Throughout the southwest, exotic and non-native plant species such as saltcedar (Tamarix ramosissima) and Russian olive (Elaeagnus angustifolia) have transformed the environment by competing for groundwater and dominating ecosystems formally occupied by native cottonwoods (Populus deltoids ssp.) and willow (Salix sp.). Saltcedar was introduced to the Middle Rio Grande riparian forest (bosque) to control flooding and to decrease soil erosion rates due to its deep root system and prolific growth rate. This transformation, along with channelization and commensurate reduction in over bank flooding, has not only changed the ecology, structure, and composition of riparian vegetative communities, but also greatly increased the severity and frequency of wildfires. Saltcedar and Russian olive both have the tendency to produce large masses of dead dry branches or stems because of high stem mortality rates. This downed wood is the fuel that creates the swift moving wildfires in the Middle Rio Grande bosque. These fires present a major threat to structures and communities living near the bosque and causes substantial damage to the bosque environment. A study to evaluate the effects of the removal of exotic fuels was initiated in 1999 by the Rocky Mountain Research Station of the USFS in collaboration with other local organizations. Saltcedar and other exotic fuels were removed in several sections in the Middle Rio Grande bosque using three different methods to limit re-growth. In addition to determining the effects of fire propagation, the fuel reduction study included a component to investigate the impact of fuel removal on shallow groundwater resources. To determine the impacts to shallow groundwater from the fuel reduction treatment, a series of 24 shallow monitoring wells were installed and instrumented with data loggers to measure water levels. These wells were located in three different blocks, stretching from Albuquerque to the Bosque del Apache National Wildlife Refuge. Diurnal groundwater fluctuations were analyzed from years 2003 and 2005 during summer and winter periods, and the variations at control sites (no fuel reduction) were compared with treatment sites where exotic vegetation was removed and treated with herbicide. The diurnal data showed variations between the study plots as well as seasonal variability. Overall, the average fluctuations from the summer control sites (-10.81 mm and 6.69 mm) were of greater magnitude or similar to the fluctuations from the treatment sites (- 9.98 mm and 7.58 mm). During the winter dormant season, the treatment sites (-2.89 mm and 2.58 mm) held higher average fluctuations when compared to the control sites (-1.20 mm and 0.79 mm). The results indicated there was a low impact on shallow groundwater from the removal of exotic species because of only slight differences in diurnal fluctuations between the control and treatment sites.
Middle Rio Grande bosque, wildfires, riparian forest, exotic fuel removal, fire propagation
Price, Lynda. "The Response of Shallow Groundwater Levels to Fuels Reduction in the Middle Rio Grande Bosque." (2008). http://digitalrepository.unm.edu/wr_sp/88