CHAPTER 11 Northeastern Plateaus Bioregion GREGG M. RIEGEL, RICHARD F. MILLER, CARL N. SKINNER, AND SYDNEY E. SMITH The only means for taking deer wholesale was by kupi’t (firing) and was practiced in late summer, about the middle of August. When deer were sighted on a hill, a group of hunters hastened there, some on either side of the mountain. They started fires, working them around until the band was completely encircled. This accomplished the fires were brought closer, constricting the circle until the animals were bunched on the crest on a hill where they could be shot conveniently. Deer firing was ordinar- ily executed without undue noise, but if a bear were accidentally caught in the fire, a great hue and cry was set up to warn others and to inform them which direction the animal was headed. Fire use by Northern Paiute Indians, as told to ISABEL T. KELLY, 1932 Description of the Bioregion elevations, ranging from 1,204 m (3,950 ft) to 3,016 m (9,892 ft), can change quickly. The Pit River, with headwa- Northeastern California landscape is a mixture of vast arid ters in the Warner Mountains and, until 1877, Goose Lake, basins and uplands, and forested mountain ranges inter- traverses the Modoc Plateau from east to west where it enters spersed with both fresh water and alkaline wetlands. The the Cascade Range and flows into the Sacramento River entire bioregion is significantly influenced by the rain shadow (Pease 1965). The Modoc Plateau is also scattered with sea- effect of the Cascade Range to the west. Three ecological unit sonal ponds and pluvial lakebeds. Several rivers, including subsections are treated in this chapter: (1) Modoc Plateau Sec- the Susan, which drains into the Honey Lake basin, and the tion (M261G), (2) northwestern Basin and Range Section Carson and Walker in the northern Mono section, flow from (342B), and (3) extreme northern portion of the Mono Section west to east and transect the steppe. (341Dk). The Cascade Range defines the western edge of the Several vegetation zones occur in the Northeastern Plateaus Modoc Plateau, and the Sierra Nevada defines the western bioregion. The general sequence, from the lowest elevations boundary for the southern portion of the northwestern Basin to the highest, are: sagebrush steppe (includes Wyoming big and Range and Mono Sections. There is no one overriding fea- sagebrush and western juniper series zones), lower montane ture that cleanly depicts this bioregion to the north and east (ponderosa pine series zone), mid-montane (lower-elevation as the political borders of the states of Oregon and Nevada, white fir series zone), upper montane (upper-elevation white respectively, define the boundaries (Map 11.1). fir series), and subalpine (whitebark pine series zone). The bioregion as defined in this publication is too dry and cold to support red fir (Abies magnifica) and mountain hemlock Physical Geography (Tsuga mertensiana), and only a few Douglas-fir (Pseudotsuga The Northeastern Plateaus bioregion extends east of the menziesii) or sugar pines (Pinus lambertiana) are found on the southern Cascade Range and south along the east slopes of extreme western edge of this bioregion. Several species reach the Sierra Nevada. This region represents California’s portion the extent of their ranges in this area, as detailed below of the Great Basin. The climate is dry, cold, and continental. (Smith and Davidson 2003). Volcanism dominates the geology, topography, and geo- The volcanism that shaped the area is fairly recent, dating morphic processes of the area. The most conspicuous feature from the Pliocene to Pleistocene eras, and includes volcanic of the region is the Modoc Plateau, a high, flat terrain char- ash deposits, lava flows, talus jumbles, obsidian deposits, acterized by basalt plains and volcanic shields (MacDonald and lava rims. Soils that have weathered in place, particularly and Gay 1966). The topography is extremely abrupt and at the lowest elevations of the region, are often poorly 225 developed, shallow, and rocky. Clays weathered from basalt These are: (1) the Pre-Frontal Winds, (2) Lightning with Low are a typical soil texture component in many locations. River Precipitation, (3) Moist Monsoon, and (4) Strong Subsi- deposits include Mollisols and Aridisols, and lakebed deposits dence/Low Relative Humidity patterns. The pre-frontal and include silt, sandstones, and diatomite (Young et al. 1988). At subsidence patterns mostly affect fire behavior and spread, higher elevations in the bioregion, most residual soils are whereas the lightning with low precipitation and moist mon- Mollisols, often weathered from basalt parent materials. Soils soon patterns are important for their fire ignition potential. transported to lower-lying areas via alluvial processes are Pre-Frontal Winds often Vertisols. Soil temperature regimes are mesic, frigid, and Pre-frontal wind events are frequent in cryic, and soil moisture regimes are mostly