Junction Sheep Range Provincial Park

Grassland Ecology

Grassland Plants: BC grasslands are characterized by low annual precipitation. Over many areas of this landscape, summer droughts are too severe for trees to become established. Consequently, grasses (principally bunchgrasses) form the dominant vegetative cover. Several drought tolerant shrubs such as big sagebrush and rabbitbrush, and other species such as prickly pear cactus are also common. Many grassland plants have evolved to thrive in this arid environment by completing their annual growth and reproduction cycles early in the growing season, and setting seed and entering dormancy before soil moisture is depleted. Many have also evolved extensive, fine root systems that are very efficient at capturing what little moisture is available. Others, such as big sagebrush, have roots that penetrate over 2 metres into the soil in order to capture water that is generally unavailable to most grasses and forbs. Many grassland plants are adversely affected by excessive grazing during the active growing season because nutrient reserves in their roots are at an annual minimum during this period.

Cryptogamic Crust: An interesting and ecologically significant feature of these arid natural grasslands is the occurrence of a thin, fragile, living, organic crust comprised of bacteria, algae, lichens, mosses, fungi, and liverworts. This crust occupies the soil surface between the grasses, forbs, and shrubs. This thin biotic layer, properly referred to as the microbiotic or cryptogamic crust, when fully developed may include 30 or more different species on any one site. Because these organisms are so small and inconspicuous, they are often overlooked. The cryptogamic crust is vital to grassland ecosystems, and several of its component species are rare or endangered.

Research has shown that cryptogamic crusts improve surface soil structure, water infiltration into the soil, and the soil's ability to retain water. The crust also reduces water and wind erosion by forming a spongy layer that binds the soil together. Several of the organisms in this crust are "nitrogen fixers"; these organisms are able to convert atmospheric nitrogen to a form that is more readily useable by plants. The crust also impedes the establishment of invasive weedy species and helps to preserve biological diversity by providing habitat and nutrients for a number of small plants and animals.

The cryptogamic crust is extremely fragile and sensitive to disturbance, especially during dry conditions. Trampling from humans, livestock and vehicle traffic can easily damage or destroy it. Research has shown that on many sites where the cryptogamic crust has been destroyed, it may take from a few to several decades for the crust to re-establish and recover to its original undisturbed condition.

Disturbance of the fragile cryptogamic crust may have lasting effects on the ecosystem as a whole. To protect these important and fragile ecosystems, please remain on designated roads and trails at all times.

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