Revegetation of Pinon-Juniper woodlands with Native Grasses

Chong, Geneva

In 1978 Earth Environmental Consultants, Inc. estimated that some regions in Bandelier National Monument in northcentral New Mexico, were experiencing erosional soil losses of O.Sm/lOOyrs- an unsustainable rate in an area where soil may only be O.Sm deep. The abnormally high rates of erosion are most likely the result of past land use and management practices which have reduced herbaceous groundcover and left large expanses of bare soil. Results from several ongoing s􀁲udies in the Pinon-Juniper Woodland at Bandelier National Monument indicate that, despite the protection to the land provided by the status of being a National Park, the downward trends in this ecosystem continue. Thus it appears that the eroded condition of the land cannot be improved rapidly enough to save the soil without active management. The studies included in this report are: 1) vegetation surveys from grazing exclosures established in 1975; 2) comparisons of herbaceous vegetation in tree interspaces vs canopied areas; 3) vegetation transects to determine percent cover by species and cover type (i.e. bare soil or cryptogam); and 4) a greenhouse experiment to study the effects of cryptogamic (microphytic) crusts on native grass seed germination. The results of these studies are respectively: 1) the removal of grazing pressure does not result in automatic increases of grasses and other herbaceous groundcover; 2) more herbaceous groundcover occurs in canopy interspaces suggesting that high tree densities may prevent establishment of herbaceous groundcover and thus increase erosion; 3) bare soil may be as high as 50% with vegetative cover as low as 10%, while cryptogamic crust cover may be as high as 30%; and 4) cryptogamic crusts may inhibit seed germination. Finally, a revegetation experiment which compares three tree thinning treatments and six seeding (native grasses) treatments is described, and results from one growing season are discussed. Results from the revegetation experiment will be used to treat selected areas in Bandelier National Monument and can be applied to similar ecosystems with similar erosion problems.