Tranquille Ecological Reserve Overview: Physical and Biological

Posted April 5, 2000 | Categories : 29,Reports,Species List |


Preservation of representative ponderosa pine and Douglas-fir ecosystems in a prominent interior valley

Physical: This reserve, located on the north side of the Thompson River valley, has two distinct landforms. Its northeastern half consists of steep, gullied slopes which drop away sharply from the Red Plateau to the north. These have much exposed bedrock, talus and colluvial material; soils, where developed, are Regosols. Below this escarpment are gently sloping fans of colluvial materials derived from glacial till on which Chernozemic soils have developed. Exposure is to the south and southwest. The climate is characterized by cold winters, hot summers and little precipitation.

Biological: The reserve is largely forested although tree cover is sparse in many areas due to aridity and/or lack of soil. Small areas of treeless grassland occur along its lower fringe, some of which have been modified by cultivation. Remaining natural grasslands are dominated by big sage, Sandberg’s bluegrass and needle-and-thread grass. Most of the gently sloping part of the reserve is covered by a ponderosa pine-bluebunch wheatgrass community having a sparse shrub layer comprised mainly of rabbitbush and big sage. Above about the 760 m elevation, a Douglas-fir-ponderosa pine-bluebunch wheatgrass community is present. Here, bluebunch wheatgrass is still dominant in the herb layer but the clumps are smaller and more widely spaced.

Wildlife surveys have not been carried out, although two snakes (Western Rattlesnake and Gopher Snake) are known to occur, and the area provides important winter range for mule deer and bighorn sheep.



Western Rattlesnake- Blue listed
Gopher Snake,ssp. deserticola-Blue listed
Bighorn Sheep-Blue listed
dotted smartweed-Blue listed
Hudson Bay sedge-Blue listed
awned cyperus-Blue listed
The Dalles milk-vetch– red listed
trailing fleabane
western fairy-candelabra
slender plantain
grey horsebrush

Climate Change: Possible changes in both the forest and grassland communities. Projected drought and heat may favour the grassland ecosystems and encourage the northward and upward migration of the forest systems.

Forest health: Suppression of fires on the grasslands has altered the natural disturbance regime.

Non-native species:: Invasive species have been introduced


bluegrass, Sandberg’s (Poa secunda ssp. sandbergii)
cyperus, awned (Cyperus squarrosus)
Douglas-fir (Pseudotsuga menziesii)
fairy-candelabra, Western (Androsace occidentalis)
fleabane, trailing (Erigeron flagellaris var. flagellaris)
grass, needle-and-thread (Hesperostipa comata)
horsebrush, grey (Tetradymia canescens)

milk-vetch, The Dalles (Astragalus sclerocaruis)
pine, ponderosa (Pinus ponderosa)
plantain, slender (Plantago elongata)
rabbit-brush (Chrysothamnus sp.)

sagebrush, big (Artemesia tridentata)
sedge, Hudson Bay (Carex heleonastes)
smartweed, dotted (Polygonum puntatum)
wheatgrass, bluebunch (Pseudoroegneria spicata)


Deer, Mule (Odocoileus hemionus)
Rattlesnake, Western (Crotalus oreganus)
Sheep, Bighorn (Ovis canadensis)
Snake, Gopher (Pituophis catenifer ssp.deserticola)