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
When does arrangement matter to ecosystem function: Interactions between the amount and configuration of land cover types.
Gergel, Sarah1, 1
ABSTRACT- Understanding the effect of landscape configuration on the functioning of ecosystems is an emerging challenge in ecology. Case studies in agricultural landscapes with riparian buffer zones have shown that buffers can reduce nutrient and sediment loading to aquatic systems. However, the relative abundance of 'source' and 'sink' cover types in the rest of a watershed might also affect total loading to downstream surface waters. I used a series of increasingly complex landscape models to determine if there are interactive effects between the abundance of source/sink cover types and the arrangement of such cover types in influencing total loading to surface waters. I used both a simplified, heuristic source/sink model as well as a realistic, distributed hydrologic watershed model of storm events. Replicated simulation experiments were conducted using a factorial design to test for effects of the amount of land in source/sink versus the effect of different spatial arrangements of those cover types. I simulated loading in watersheds with 10, 30, 60 and 90 percent of the watershed occupied by 'source' areas, crossed with clumped, fragmented, random and buffer strip arrangements. I also examined the effect of varying the relative strengths of source/sink habitats. In a random landscape, the variance in loading increases for intermediate abundances of source/sink, suggesting that the particular arrangement of land is more critical to determining total loading in landscapes with this ratio of source/sink cover types.
KEY WORDS: landscape models, nutrient loading