Monitoring Riparian landscape change and modeling habitat dynamics of the yellow-billed cuckoo on the Sacramento River, California

The habitat dynamics of the meandering sector of the Sacramento River riparian landscape are driven by three primary agents of change: (1) the physical processes of natural river channel migration and floodplain dynamics, (2) the high growth rates of riparian woody vegetation species, and (3) the cultural land use practices of agricultural land development. Three studies were conducted to examine these agents of change and their conservation implications. To establish a baseline, the first study compared the historical spatial distribution of the Sacramento River riparian zone (ca. 1800) to more current conditions (ca. 1970s) and found 5.5% to remain in the reach between Red Bluff and Sacramento.; The second study examined the riparian landscape dynamics of a study reach from river miles 196–219 mapped over six time periods from 1938–1997. Each mapped time period was entered into a geographic information system (GIS) for analysis. Trends are reported for each habitat type and floodplain dynamics were analyzed from 1896–1997 to derive a floodplain age map. Results from a spatial analysis of the proportions of riparian forest patch height classes within each of the floodplain age classes indicates that low and medium-height vegetation classes (<20 meters) dominate within the younger floodplain age classes (<20 years) and high vegetation classes (>20 meters) dominate within the older floodplain age classes (>20 years). The descriptive state-and-transition analyses findings indicate the low and medium height patches have the highest frequency of change. The results imply channel hydrodynamics and meander migration play a significant ecological role in maintaining the heterogeneity of forest structure in riparian landscape mosaics on the Sacramento River.; The third study assessed riparian landscape function by developing and testing a GIS habitat suitability index (HSI) model for the yellow-billed cuckoo, an endangered species in California. The HSI model was applied to the historical GIS data sets to demonstrate the temporal variation in the location of suitable core habitats. Findings suggest that essential habitat patches are a shifting mosaic: habitat has shifted up to 6 kilometers in location in as few as 12 years and habitat can develop in as little as 9 years and is functional for up to 30 years.