This is part of an ongoing monitoring project that the Biogeographic Data Branch of the California Department of Fish and Game (DFG), in collaboration with the Department of Water Resources and the DFG Water Branch, started in 1999 to track changes in the Suisun Marsh vegetation over time. This is the third update since the original map was made in 1999. Orthorectified, true color imagery was flown in June 2006 to mimic as close as possible the June 1999 and June 2003 Suisun imagery time frame and plant phenology. This imagery was received as 427 high quality, individual, flight line ortho-photographs. The aerial imagery was interpreted and changes were made to the vegetation polygon shapefile using ArcMap 9.2 (ESRI?). The criteria for a polygon to be considered "changed" were first laid out in the change detection report for 2003 (Vaghti and Keeler-Wolf 2004), and are repeated here: The following changes were considered significant and consistently interpretable, and were assessed: " A greater than 20% change in acreage of an exiting small polygon (<1 acre) " A greater than 10% change in acreage of a mid-sized polygon (1-5 acres) " A greater than 5% change in a large polygon (>5 acres) " A type conversion of a vegetation polygon dominated by perennial species. Type conversion, as defined here, occurs when a previously mapped vegetation type dominated by perennial species has changed based on the decision rules set forth in the vegetation mapping unit key defined in Table 5 of Vegetation Mapping of Suisun Marsh, Solano County (Keeler-Wolf et al. 2000), or when an annual species dominated vegetation type is converted to a perennial vegetation type. " A persistent physical change has altered any vegetation polygon and partially or entirely replaced it with a non-vegetated area (non-vegetated areas include buildings, dredged ditches, new levees, roads, or other human engineered structures). " A change in management style, which includes a conversion or restoration from an actively managed situation (annual burning, disking, plowing, flooding, or other management practice which annually disturbs the vegetation) to a passively managed, or un-managed, situation. The following changes were considered non-significant and/or unreliably interpretable and were not assessed: " Annual to annual type conversion were not considered because of the vagaries of climate on annual vegetation. Appendix 2 highlights these excluded types in yellow. " Polygons that are regularly heavily managed by annual burning, disking, flooding, or other means were not considered. These changes, unless they show some direction (e.g., from passive management to active, or vice versa), are considered regular management perturbations and maintain the same general vegetation pattern through regular disturbance. A copy of the 2003 vegetation polygon shapefile was made and modified for the 2003-2006 change detection and then it was linked to a new 2006 Microsoft Access® table for data entry. For consistency the attributes and vegetation types for the 2006 change detection remained the same as in 2003. When changes in size or shape of polygons were detected, they were cut using the "Cut Polygon Features" task and then merged using the "Merge" option in ArcMap.