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ERO Resources <br />3) reduotion in oompetition between grasses and juniper seedlings as <br />• the result of overgrazing; and <br />4) climatic shifts that favor woody species. <br />A fifth reason obtained from the current research is the removal of <br />topsoil areas, leaving rocky subsoils that fawr the germination and <br />establishment of juniper trees. <br />The role of sheep in increasing juniper on rangelands is documc+nted by <br />Miller (19211. Miller writes that sheep were the chief vector for the <br />spread of juniper seed. In his report Miller states that between 10,000 <br />and 15,000 acres of grassland have been "reforested" by sheep. <br />Support for the theory that juniper woodlands have increased since the <br />advent of grazing comes from dendrochronological studies in the <br />southwest. Nest et al. (1975) report that the maximum age of juniper <br />Lrees sampled exceeds 1,000 years. However, the age of 21 percent of <br />junipers sampled had less than 100 growth rings. Coupled with this <br />• information is the observation of the existence of relict areas that <br />demonstrate substantial numbers of dead shrubs that once occupied a <br />well-developed and perhaps dominant shrub understory or layer. The <br />existence of relict savannahs also strongly indicates a strong pattern of <br />succession involving juniper invasion. In these areas young junipers are <br />common, as has bean noted in the Deserado Mine Permit Area. In supporting <br />research Tausch et al. (1979) report that tree densities in woodlands have <br />increased and forage decreased over the last 50 to 70 years. <br />The autecological charges that have occurred as a result of increased <br />density of juniper on rangelands involves allelochemics, as well as niche <br />changes created by surface disturbance and erosion. Jameson 41966) <br />reports that the phenolic compounds present in juniper leaf litter are <br />highly irt~ibitory to grass growth. Jameson also indicates that the <br />accumulation of juniper litter may deleteriously affect decomposition and <br />mineralization processes essential for nutrient cycling. In addition, the <br />effects of juniper litter are long-lasting, remaining after removal of <br />• <br />II.F-14 <br />