Study Sites

About these sites

The sites for this study are emphatically NOT randomly chosen. Nor are they meant to be "representative" of their ecological "communities," "biomes," or "life zones." They were chosen along an elevational gradient – the I-80 corridor – with an eye toward generating the maximum amount of data for comparison within sites among years and within years among sites. The criteria that went into their selection (in no particular order) were: ease of access; diversity of habitats within the framework of a manageable day hike; diversity of species present; low probability of major land-use change; and availability of long-term data from one or more nearby weather stations. The sites are not "pristine," though, as usual, the high-elevation one (Castle Peak) has the fewest visible human impacts. Several sites are unusually rich, faunistically speaking—they have significantly more species than one would be likely to encounter anywhere nearby—and this seems to be largely a function of disturbance. Very few California butterflies are adapted to, let alone restricted to, broad expanses of closed-canopy forest. A site like Donner, traversed by roads and the Transcontinental Railroad, presents a "permanent" state of succession highly attractive to butterflies. To the extent that they are relatively open, these sites may be warmer and have a better-developed and richer understory than "climax" sites. These are butterfly-friendly conditions.

Site Name Elevation (meters) Number of Recorded Species and Subspecies County Site Characteristics

Suisun Marsh

0 - 1 60 Solano Tidally-influenced complex of brackish and freshwater marsh. Plants include halophytes, sedges, rushes, cattails, reeds, and herbaceous perennial composites.

Gates Canyon

190 - 600 78 Solano Inner Coast Range foothill canyon. Vegetation includes: Interior Live Oak woodland, Blue Oak woodland, chaparral, Gray Pine, and riparian forest of Cottonwood, Bigleaf Maple, and Alder.

Willow Slough


West Sacramento

9 58 Yolo Central Valley Floor. Dense riparian Cottonwood and Willow forest with Valley Oak and Ash.

North Sacramento

8 62 Sacramento Central Valley Floor. Valley Oak woodland; riparian Cottonwood and Willow; annual grassland.

Rancho Cordova

58 58 Sacramento Eastern edge of Central Valley. Interior Live Oak-Gray Pine woodland, Valley Oak-dominated riparian forest, and annual grassland.


850 - 1200 104 Nevada Sierra Foothills. Deep canyon with mixed serpentine and metasedimentary geology. Canyon Live Oak woodland with mesic mixed lower-montane forest including Douglas Fir, Incense Cedar, and Ponderosa Pine.

Lang Crossing

1500-1700 116 Nevada West-slope Sierra Nevada. Mosaic of xerophytic vegetation (Goldencup Oak and Manzanita) and moist slopes with mixed mesic forest (including Douglas Fir, Ponderosa Pine, and Sugar Pine); site also includes a large wet meadow with boggy areas.

Donner Pass

2000 - 2200 119 Nevada, Placer High Sierra. Montane communities with local subalpine elements; granite balds with herbs and low shrubs; mature Red Fir forest; large wet and dry meadow complex with a few boggy spots, fringing Willows and Mountain Alders.

Castle Peak

2400 - 2775 96 Nevada High Sierra. Subalpine and alpine vegetation; tree-line of Mountain Hemlock, Lodgepole Pine, Western Whitebark, and White Pine; persistent snow fields, boggy seeps, and wet meadows.

Sierra Valley

1500 93 Sierra East side of Sierra. Wet and dry meadows with Juniper-shrub steppe and irrigated alfalfa fields.