Evaluation of groundwater recharge and riparian vegetative succession using a post-fire chronosequence

Historically fires in the western United States burned more frequently than presently.  Western forests were more park-like compared to today’s dense stands that are considered to be unhealthy.  Scientists are recommending fire to reduce hazardous wildfires, improve forest structure and composition, improve habitat and increase watershed health.  Nevertheless, relatively little is known about the effects of fire on riparian plant communities.  Dense stands of vegetation have been shown to lower water tables resulting in loss of riparian vegetation.  Fire reduced vegetative density would likely promote riparian succession via groundwater recharge.  The purpose of this study is to investigate links between fire, groundwater recharge and riparian vegetative succession via a post-fire chronosequence.  Water wells, vegetation transects and weather stations have been used to monitor four to five intermittent and ephemeral streams at each of three different-aged wildfire sites on the Cibola National Forest, New Mexico.  Water table depths and vegetative cover are positively correlated with time since burn.  A principle components analysis suggests that depth to water table is highly associated with plant available soil moisture on the oldest burns and that a combination of plant available soil moisture and wind speed are associated with depth to water table on the youngest burns.  Soil texture and vegetation are significant factors determining plant available water and wind speed.  Results to date suggest that fire has the potential to alter principle factors determining depth to ground water, such as reducing vegetative cover and altering wind speed.