes usually 2 or 3, 3-5(-7) mm long, on slender + nodding peduncles 8-11 mm long; pistillate scales ovate, shorter and wider than perigynia, white-hyaline with green midrib, the apex rounded or with a short-apiculate extension of the midrib, midrib of at least some lower scales bearing 7-15 prickles per mm (0.025-)0.5-0.7 mm long, scales deciduous as perigynia mature. Perigynia (2-)5-8 per spike, obovate, (1.2-)1.3-1.8(-1.9) X (0.4-)0.7-0.9 mm, trigonous, glossy, body green to brown (chestnut), with usually two yellow-green ribs bearing 6-15 prickles toward the beak, prickles 0.05-0.2 mm long; beak (0.1-)0.3-0.5(-0.7) mm from tip to achene. Achene trigonous, 0.8-1.1 X 0.4-0.8 mm, filling perigynium body; stigmas 3. The plants are more vigorous when garden-grown (in Berkeley, California, and Moscow, Idaho) but are still small with culms shorter than to somewhat longer than the leaves and retain the other characteristic features (Table 1). NovoN 9: 120-123. 1999. This content downloaded from 207.46.13.151 on Wed, 28 Sep 2016 05:56:49 UTC All use subject to http://about.jstor.org/terms Volume 9, Number 1 1999 Taylor & Mastrogiuseppe Carex tiogana from California 121

Endoparasite infection and Cryptosporidium/Giardia in feral horses on public lands

Summary Two populations of feral horses and one population of domestic horses located in portions of eastern California and western Nevada (Inyo National Forest) were examined for the occurrence of endoparasite infection and the protozoans, Cryptosporidium parvum and Giardia duodenalis . The two groups of feral horses consisted of 24 sedentary horses and 29 nomadic horses; there were a total of 11 domestic horses. The sedentary and nomadic horses were tracked and observed for one to three days, respectively. Fresh fecal samples were collected from the respective groups and examined for parasite eggs using the Cornell-Wisconsin Centrifugal Flotation Technique. A total of 58 fecal samples were collected from the three groups (sedentary, n=16; nomadic, n=31; domestic, n=11). Data (eggs·g −1 ) were initially analyzed using the Kruskal-Wallis nonparametric statistical method. Mean separation was accomplished by using the Mann-Whitney U-test following an observed significant effect of group (p −1 for the sedentary, nomadic and domestic groups were 803.0, 69.0 and 321.0, respectively. The interquartile range along with the 25th and 75th percentile for the respective groups were 776.0 (332.0–1108.0), 136.5 (32.0–168.5) and 486.0 (198.0–684.0). The eggs·g −1 for the nomadic group were less than the sedentary horses (p −1 observed for the nomadic group is most likely due to the reduced time spent on the collection site relative to their movement pattern. Separate aliquots of the fecal samples were also analyzed for Cryptosporidium parvum and Giardia duodenalis . All fecal samples were negative for these two organisms.

Livestock grazing and habitat for a threatened species: Land-use decisions under scientific uncertainty in the White Mountains, California, USA

The North Fork of Cottonwood Creek, in the White Mountains, Inyo National Forest, California, is a critically important refuge for the Paiute cutthroat trout (Oncorhynchus clarki seleniris), a federally listed threatened species. Habitat for these fish appears to be limited by excessive levels of fine sediment in the channel, and livestock grazing of riparian meadows has been implicated in delivery of sediment to the channel. However, the relationships between land use and sediment yield have not been conclusively determined, in large part because there are no historically ungrazed sites to serve as long-term controls. Accordingly, land-use decisions must be made under scientific uncertainty. To reduce erosion and sedimentation in the stream, the Forest Service spent approximately US$260,000 from 1981 to 1991 to repair watershed damage from livestock grazing, prevent livestock from traversing steep banks, and limit livestock access to the channel. Throughout this period, livestock grazing has continued on these lands, yielding less than $12,000 in grazing fees. In revising its Allotment Management Plan for the basin, the Forest Service rejected the “no-grazing” alternative because it was inconsistent with its Land and Resource Management Plan, which specifies there is to be no net reduction of grazing.

