Soil Moisture Index
In the case of the MAV, sites that have been ditched to hasten drainage (loss of hydrologic indicators) and intensively cropped (loss of vegetative indicators) are commonplace, thereby leaving soils as potentially the only reliable wetland indicator. These facts underlie the need for quality data representing the spatial distribution of soil moisture characteristics. The Soil Moisture Index, a project jointly funded by the USDA Forest Service and DU, was created for use as a surrogate for digital hydric soils data for the MAV using Landsat satellite imagery acquired during the drought conditions of winter 1999. Using winter drought imagery ensured a more accurate evaluation of soil moisture-retention capacity by minimizing the effects of vegetation in agricultural fields and surface water in satellite imagery analysis. SMI values were only determined for bare soil sites; all sites with ground cover during the winter of 1999 were not assigned a class value.
The clearing of the MAV's forests generally occurred from the highest and driest sites to lowest and wettest. By identifying the most recently cleared areas and establishing a chronology of deforestation, analysts can identify those sites that were or are the wettest and only recently became viable to convert to agriculture because of flood control and the rise of new crop alternatives, namely soybeans. However, the fall of certain agricultural commodity prices and the rise of reforestation incentive programs for landowners over the past two decades have spurred a reversal of the trend in such a way that it is now precisely these areas of recent forest change that are prime candidates for reforestation and wetland restoration. Because the extents of bottomland hardwood forests are fairly conspicuous in aerial surveys, they represent the single most assessable indicator of wetland vegetation for MAV-wide analyses. In order to achieve the goal of quantifying and modeling forest loss in the MAV, DU and the USDA Forest Service jointly funded two projects, with the collaboration of numerous partners in the Lower Mississippi Valley Joint Venture partnership, that quantifies the forest extents and rates and locales of forest change for the late 1940s using historic aerial photos on through the 1970s, 1980s, 1990s and 2001 using Landsat satellite imagery.
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