User:Cassidar/Landscape limnology

Landscape limnology is the spatially explicit study of lakes, streams, and wetlands as they interact with freshwater, terrestrial, and human landscapes to determine the effects of pattern on ecosystem processes across temporal and spatial scales. Limnology is the study of inland water bodies inclusive of rivers, lakes, and wetlands; landscape limnology seeks to integrate all of these ecosystem types.

The terrestrial component represents spatial hierarchies of landscape features that influence which materials, whether solutes or organisms, are transported to aquatic systems; aquatic connections represent how these materials are transported; and human activities reflect features that influence how these materials are transported as well as their quantity and temporal dynamics.

Foundation
The core principles or themes of landscape ecology provide the foundation for landscape limnology. These ideas can be synthesized into a set of four landscape ecology themes that are broadly applicable to any aquatic ecosystem type, and that consider the unique features of such ecosystems.

'''A landscape limnology framework begins with the premise of Thienemann (1925). Wiens (2002): freshwater ecosystems can be considered patches.''' As such, the location of these patches and their placement relative to other elements of the landscape is important to the ecosystems and their processes. Therefore, the four main themes of landscape limnology are:

(1) Patch characteristics: The characteristics of a freshwater ecosystem include its physical morphometry, chemical, and biological features, as well as its boundaries. These boundaries are often more easily defined for aquatic ecosystems than for terrestrial ecosystems (e.g., shoreline, riparian zones, and emergent vegetation zone) and are often a focal-point for important ecosystem processes linking terrestrial and aquatic components.

(2) Patch context: The freshwater ecosystem is embedded in a complex terrestrial mosaic (e.g., soils, geology, and land use/cover) that has been shown to drive many within-ecosystem features and processes such as water chemistry, species richness, and primary and secondary productivity.

(3) Patch connectivity and directionality: The complex freshwater mosaic is connected to the particular patch of interest and defines the degree to which materials and organisms move across the landscape through freshwater connections. For freshwater ecosystems, these connections often display a strong directionality component that must be explicitly considered. For example, a specific wetland can be connected through groundwater to other wetlands or lakes, or through surface water connections directly to lakes and rivers, or both, and the directionality of those connections will strongly impact the movement of nutrients and biota.

(4) Spatial scale and hierarchy: Interactions among terrestrial and freshwater elements occur at multiple spatial scales that must be considered hierarchically. The explicit integration of hierarchy into landscape limnology is important because (a) many freshwater ecosystems are hierarchically organized and controlled by processes that are hierarchically organized,  (b) most freshwater ecosystems are managed at multiple spatial scales, from policy set at the national level, to land management conducted at local scales, and (c) the degree of homogeneity among freshwater ecosystems can change in relation to the scale of observation.

Lake Classification
Landscape limnology principles have been used to classify lakes into groups that can be used to inform management decisions. These principles suggest that there are many smaller ecosystems in an interconnected larger landscape. Because of this, blanket management across the landscape is often ineffective on the smaller scale, and localized management does not necessarily affect the larger landscape. A system was developed to classify lakes by nutrient regulation, water quality, etc., and put those lakes into different categories based on what conservation goals need to be met, which could have a variety of applications for scientists and lake managers.

Nutrient Regulation and Water Quality
Connectivity between lakes, streams, and watersheds plays an important role in nutrient regulation in aquatic systems. Systems that are more connected are able to move nutrients more efficiently between water bodies than areas that are isolated or have long distances between connections. For example, lakes that are more connected with other lakes or streams retain phosphorus for shorter periods of time than lakes that are more independent. Connected systems also see a greater influence of land use on lake nutrients. More connected systems can accumulate nutrients from a greater area through runoff or seepage. This pattern can be seen in more complex spatial patterns as well. Lakes that are considered headwater lakes are influenced far less by drainage and connectivity with regards to nutrients than more lowland water bodies that have a greater chance to accumulate nutrients from the surrounding area. Due to the dynamics of how lakes and water bodies transport nutrients across the landscape, there can be differences in how lakes are able to mediate different variables of water quality. One study found that in some cases, connectivity helps to mediate water quality, while in other cases the idea of patch distinctiveness is more important in determining water quality. Landscape limnology has also been used by the US National Surface Water Survey to determine the effects of acid depositions on lakes and their connective streams.

Connection to Agriculture
Landscape limnology helps to connect lake systems with the terrestrial systems surrounding them. Studying how terrestrial and lake characteristics plays into shoreline characteristics is a growing area of interest, and the proximity of agriculture is especially important in this. Along with other variables, the ratio of catchment area to surface area of the lake and the percentage of agriculture in the catchment area compared to forest cover can help predict the likelihood of eutrophication in a lake. The location of this agriculture in relation to the water bodies is important as well. If the amount of agriculture closer to near-stream areas is high, there is a higher chance that nutrients within the aquatic system will also be high. Thus the spatial location of factors within a landscape is just as important as the heterogeneity of the landscape.

Biota
Landscape limnology principles have been used in many studies of biological communities. Scientists have used these techniques to analyze fish populations over a region, and one study found that the fish migrate between lakes, so connectivity is very important in aquatic systems, where previously the lakes had been seen as more discrete features. In another study in the Amazon river region, scientists found that landscape effects differ based on season. In the dry season, lakes become isolated from the rest of the system, which influences fish-phytoplankton interaction. However, in the wet season, lakes become highly connected to each other and the rest of the system, and then the only predictor of phytoplankton biomass is lake depth, rather than fish controlling biomass in the dry season.