Approach to geologic hazard zoning for regional planning, Inyo National Forest, California and Nevada : Seeley, M W; West, D O Bull Assoc Engng GeolV27, N1, Feb 1990, P23–35

Approach to geologic hazard zoning for regional planning, Inyo National Forest, California and Nevada : Seeley, M W; West, D O Bull Assoc Engng GeolV27, N1, Feb 1990, P23–35

Approach to Geologic Hazard Zoning for Regional Planning, Inyo National Forest, California and Nevada

The Inyo National Forest (the Forest), which occupies 3,000 mi 2 (7,770 km 2 ) in eastern California and western Nevada, is adminstered by the U.S. Forest Service (USFS). The uses of this national forest are primarily recreational, and as population in the region increases, the Forest will experience more intense use. This results in the need for additional roads, trails, camp-grounds and related facilities within the Forest. The most recent episode of strong earthquake activity occurred between 1978 and 1981, and caused an estimated $1.5 million in damage in the Forest area. In addition, seismically induced rockfalls caused at least nine injuries in and near the Forest. This earthquake activity and subsequent volcanologic studies were an impetus for the USFS to commission an evaluation and zoning of geologic hazards within the Forest for the purpose of land-use planning. The geologic hazards evaluated and zoned were limited to seismic hazards, slope instability, and volcanic hazards. Methods used included air-photo interpretation, literature review, consultation with selected geologists and volcanologists, and limited field reconnaissance. The study resulted in compilation of separate geologic hazard zoning maps at a scale of 1:24,000 for the three categories of hazards (seismic, slope instability, volcanic). The study concluded that slope hazards are of the greatest importance; seismic hazards are of moderate importance; and volcanic hazards are of the least relative importance. The hazard zoning maps and the accompanying report are now being used by the U.S. Forest Service planners for siting new facilities in lower risk areas, and for risk management.

Establishing Administrative "Standing": The Sierra Club and the Forest Service, 1897-1956

and Mono Craters are exceptions. They constitute high plateau, alpine country marked by hot springs, waterfalls, glacial moraines, volcanic cones, patches of rare red snow, floating pumice blocks, and glass-like lava flows. Irrigated by western rains and glacial waters these areas, shadowed by the mountains, once held delicate stands of slow-growing lodgepole pine, red fir, and Jeffrey pine-some 400 years old--while the sunny meadows regularly bloomed with purple lupin, Indian paintbrush, blue iris, shooting stars, and an occasional snow plant.' One of these oases was located along Deadman Creek in the Inyo National Forest. In the 1950s the U.S. Forest Service began logging the Deadman area, sparking a

Paleolimnological reconstruction of recent acidity changes in four Sierra Nevada lakes

We have completed a paleolimnological analysis of sediment cores from four lakes in the Sierra Nevada Range of California (USA). The diatom-inferred pH profile from Harriet Lake in Yosemite National Park (present pH=6.52) indicates no significant trends over the last 250 years. Inferred pH from Emerald Lake in Sequoia National Park (present pH=6.10) indicates a very small increase (<0.1 pH unit) over the past 60 years and perhaps another small increase (ca. 0.15 pH unit) since 1976. Eastern Brook Lake in Inyo National Forest (present pH=7.06) shows evidence of both long-term alkalinification (ca. 0.3 pH unit over the last 200 years) and pH fluctuations since 1970. Lake 45 in King's Canyon National Park (present pH=5.16) appears to have acidified slightly (ca. 0.2 pH unit) over the last 60 years. Factors causing the observed trends are uncertain, but a role for acidic deposition cannot be ruled out.

Long-Term Persistence of the Nuclear Polyhedrosis Virus of the Douglas-Fir Tussock Moth, Orgyia pseudotsugata (Lepidoptera: Lymantriidae), in Forest Soil

The long-term persistence of the nuclear polyhedrosis virus of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in forest soil has been established by bioassaying soil and duff samples from an area in which the last tussock moth outbreak took place in 1936–38. Samples were taken from beneath each of 75 white fir, Abies concolor (Gord. and Glend.) Lindl., trees selected within 17 clusters in a study area in the Inyo National Forest, California. Virus was present in 15 soil samples from 9 of the clusters. Although present concentrations of active virus are low (<45 PIB/cm3), enough remains in the mineral soil from sheltered locations to infect tussock moth larvae. Absence of active nuclear polyhedrosis virus in the duff layers above the positive soil samples indicates the duff has accumulated since the last epizootic of tussock moth nuclear polyhedrosis.