Study System: Sonoran Desert Streams and Wetlands
Dr. Heffernan's dissertation research addressed the causes and consequences of wetland establishment in Sonoran Desert streams. Cienegas (Spanish for 'marsh') were once a widespread feature of drainages in the Southwestern US, but these wetlands underwent region-wide erosion and downcutting in the second half of the 19th century. Long-term study of southwestern streams has largely neglected this ecosystem type because of its present rarity. Dr. Heffernan's research focused on Sycamore Creek, where the combination of a long flood-free period and elimination of grazing allowed re-establishment of cienegas in sections where groundwater sustained the surface stream during this period. Once established, these wetlands were able to withstand large floods that would eliminate less-dense vegetation. The establishment of wetlands also led to dramatic changes in hydrologic and biogeochemical conditions within these reaches. The identification of cienegas as an alternative stable state has both theoretical relevance (as the first empirical demonstration of multiple states in a stream) and practical importance for their restoration (since alternative state transitions can be very difficult to reverse).
The lab does not have active research in Sonoran Desert streams at present, but some of our colleagues do. We are also still working on conceptual papers that use Sonoran Desert streams as model systems. If you think you might be interested in cienegas as study systems, there is still lots to do! We are working on conceptually-related problems in the Everglades, and maybe soon in coastal wetlands of NC.
Further Reading:
Heffernan, J.B., R.A. Sponseller, and S.G. Fisher. 2008. Consequences of a biogeomorphic regime shift for the hyporheic zone of a Sonoran Desert stream. Freshwater Biology 53(9):1954-1968.
Heffernan, J.B. 2008. Wetlands as an alternative stable state in desert streams. Ecology 89(5):1261-1271.
Heffernan, J. B., A. Albertin, M. Fork*, B. Katz, and M.J. Cohen. 2012. Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer. Biogeosciences 9, 1671-1690. doi:10.5194/bg-9-1671-2012
Fisher, S.G., R.A. Sponseller, and J.B. Heffernan(2004). Horizons in stream biogeochemistry: Flowpaths to progress. Ecology 85(9): 2369-2379.
Fisher, S.G., J.B. Heffernan, R.A. Sponseller, and J.R. Welter (2007). Functional Ecomorphology: Feedbacks between Form and Function in Fluvial Landscape Ecosystems. Geomorphology 89: 84-96.
The lab does not have active research in Sonoran Desert streams at present, but some of our colleagues do. We are also still working on conceptual papers that use Sonoran Desert streams as model systems. If you think you might be interested in cienegas as study systems, there is still lots to do! We are working on conceptually-related problems in the Everglades, and maybe soon in coastal wetlands of NC.
Further Reading:
Heffernan, J.B., R.A. Sponseller, and S.G. Fisher. 2008. Consequences of a biogeomorphic regime shift for the hyporheic zone of a Sonoran Desert stream. Freshwater Biology 53(9):1954-1968.
Heffernan, J.B. 2008. Wetlands as an alternative stable state in desert streams. Ecology 89(5):1261-1271.
Heffernan, J. B., A. Albertin, M. Fork*, B. Katz, and M.J. Cohen. 2012. Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer. Biogeosciences 9, 1671-1690. doi:10.5194/bg-9-1671-2012
Fisher, S.G., R.A. Sponseller, and J.B. Heffernan(2004). Horizons in stream biogeochemistry: Flowpaths to progress. Ecology 85(9): 2369-2379.
Fisher, S.G., J.B. Heffernan, R.A. Sponseller, and J.R. Welter (2007). Functional Ecomorphology: Feedbacks between Form and Function in Fluvial Landscape Ecosystems. Geomorphology 89: 84-96.
