Thesis

Physiological Effects of Sulphur Dioxide Induced Stress on Vegetation Under Natural Conditions

ABSTRACT PHYSIOLOGICAL EFFECTS OF SULPHUR DIOXIDE INDUCED STRESS ON VEGETATION UNDER NATURAL CONDITIONS by Michael W. Jenkins Master of Science in Biological Sciences California State University, Chico Spring 2011 This research incorporated a series of experiments using leaf level gas exchange, chlorophyll fluorescence and remotely sensed reflectance measurements of vegetation with long-term chronic exposure to volcanic gas emissions under natural conditions. The experiments were conducted on poor man’s umbrella, or sombrilla de pobre (Gunnera insignis), along an elevation gradient of 1939 to 3280 meters on an access road to Parque Nacional Volcán Turrialba in Costa Rica, with corresponding sulphur dioxide (SO2) and carbon dioxide (CO2) measurements. Results obtained identified chlorophyll fluorescence parameters of quantum yield (Fm’-Fs/Fm’) and electron transport rate (ETR) were strongly correlated with SO2 concentration (r2=0.801 and 0.799), respectively. The most useful reflective index developed and incorporated in this study was that based on the double-peak feature or the double peak optical index (Dpi), (D702xD715)/D7082). Strong correlations were identified between Dpi and SO2, Fm’-Fs/Fm’, ETR and CO2 with (r2 = 0.975, 0.945, 0.942 and 0.801), respectively. Moreover, Dpi was at least moderately correlated with every physiological measurement in this study. This study site is a natural environment with high hydrothermal activity that results in significant SO2 emission. Along with the increased SO2 a substantial increase in CO2 concentration was identified. To emphasize the physiological interaction SO2 and CO2 concentrations have on vegetation a ratio of SO2/CO2 concentrations was developed. The SO2/CO2 ratio and Dpi index were strongly correlated (r2 = 0.927).

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