The Importance of Browse Plants in Producing Large Herbivores on Western Native Rangelands

by C. Wayne Cook

 

Browse plants are the most adaptable group of forage species inhabiting the rangelands of the western United States. There is great variability in sites where these plants are located with respect to soil types, topographic features and environmental characteristics. This assortment of site conditions hosts a large array of browse species. It is important to emphasize the importance of browse plants as a food source to both native and domestic range animals in the western rangeland ecosystems.

Harshberger who has spent much time in accounting for the shrub formations in the western United States has stated that more then 30 recognized shrub formations have been identified in the western United States but many are too complex in their content of species and species variation for identification of a formation.

Habitat Factors of Browse Forage Species

The browse types are not small in area but rather occupy many thousands of acres of rangeland along the fringes of large forest types throughout the western range areas of the United States. It has been stated by many authors that perhaps as many as 500 to 600 species of browse species occur in the western rangeland area of the United States. Many of these areas are subject to great aridity, coolness, evaporation, and alkalinity that will not support tree growth.

In general, both domestic and wildlife animals readily eat the more succulent browse species. There are browse species with larger and coarser leaves that are rather unpalatable. In those cases both leaves and stems go uneaten by livestock and wildlife.

It should also be mentioned that a great many rangeland browse species contain rather large quantities of essential oils, resins and waxes that appear in chemical analysis to represent digestible energy in the plants. But in fact, these oils, waxes and resins are eliminated from the animals' body through the urinary tract and are lost as energy sources to the animal.

Season of Use and Forage Sources on Native Rangelands

In comparing the importance of trees, forbs, browse, and grasses we must evaluate the importance of seasons of use that are associated with each of the forage types.
The small woody species that retain their foliage during the winter and are readily eaten during this season represent a very important source of nutrients in the fall and winter seasons. These woody species allow for economical year long grazing of domestic animals and also enable wildlife animals to exist all year on native rangelands. This fact about smaller woody browse is an important consideration in managing energy in the native plants for maximum export of saleable material from rangeland ecosystems.

Let it be recognized that the evergreen browse species are the most reasonable means of furnishing energy to animals in the ecosystem for year long sustenance on the native rangelands of today.

Quantity of Browse in Western States

Under forest trees, in open areas within forest types, and in the broad browse types that cover almost 1/4 the area of some western states we perhaps have the largest native range of browse in the world. For instance, the entire area of the tall grasses from Texas to Canada have many expressions of the browse vegetation types interspersed with the grasses each reflecting the differences in the broader ecoclimate zones. This can be said of each broad browse formation found in the 11 western range states. These variable browse types are expressed in topographic features such as draws, north and south slopes as well as east and west slopes along drainages. For the most part, the different directional slopes display a unique array of browse and grass species. Some browse species are abundant on one slope and sparse on another or sometimes entirely missing on one directional slope and abundant on the other directional slope across the draw on the other side.

It is apparent that shrubs or browse have no specific ecological niche. The term "browse" means that animals consume these plants by mining or cropping the plants in r small and selective bites. Browse types can be the most important and the most wide spread of any range forge type in the western range area of the United States. The author has witnessed the ever present growth of browse on the various topographical features of each western state.

Eventhough browse is present throughout the 11 western states in relatively small patches that are natural, these areas are not given a "formation" classification or even a patch acknowledgment. Maybe the reason for this is that the many and variable species present do not display a common presence that links them together. In any event, they have a nomenclature of stature known as "browse". Thus it is seen that there is not a scientific nomenclature to bring these vegetation types to the forefront for recognition by scientists.

Dayton states that western shrubs (browse) are environmentally varied in their distribution being found from the seashore along the west coast to the timberline in the mountains of the western rangeland states. Browse endures in very arid sites and on sites where water is intermittently plentiful along bogs. Very few forms of plant life will endure greater alkalinity or salinity than certain browse plants.

To show the author's bias he wishes to state that "BROWSE" is the largest range forage type and one of the best rangeland nutritional types in western North America. It is found intermixed with most of the prominent rangeland types. It's versatility is expressed in site location, nutrition,and palatability. And overall browse production can be considered outstanding because of its varied and frequent presence, nutrient content, and stability.

At best only a few of the browse types could be placed on a rangeland forage type map because of the many small dots or smears that would be required. Botanical composition changes by sites always suggests a mixture of species by moisture. Increased browse presence on swales and slopes suggests a prominent change in botanical composition.

It is not possible to give a measured average of the acreage of shrubs in the western range area in the western range states but Dayton suggests that it is in the nine digits at least (100,000,000) acres. Rangeland managers cannot overlook the value of browse plants in the health and nutritional value of their ranges.