The giant reed invasion is of immediate concern in the Russian River watershed. Based on information from river systems in southern California and other riparian areas throughout the world, it is clear that giant reed may be one of the most serious impacts to the remaining riparian habitat in the Russian River system, having a direct impact on the salmonid fishery. Given the fact that the Russian River watershed is home to federally listed salmonid species - steelhead trout, coho and chinook salmon - as well as the federally listed freshwater shrimp and red legged frog, it is imperative that riparian zone management in these ecosystems take into account the impacts of invasive plants. Preservation of the remaining riparian habitat, as well as restoration of fisheries resources, will be more successful, and far more cost effective, if the giant reed issue is addressed during the early phase of this invasion.
USGS Digital Orthogonal Quarter Quadrangles (DOQQ) were used as base maps for the project, for the raster-format underlay for display of the final mapped stands of Arundo, as well as for the calibration of the unrectified low-level Aggregate Resources Management (ARM) Plan aerial photos. Sonoma and Mendocino County USGS DOQQ were developed from 1993 National Aerial Photography Program imagery (1:40,000 photo scale). The project 3.75-minute DOQQ are in the Universal Transverse Mercator coordinate system on the North American Datum of 1983 and have a ground pixel distance of 1 meter.
The Aggregate Resources Management (ARM) Plan aerial photos provided the most detailed, recent and consistent imagery coverage of the mainstem Russian River for photo-interpretation and digitizing individual stands of Arundo . Though these aerial photos were not orthogonally rectified, the terrain within the floodplain study area is relatively level and the mapping results are considered acceptable for purposes of natural resources planning. The set of ARM Plan aerial photographs used in this study were taken by Delta Geomatics, Inc., May 1999, at a scale of 1:4,800. Mylar enlargements of the original photographs, were produced by Delta Geomatics, Inc. for the Middle Reach, Alexander Reach and much of the Fitch Mountain Reach, at a scale of 1:2,400; and reproduced using blueprinting processes. These blue-line prints were used to delineate Arundo feature boundaries, augmented by low level aerial photographs taken by CRP. Arundo polygons not clearly seen in the photographs were identified on the map for future field editing.
In the fall/winter months of 1998, low-level fixed wing aircraft test flights were conducted to determine the best film type, weather conditions, season, photo angle, and plane flight altitude for photographing Arundo in a riparian setting. Both banks of the 115 mile long Russian River mainstem were photographed during several low level flights conducted during the winter months (Jan./Feb. 1999), when riparian plant species were dormant, providing the clearest view of Arundo stands. Attempts were taken to photograph during overcast weather to avoid shadow effect. A series of sequential, overlapping photographs was taken for both banks, at an approximate altitude of 500 feet, at a 45 degree angle, using Kodak Gold color film.
The above photographs were used to enhance monoscopic photo interpretation of the ARM Plan low-level aerial photo coverage (May 1999) of the Alexander Valley, Fitch Mountain and Middle reaches of the Russian River in Sonoma County. The ARM Plan aerial photo coverage was registered to the digital 1:12,000 USGS DOQQ base maps with a minimum of five control points for each blue-line aerial photo enlargement using the projective transformation routine in AutoCAD Release 12.0. Manual digitizing of Arundo donax feature boundaries was performed on a 24" x 36" CalComp Drawing Board II digitizing tablet.
The accuracy of registration between each blue-line enlargement and the base map was measured by the Root Mean Square Error (RMSE), or an accuracy average of all tested points on a map (in statistical terms) and calculated in map units (meters). The USGS National Map Accuracy Standards constrain the maximum acceptable RMSE according to the intended scale of the output maps. Since the output maps for the project were to be plotted at a minimum scale of 1:6,000 (1”=500’), the tolerance value specified by the National Map Accuracy Standards for maps of this scale was used as a guide during the registration operation.
The appropriate RMSE value when registering the blue-line ARM Plan maps to the digital base maps is 3.29180 m (or 0.018 inch in digitizer units). 89% of the individual blue-line sheets for the Arundo coverage were able to meet this standard. 100% of the individual blue-line sheets for the Arundo coverage were able to meet this standard for the output scale 1:12,000 (1”=1000’).
Arundo feature boundaries and location were digitized directly onto the USGS DOQQ base maps using ESRI ArcView 3.1 software, for those areas not covered by the ARM Plan aerial photos, (the Mendocino County Reach, Lower Reach and part of the Fitch Mountain Reach in Sonoma County). The data set for these areas is considered to be less accurate.
Though the extent of Arundo growth and general locations of feature polygons were the main focus of this mapping project, the determination of stand growth-patterns in relation to surrounding vegetation was considered important due to the implications for eradication efforts and long term monitoring. Arundo stands were classified into the following categories:
1. Overstory: discreet stands of Arundo growing as a mono-culture, visible on both the blue-line enlargements and the low-level oblique photograghs.
2. Overstory/Intermixed: stands of Arundo growing as overstory, but intermixed with other same-sized shrubs and trees.
3. Understory: stands of Arundo growing as the understory layer, with an overstory canopy consisting of larger-sized trees.
ArcView 3.1 software was used to convert AutoCAD drawings into a Geographic Information System (GIS) format, allowing data analysis and acreage compilation.
AD2 - Overstory/Intermixed: stands of Arundo growing as overstory, but intermixed with other same-sized shrubs and trees.
AD_under - Understory: stands of Arundo growing as the
understory layer, with an overstory canopy consisting of larger-sized
trees.
Attribute_Label: LAYER