BUNCHGRASS ECOSYSTEMS AND THE EARLY CATTLE INDUSTRY
IN THE THOMPSON-OKANAGAN

BFACTORS EFFECTING THE GROWTH OF BUNCHGRASS


Grazing

As the above "Bunchgrass growth curve" indicates, the effect of grazing bunchgrass during the spring months or grazing too extensively during the growing season can seriously harm the plant's ability to store food for the future. This can cause a weakening of the plant and lead to its elimination from a range, especially when drought, hard winters or insect damage follow the seasons of overgrazing. However, if the rancher is able to graze his cattle lightly during the growing season by not overstocking the range or to move his cattle from range to range, bunchgrass can continue to be the dominant species in the range. Another deleterious effect of cattle grazing on bunch grasses is the breaking down of the lichens that grow between the grass bunches by the hooves of the cattle, thereby causing a more rapid evaporation of moisture from the surrounding soil.


Snow Cover

The amount of snowfall in an area indicates a better moisture regime and therefore encourages the growth of bunchgrasses. Not only that but the snow cover also keeps cattle off the land during winter months and decreases damage that can be done from overgrazing during the winter.


Soils

Since moisture content of the soil is an important factor in the growth of bunchgrass, sandy soils tend to be more conducive to growth because they allow deeper moisture penetration and reduce evaporation. The sandy soils in the Osoyoos and North Okanagan areas are more suitable for Needle-and-thread grass.

Fire

When fire destroys a grassland habitat, the greatest damage is done to the non-forage plants such as sagebrush. Bunchgrasses, with a much deeper root system, are much quicker to rejuvenate and occasional fires keep the ranges healthy. This fact was probably realized by the native people, who frequently started fires to push back the forest cover and to make the grasslands stay healthy for game and horses that used the grasslands for forage.

DETERMINING THE EXTENT OF THE BUNCHGRASS RANGES

Bunchgrasses once covered the entire valley bottoms and upland plateaus of the Thompson-Okanagan and were found at higher altitudes where the moisture regime was dry enough to support them and eliminate competition from other species. Today there are few areas where these grasses can be found in abundance, due to the effects of cultivation, construction and overgrazing. As this study will look at the historic uses of bunchgrass, particularly as it applied to cattle ranching, some method has to be established to determine the location and extent of these ranges at the beginning of European settlement in the region. Fortunately it is possible to establish where bunchgrass would have been found and, to a lesser extent, where it is still found in the Thompson-Okanagan.

In order to determine the extent of the bunchgrass ranges at the time the first Europeans entered into the Thompson-Okanagan region, it is necessary to examine the biogeoclimatic units which exist in the region and use them to establish the zones where, left undisturbed, bunchgrass would be found. Fortunately the Ministry of Forests Research Branch has prepared a map of "Biogeoclimatic Units of the Kamloops Forest Region" which can be used for this purpose. It is important to realize that bunchgrass exists in several species in the region and the requirements for bluebunch wheat grass are not the same as those for Rough fescue or Idaho fescue. Bunch grasses can therefore be found within different altitude and moisture zones, depending upon species. With this in mind, mapping the (potential) bunchgrass ranges in the Thompson-Okanagan can be based upon the different zones where bunchgrasses can be found more or less in abundance.


Consultation with Dennis A. Lloyd, a Research Ecologist with the Kamloops Forest Region of the Ministry of Forests, resulted in the establishment of the appropriate zones. The obvious zone in which bunchgrasses would be found is that labeled as "Bunchgrass". As might be expected, this zone is found in the "Very Dry Hot", "Very Dry Warm" climatic zones and at the lower altitudes. Bunchgrass is also found in conjunction with Ponderosa Pine and the biogeoclimatic zone labeled "Ponderosa Pine" was included in the mapping because of this common occurrence. There is yet a third series of zones in which bunchgrasses could be found. The "Interior Douglas Fir" zones occasionally have "grassland" phases where bunchgrasses are found. All of the above zones, subzones and phases were included in the base map of bunchgrass biogeoclimatic units from which the outline maps of the Thompson and Okanagan regions were prepared.





Bunchgrass and beef
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