PARENT SESSION
Oral Session #48: Vegetation Change and Response.
Presiding: D. Zobel
Tuesday, August 6. 1:00 PM to 4:45 PM. Mesquite Room, Radisson.

Response of groundwater dependent vegetation to precipitation and rising water table following drought in Owens Valley, California.

MANNING, SARA^*,1, ¹ Inyo County Water Department, Bishop, CA

ABSTRACT- Hydrological manipulations are affecting native ecosystems worldwide. The Owens Valley, California, experienced a six-year drought during which the amount of water pumped and exported from the valley increased sharply. Consequently, water tables dropped below vegetation root zones in several native groundwater dependent plant communities, and perennial cover levels showed marked declines. During and following the drought, ground water levels and perennial cover were measured. The purpose of this study was to analyze the contribution of both precipitation and ground water to changes in perennial cover. Multiple regression was applied to data from areas that experienced a return of the water table to the root zone of the dominant plant species. Most of the variance in perennial cover in disturbed groundwater dependent plant communities was explained by groundwater fluctuation. Surprisingly, the response to rising water table overwhelmed the perennial cover response to precipitation. Furthermore, when these results were compared with data from regions of the valley not affected by pumping during the drought, it was found that perennial cover can be sustained during drought periods as long as the natural water table fluctuations are not altered. These results could be used to help better manage native ecosystems in places where water resources are being exploited.

KEY WORDS: water resources, phreatophyte, intermountain