Document: JIQ-3-66-25

Energy flows in peatlands and their responses to heat and water loading.

CHEN, J.* ¹, S.BRIGHAM ², J.PASTOR ³, J.WELTZIN ⁴, X.WANG ¹, C.HARTH ³, B.DEWEY ³, J.KELLER ² and K.UPDEGRAFF ³

Michigan Technological University ¹
University of Notre Dame ²
University ofMinnesota, Duluth ³
University of Tennessee ⁴

Abstract:
This study was designed to examine feedbacks between energy balance and vegetation under different water and heat loading in bogs and fens. Energy flows of net radiation (Rn) and soil heat (G) in 54 mesocosm plots were continuously measured at 30-min intervals since Oct., 1998 using an automated energy budget system to detect underlying mechanisms causing temperature changes. These plots were randomly treated with 3 levels of infrared loading and water-table elevation in a full-factorial design with 3 replications. Our results indicated that there are no significant differences in Rn (P<0.02) within any treatment. Large differences in G were recorded for between fen and bog mesocosms, suggesting vegetation plays a critical role in partitioning Rn. These differences were well reflected in soil vertical temperature gradients (Ts) and were related to physical properties (e.g., thermal conductivity). Large differences in Ts were detected in spring and fall, with little difference in the summer and winter. Ts at 40 cm in heated plots were >0 C in early March, 20 to 40 days before unheated plots reached the same level in April. Bogs appeared to be more sensitive than fens in Rn, G, and Ts. Most importantly, peatlands with infrared heat loading were significantly (>4 C) cooler than those unheated plots throughout the winter, likely because of reduction of snow cover. Our results suggested that global warming can cause soil cooling during the winter. Such unexpected effects will likely happen in the southern-edge of snow in temperate areas.

Keywords: energy balance, ecosystem,warming, wetlands

This abstract is being presented at: 3:30 PM in session:
CLIMATE CHANGE