Pre- and Post-settlement Stand Development of Woodland Ecosystems in Lincoln County, Nevada
AuthorBradley, Megan Lyn
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Pinyon-juniper woodlands in the Intermountain West have been increasing in both density and area since at least the late nineteenth century. The increases have been primarily attributed to changes in wildfire regimes, caused by fire suppression practices and the introduction of grazing animals. The primary objective of this research is to examine stand development at two study sites (Mount Irish and the Clover Mountains) of Lincoln County, Nevada, with particular emphasis on pre- and post-settlement conditions. Twelve plots (each with an area of 0.1 ha) were established at each site, ten of which were randomly located. All woody stems within the plot were measured, mapped and cored to determine tree age. Data and wood increment cores were also collected from gridpoints on a 175 m grid. Tree establishment age was determined by counting rings. Total basal area is 14.5 m2/ha at Mount Irish and 13.8 m2/ha at the Clover Mountains. Current tree density at the permanent plots at Mount Irish is 324 stems ha-1 and at the Clover Mountains is 342 stems ha-1. Historic density at Mount Irish was 151 stems ha-1 and at the Clover Mountains was 191 stems ha-1. Density of pinyon pine at both sites has more than doubled since Euro-American settlement. An increase in the survivorship of pinyon pine was observed at both sites, with peak survivorship occurring from 1900-1940 at Mount Irish and from 1930-1970 at the Clover Mountains. Stand age data from the gridpoints show that pre-settlement trees occur throughout each site, particularly at Mount Irish. Other studies in the Intermountain west have shown similar survivorship trends in pinyon-juniper woodlands.