Stubble height as a tool for management of riparian areas

Stubble height, a measure of the herbaceous vegetation remaining after graz ing, has been widely used in recent years to gage the impacts of grazing us e in riparian areas. Stubble height is a short-term management guide that s hould only be applied to help attain long-term ecological objectives; it sh ould not be thought of as a long-term management objective. Maintaining a minimum stubble height helps preserve forage plant vigor, ret ain sufficient forage to reduce cattle browsing of willows (Salix spp.), st abilize sediments, indirectly limit streambank trampling, maintain cattle g ains, and provide an easily communicated management criterion. Based on lim ited specific research of riparian system response and on knowledge of the characteristics of how cattle graze, a 10-cm residual stubble height is rec ommended by the authors as a starting point for improved riparian grazing m anagement. Monitoring should then be conducted to determine if an adjustmen t is needed. In some situations, 7 cm or even less stubble height may provi de for adequate riparian ecosystem function, particularly when streambanks are dry and stable or possibly at high elevations where vegetation is natur ally of low stature. In other situations, 15-20 cm of stubble height may be required to reduce browsing of willows or limit trampling impact to vulner able streambanks. The recommended criterion would apply to streamside and n earby meadow sites with hydrophilic or potentially hydrophilic vegetation, but not directly to dry meadows or even to all wet meadows. Stubble height may have little application where the streambanks are stabilized by coarse substrates, or the channels are deeply incised. The effects of residual stubble height in riparian functions have received limited direct experimental examination. Consequently, much of the informat ion in this review was derived from studies indirectly related to the quest ions raised and, to some extent, from observations of experienced professio nals. The authors have identified areas of scientific investigation needed to improve our understanding of the effects of stubble height on riparian f unction and grazing management.