DONALD SIEGEL AS A PIONEER IN PEATLAND HYDROLOGY

Don Siegel has been an important pioneer in the expanding field of hydrogeology for more than three decades. Don's forte remains his uncanny aptitude for working within large interdisciplinary groups that seek his intuitive grasp of both chemical and physical hydrogeology. His ability to attract talented students and inspire them to work together as part of a research team has also been the hallmark of Don's long academic career. These skills enabled Don to make seminal contributions to many fields of study including peatland hydrology. Beginning in the early 1980s Don and his colleagues first challenged the prevailing concept that the deeper portions of peat deposits were essentially closed systems with respect to fluid and solute fluxes as well as the production of greenhouse gases. Not only did he show that the hydraulic conductivity of the deep peat was much higher than previously reported but he also presented solute and hydraulic head profiles that confirmed the upward transport of groundwater through the profiles of two peat mounds in northwestern Minnesota.

A decade later Don and his colleagues discovered that large pools of methane were stored within the deepest portions of peat deposits across northwestern Minnesota. This discovery defied the established dogma that methane production was largely limited to the near-surface layers of a peat deposit where labile carbon substrates are most abundant. However, the deep recharge systems that prevailed during this period apparently transported labile carbon substrates downward into the deepest pore waters in quantities sufficient to fuel the production of biogenic gas bubbles. The exceptionally tight linkage among climate, hydrology, and methane production in these peatlands has subsequently been confirmed by ongoing research. These studies also demonstrate the capacity for biogenic gas bubbles to deform the peat fabric and alter its interconnected pore system. This research program demonstrates an ever closer coupling of hydrologic and biotic processes in boreal peatlands inviting mathematical modeling to understand their linkages to climatic change.