xeric and aridic. springtime and again in late summer and fall. They are of most consequence in the latter period, when both live and dead fuel moistures are low. The pre-frontal weather pattern Climatic Patterns occurs in advance of spring or fall cold fronts, or upper low- Climate data in northeastern California is somewhat inac- pressure troughs. Tight pressure gradients aloft produce mod- curate because of historically few and somewhat widely erate to strong south to west winds, which can surface spaced long-term climate stations confounding the difficulty strongly on the lee side of the Cascade Range and Sierra in interpolating the marked rain shadow effects from topo- Nevada. As the downward-moving air masses lose elevation, graphic features. The PRISM climate model (Daly et al. 1994) they gain temperature and lose humidity due to adiabatic uses extrapolations from weather station data points, and if compression. These phenomena are combined with moder- Ϫ1 Ϫ1 the data are sparse then errors result in the extrapolations. In ate to strong wind speeds of 24 to 56 km h (15–35 mi h ), Ϫ1 Ϫ1 arid climates such as northeastern California, slight differ- with gusts as high as 80 km h (50 mi h ). This pattern usu- ences in precipitation and temperature show up in vegetation ally occurs between 5 and 10 times a year, with one or two expression more readily than in wetter climates, and current significant events during the fall season of most years. These climate models sometimes fail to predict this. We expect this conditions can lead to rapid fire spread and extreme fire will change in the next couple of decades as there are now behavior. more and spatially denser automated stations that should Lightning with Low Precipitation This weather pattern typ- result in better predictive climate, vegetation, and fire mod- ically affects northeastern California to varying degrees, once els. In the meantime, structured observations of vegetation or twice per fire season, although it can occur as many as four on zonal sites (sites reflecting the regional climate more than or five times in a single year. Though not a term generally rec- local topography or soils) are the best way to infer the climate ognized by meteorologists, local fire and resource mangers of this bioregion. use “dry lightning” to describe this pattern because it includes episodes of thunderstorms that are more likely to FIRE CLIMATE VARIABLES cause fires than others. The pattern is most common in The bioregion is buffered from Pacific storms by being in the July and August, but can occur from June through mid- rain shadow of the Cascade Range and Sierra Nevada. Most September. It sets up when the dominant high pressure aloft of the precipitation occurs between October and May; with becomes oriented from roughly northern Nevada down most occurring between November and April as snow. The through Arizona. When the main high-pressure center is in summer months from May to October are mostly rainless northern Nevada, it draws mid-level moisture northwest- with the exception of summer thunderstorms. Summer thun- ward, tracking along the western flank of the high-pressure derstorms can be locally significant and are the source of mass toward northern California. Often, this moisture trans- lightning ignitions. The range of annual precipitation in the port roughly parallels the Sierra Nevada, with the greatest Northeastern Plateaus bioregion is from 17.8 to 121.9 cm moisture from near the crest eastward. When relatively cool (7–48 in) (Daly et al. 1994). The overall bioregional average disturbances aloft are caught up in this larger-scale flow pat- is 43.2 cm (17 in). However, local orographic enhancement tern they can act as “triggers,” destabilizing the mid and boosts precipitation from 91.4 to 121.9 cm (36–48 in) in the upper layers enough to generate high-based thunderstorms. northern Warner Mountains. Temperatures range from Jan- Because the resulting cells have high bases, much of the pre- uary minimums of Ϫ11°C to Ϫ2°C (12°F–28°F) to July max- cipitation associated with them evaporates before reaching imums of 21°C to 32°C (69°F–89°F). The majority of fires the ground. The events usually result in many fire ignitions occur from June to September, and certain fire weather con- over a relatively short time, a situation that can be rapidly ditions can affect fire ignitions and fire behavior during those compounded by the gusty erratic downdraft winds associated months. with the thunderstorms (Rorig and Ferguson 1999, 2002). Moist Monsoon The moist monsoon pattern is the “true” WEATHER SYSTEMS southwestern monsoon, and it is rare in the Northeastern There are four basic fire weather patterns that can signifi- Plateaus and the rest of northern California. The pattern is cantly affect fire behavior and natural ignitions in north- characterized by unstable air masses, high humidity, and fairly eastern California during the May-to-October fire season.