Department

Botany

First Advisor

Dr. Dave Williams

Description

The Altiplano in Bolivia lacks instrumental weather records with sufficient spatial and temporal resolution to understand changes in the pattern and intensity of El Niño Southern Oscillation (ENSO). We evaluated the potential for the long-lived columnar cactus Echinopsis atacamensis to record changes in precipitation and climate. For this study a single, central spine was collected and then analyzed for its δ18O and δ13C isotopic ratios. In addition, five spines were collected from different heights and analyzed for their radiocarbon (14C) content to calibrate growth rate and determine the age of the cactus. The δ18O values ranged from 30‰ to 59‰ reflecting substantial intra- and inter-annual variation of precipitation (lower δ18O values) and transpiration (higher δ18O values). The δ13C values ranged from -7‰ to -11‰, illustrating strict night only CO2 uptake, opposed to carbon fixation during both the day and night. The majority of the spine series showed similar trends between δ18O and δ13C both in magnitude and direction. These data suggest that both isotopes are directly related to cactus physiology and do not vary independently. To further understand the link between water availability and cactus physiology; data with known lake water levels were incorporated. These data suggest that cactus spines provide an indirect record of climate and may be an appropriate tool for historic climate reconstruction.

Comments

Oral Presentation, Wyoming NSF EPSCoR and UW Honors Program

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Reconstructing the Past: Using stable isotopes from cactus spines to reconstruct past climate in South America

The Altiplano in Bolivia lacks instrumental weather records with sufficient spatial and temporal resolution to understand changes in the pattern and intensity of El Niño Southern Oscillation (ENSO). We evaluated the potential for the long-lived columnar cactus Echinopsis atacamensis to record changes in precipitation and climate. For this study a single, central spine was collected and then analyzed for its δ18O and δ13C isotopic ratios. In addition, five spines were collected from different heights and analyzed for their radiocarbon (14C) content to calibrate growth rate and determine the age of the cactus. The δ18O values ranged from 30‰ to 59‰ reflecting substantial intra- and inter-annual variation of precipitation (lower δ18O values) and transpiration (higher δ18O values). The δ13C values ranged from -7‰ to -11‰, illustrating strict night only CO2 uptake, opposed to carbon fixation during both the day and night. The majority of the spine series showed similar trends between δ18O and δ13C both in magnitude and direction. These data suggest that both isotopes are directly related to cactus physiology and do not vary independently. To further understand the link between water availability and cactus physiology; data with known lake water levels were incorporated. These data suggest that cactus spines provide an indirect record of climate and may be an appropriate tool for historic climate reconstruction.