PARENT SESSION
Symposium #19: Integrating aquatic and terrestrial biogeochemistry in heterogeneous landscapes.
Sponsored by ESA Aquatic Ecology Section
Organized by: N.B. Grimm, S. E. Gergel, and W. McDowell.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Lecture Hall
Hot spots and hot moments in landscape biogeochemistry.
McClain, M1, Dent, L2, Gergel, S3, Grimm, N4, Harvey, J5, Mayorga, E6, McDowell, W7, Pinay, G8, 1 2 3 4 5 6 7 8
ABSTRACT- Zones of enhanced biogeochemical processing are frequently referred to as hot spots. For example, hot spots of denitrification are associated at small scales with anoxic microsites in a soil matrix and at large scales with riparian and hyporheic zones in a watershed. The concept of hot spots may also be extended to time. "Hot moments" are thus periods of time during which rates of biogeochemical processes are enhanced. Examples include periods of snowmelt in alpine watersheds that cause rapid leaching of organic carbon and rainstorms in cold desert plant communities that stimulate nitrogen uptake. Hot spots and hot moments have the following characteristics: (1) Hot spots occur where hydrological flow paths carrying complementary reactants intersect, or where hydrological flow paths encounter substrates containing missing reactants, (2) Hot moments occur when episodic hydrological flow paths reactivate and mobilize accumulated reactants or when other forcing variables deliver reactants to hydrologic flow paths. Hot spots and moments may occur separately, but often they interact such that high reaction rates occur over short periods of time in specific locations. The concept of hot spots and moments can be extended across nearly all spatial (molecular to global) and temporal (millisecond to eon) scales. Greater consideration of biogeochemical hot spots and hot moments is needed to improve our understanding of biogeochemical functioning in both terrestrial and aquatic ecosystems and for making more effective resource management decisions.
KEY WORDS: biogeochemistry, nitrogen, carbon, land-water interactions