Mancos Watershed Functional Assessment

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Table 1: Continued from the previous page. CATEGORY AND JUSTIFICATION FOR INCLUSION IN THE RSRA ASSESSMENT VARIABLE The amount, composition, distribution and condition of large woody debris (LWD) in the Large Fish/Aquatic Habitat: stream channel and along the banks provides important fish habitat for nursery cover, feeding, woody debris and protective cover. Streams with adequate LWD generally have greater habitat diversity, a natural meandering shape and greater resistance against high water events. Fish/Aquatic Habitat: Overhanging terrestrial vegetation is essential for fish production and survival, providing shade, Overbank cover and bank protection from high flows, sediment filtering, and input of organic matter. Overbank terrestrial invertebrate cover also is important for terrestrial insect input (drop) into streams, which is a key source of habitatfood for fish. High cover and structural diversity of riparian vegetation generally indicates healthy and Plant Riparian vegetation: productive plant communities, high plant species diversity and provides direct and secondary community cover and food resources, cover, and breeding habitat for wildlife. This affects avian breeding and structural diversity foraging patterns in particular. Good structural diversity can also reduce flood impacts along banks. The distribution of size and age classes of native dominant species indicates recruitment Riparian vegetation: success, ecosystem sustainability, and wildlife and fish habitat availability. When one or more Dominant shrub and tree age classes of the dominant species are missing, it indicates that something has interrupted the demography (recruitment natural process of reproduction and individual plant replacement. In time, this may lead to the and age distribution) complete loss of the species in the area as older individuals die off and are not replaced by younger plants. Non- Riparian vegetation: Non-native plant species profoundly influence ecosystem structure, productivity, habitat quality, native herbaceous and and processes (e.g., fire frequency, intensity). Strong dominance by non-native plants may woody plant cover eliminate key attributes of wildlife habitat quality, and may limit ungulate and livestock use. Riparian vegetation: Ungulate herbivores can affect riparian soils, ground cover, and general ecosystem condition. Mammalian herbivory Utilization levels >10% in riparian zones retard vegetation replacement and recovery. Moderate impacts on ground cover and higher levels of grazing almost always increase soil compaction and erosion. Riparian vegetation: Ungulate herbivores can affect recruitment of woody shrub and trees by clipping or browsing Mammalian herbivory the growing tips of the branches. Continued high levels of utilization lead to the death of the impacts on shrubs and plant and over time can cause the loss of all shrubs and trees in a local area. small trees Riparian shrubs and trees often grow in dense patches that provide food, thermal cover, predator protection and nesting or breeding habitat for terrestrial wildlife, including many invertebrates, Terrestrial Wildlife Habitat: amphibians, reptiles, birds and mammals. These patches are often absent in riparian areas that Riparian shrub and tree have been heavily utilized by livestock and other ungulates, or that have been damaged by other canopy cover and human activities. As a result, many native wildlife species may no longer be able to survive in connectivity the area. Patches of dense vegetation, both native and exotic, also plays a key role in trapping sediment during periods of over-bank flow. Natural processes create a diversity of fluvial landforms, including terraces, bars, oxbows, wet marshes and fluvial marshes, which provide habitats for different species of terrestrial wildlife. Terrestrial Wildlife Habitat: Conversely, in a highly degraded system with extensive erosion and downcutting, there may be Fluvial habitat diversity only a single fluvial form: a straight and single-depth channel and steep banks without vegetation. 14