Agriculture and urban development are prominent features in the landscape and natural land cover will continue to be converted to accommodate expanding populations and economic growth. These land use disturbances have implications for ecosystem integrity and functioning, and aquatic ecosystems may be especially vulnerable to disturbances because of their strong hydrological connectivity to the surrounding landscape. My research interests lie in applying the principles of landscape ecology to study ecosystem integrity and functions in freshwater environments impacted by anthropogenic disturbances such as land use change and global climate change. These interests fit in the emerging field of landscape limnology. I find this landscape limnology approach attractive because it uses digital geographic information technology, which is becoming widely available, to address broad scale ecological processes that are likely overlooked in more traditional aquatic studies. I believe that understanding these relationships will become important in understanding the consequences of a changing landscape and can inform management and conservation of aquatic resources.
Multi-scale landscape and wetland drivers of lake total phosphorus and water color
It is recognized that features in the landscape affect lake water chemistry. Most studies relate lake water chemistry to landscape variables quantified at the catchment scale and ignore landscape features that fall outside these boundaries. However, it has been suggested that lake catchment boundaries may not capture important processes such as groundwater flow and regional agricultural activities that likely affect lake water chemistry. In addition, cross-scale interactions, defined as ecological processes operating at one spatial scale interacting with processes at another spatial scale, can lead to unexpected relationships of catchment variables in different regional settings. Wetlands are likely candidates for cross-scale interactions because wetland effects on lake water chemistry are not consistent from region to region, and wetlands are found in diverse hydrologic and land use settings.
For my M.S. thesis, I quantified relationships between wetland extent in a lake’s catchment and lake total phosphorus (TP) and water color using multilevel mixed-effects models that incorporate landscape features such as hydrogeomorphology and land use at local catchment and regional scales. My three research questions were: 1) Within regions, are wetland relationships with TP and color affected by interactions with local land use or hydrogeomorphic variables, 2) Across, regions are wetland relationships with TP and color different? And if so, 3) Are differences in wetland relationships with TP and color related to cross-scale interactions? We found that wetland-TP and wetland-color relationships were not affected by local-scale interactions. For the second question, we found that wetland-TP and wetland-color relationships were different across regions, and these differences were related to cross-scale interactions with regional landscape characteristics. Regional human land-use interacted with wetland-TP relationships such that in regions with high amounts of agriculture, wetlands were associated with decreased lake TP; but in regions with low amounts of agriculture, wetlands were associated with increased lake TP. In contrast, regional hydrogeomorphic characteristics interacted with wetland-color relationships such that in regions with high groundwater contribution, the strength of wetland relationships was weak. The results demonstrate that the regional landscape setting influences wetland relationships with TP and color through cross-scale interactions; and lake TP and color are controlled by both regional- and local-scale landscape variables.
Fergus CE, Soranno PA, Cheruvelil KS, Bremigan MT. 2011. Multi-scale landscape and wetland drivers of lake total phosphorus and water color. Limnology and Oceanography 56(6): 2127-2146. doi:10.4319/lo.2011.56.6.2127. PDF
Data deposited online at Dryad:
Fergus CE, Soranno PA, Cheruvelil KS, Bremigan MT (2011) Data from: Multi- scale landscape and wetland drivers of lake total phosphorus and water color. Dryad Digital Repository. doi:10.5061/dryad.4v2m5
Cross-scale interactions in lake systems
I am part of the MSU’s Landscape Limnology Research Group. Broadly, my research interests lie in identifying spatial and temporal cross-scale interactions that affect lake water chemistry across diverse geographic settings. In particular I am interested in the effects of wetlands on lake water chemistry and how these relationships may change across space and through time. To address these research interests, we are compiling existing lake water chemistry, landscape, and climate data from seventeen states located in the Midwest and Northeast, U.S. I will be building hierarchical Bayesian-spatial models to determine landscape relationships with lake water chemistry and to quantify the degree of uncertainty in parameter estimates. My dissertation research will identify landscape characteristics that may promote cross-scale interactions leading to unexpected lake responses. This information is relevant to continental and global limnology, a research field that addresses broad-scale impacts on freshwater systems.
To explore the role that wetlands play in cross-scale interactions, it is necessary to determine how best to quantify wetlands in the landscape. I will develop a variety of wetland landscape-metrics to test in relation to lake water chemistry – specifically lake total phosphorus (TP), total nitrogen (TN), and water color. Past studies have measured wetlands as the proportion of wetland cover in the catchment or as fixed buffer widths surrounding lake bodies. I am interested in developing metrics that capture wetland connectivity to the freshwater landscape (i.e. the hydrologic connections to lakes, streams, and groundwater). I expect that wetland connectivity is important to nutrient and carbon transport to lakes and affects lake water chemistry.
Multivariate lake TP, TN, and color spatial models
Studies have shown that lake nutrients and carbon measures are correlated to one another and may be controlled by the same lake and landscape characteristics. However, these relationships are variable across regions, and few studies have quantified the relationships between TP, TN, and color across broad geographic extents. Multivariate-spatial models for TP, TN, and color explicitly quantify the interrelationships among lake response variables, and thus are more informative than individual lake response models. These multivariate relationships can identify where water chemistry correlations are strong and where correlations are weak. In addition, multivariate relationships can be used to predict lake chemistry where measurements are missing by borrowing strength from other lake chemistry variables. For example, we may be able to predict water color from a multivariate TP, TN, and color model in locations where TP and TN were measured but water color was not. Finally, multivariate relationships will improve our understanding of nutrient and carbon dynamics and could identify new nutrient and carbon landscape sources and in-lake processing.
In my free time I enjoy spending time outdoors doing activities such as jogging, kayaking or cross country skiing depending on the time of the year. Over the past two years I have made the annual pilgrimage to Point Pelee, Ontario to welcome the incoming migratory song birds. Although my bird identification skills are rather poor I hope to be more actively involved in the local Audubon Society.