Jeffrey T. Maxted

Landscape Planning for Agricultural Nonpoint Source Pollution Reduction I: A Geographical Allocation Framework

Agricultural nonpoint source pollution remains a persistent environmental problem, despite the large amount of money that has been spent on its abatement. At local scales, agricultural best management practices (BMPs) have been shown to be effective at reducing nutrient and sediment inputs to surface waters. However, these effects have rarely been found to act in concert to produce measurable, broad-scale improvements in water quality. We investigated potential causes for this failure through an effort to develop recommendations for the use of riparian buffers in addressing nonpoint source pollution in Wisconsin. We used frequency distributions of phosphorus pollution at two spatial scales (watershed and field), along with typical stream phosphorus (P) concentration variability, to simulate benefit/cost curves for four approaches to geographically allocating conservation effort. The approaches differ in two ways: (1) whether effort is aggregated within certain watersheds or distributed without regard to watershed boundaries (dispersed), and (2) whether effort is targeted toward the most highly P-polluting fields or is distributed randomly with regard to field-scale P pollution levels. In realistic implementation scenarios, the aggregated and targeted approach most efficiently improves water quality. For example, with effort on only 10% of a model landscape, 26% of the total P load is retained and 25% of watersheds significantly improve. Our results indicate that agricultural conservation can be more efficient if it accounts for the uneven spatial distribution of potential pollution sources and the cumulative aspects of environmental benefits.

A spatial autocorrelative model for targeting stream restoration to benefit sensitive nongame fishes

Stream restoration projects often aim to benefit aquatic biota and frequently use the reappearance of sensitive nongame fish species as a measure of restoration success. However, mitigation of human influence will only benefit a given species where static habitat characteristics are suitable for that species and where potential source populations are within the range of their dispersal capability. We used spatial autoregressive habitat models to simulate the effect of watershed-scale stream restoration on the distributions of six sediment-sensitive fish species in Wisconsin, USA, streams. These models consider the probability of occurrence of a species in a given stream segment as a function of characteristics of that segment as well as the characteristics of neighboring segments. Populations of individual species are predicted to be restorable in 0.2%–2.8% of Wisconsin streams. Streams with high restoration potential for one or more species generally have high watershed human land use but are also closel...

Assessing the influence of upstream drainage lakes on fluvial organic carbon in a wetland‐rich region

[1] The role of aquatic ecosystems in regional and global carbon cycles is becoming increasingly apparent, and lakes and reservoirs may be particularly important to the retention and processing of organic carbon. If this is the case, then lakes and reservoirs may act as control points that decrease OC concentrations and fluxes in downstream aquatic ecosystems. We tested this hypothesis at a regional scale by comparing dissolved organic carbon (DOC) concentrations and fluxes in 52 randomly selected streams and rivers with and without upstream lakes in the water-rich Northern Highlands Lake District (NHLD), Wisconsin, USA. DOC concentrations were significantly higher (p 0.49). Likewise, there were no significant differences in DOC:DON or DOC:DOP ratios, or in yields from watersheds with and without upstream lakes after compensating for wetland influences. We suggest that lake OC storage or processing may be limited by high hydrologic flushing in lakes with stream outlets and overwhelmed by larger scale influences of landscape composition in the NHLD. Consequently, drainage lakes in carbon-rich regions like the NHLD may have limited influence on terrigenous carbon exports to the ocean.