Monitoring for potential effects of climate change on the vegetation of two alpine meadows in the White Mountains of California, USA

Abstract

East Shield (3658 m) and Barcroft Gate (3697 m) Meadows in the White Mountains of California on the Inyo National Forest were selected for a pilot baseline monitoring study over five-year intervals to determine potential effects of future climate change on the meadows. Stated as a hypothesis: given the natural range of temporal variability of meadow vegetation, a significant portion of that variability is attributed to the effects of climatic variation. The study is associated with the Global Observation Research Initiative in Alpine Environments Project (GLORIA) hosted by the University of California White Mountain Research Station. Both meadows are sedge–rush–grass wet meadows, or fens, which are sustained by surface water in the form of streams and springs. A comprehensive plant list was compiled and the plant species of each meadow were sampled by a point intercept method along two randomly placed transects. The occurrence of all species at predetermined one-meter interval sample points along the transects were recorded, percent occurrence was calculated, and descriptive statistics were done. The monitoring objective is to detect a 20% biologically meaningful change in the vegetation over time with 90% confidence, and accept a 10% chance of a false change error (Type 1 error). Monitoring is planned to be done in conjunction with tracking change in precipitation and temperature. Three indicators of possible climate change were chosen. One indicator is increase in the abundance of those species whose upper range is at or below meadow elevations. The rationale for this indicator is based the 2007 IPCC report estimation that a doubling of atmospheric CO 2 will increase global temperature with a best estimate of +3.0 °C. Assuming that the present general lapse rate of −6.32 °C per kilometer for the White Mountains will persist, a 3.0 °C increase may result in an equivalent elevation of the meadows of about +475 m. Published elevation ranges indicate that most recorded species are not likely to be affected by the estimated temperature increase. Second and third indicators are a shift in cover from wet meadow to dry meadow species, and the presence and increase of shrub species resulting from postulated reduced precipitation with drying of meadows and encroachment by surrounding shrubs (sagebrush and rabbitbrush). This monitoring study has the potential to detect long-term responses of vegetation to climate change, and reduce uncertainties and confirm or correct the expected consequences of temperature change.