Introduction History and Invasion Patterns of Ammophila arenaria on the North Coast of California

European beachgrass ( Ammophila arenaria [L] Link), introduced to stabilize sand, is fully naturalized in central and northern California and has supplanted populations of native dune plants in many areas, including the North Spit of Humboldt Bay. We interpreted air photos of the North Spit for the presence of Ammophila arenaria at three points in time: 1939/1942, 1962, and 1989. To quantify the spread and to detect invasion patterns of Ammophila , we then compiled maps using a geographic information system. We documented introduction dates and locations to improve the accuracy of our photo interpretation. Interpretation of the three photo series revealed invasion and expansion of Ammophila in both foredunes and inland dunes. The most dramatic increase in cover was found in the foredunes, whereas documented and presumed plantings were found mostly on inland dunes. Adjusting for intentional eradication, Ammophila cover on the North Spit was found to have increased between 1939 and 1989 by 574%. The square root of the area occupied by Ammophila on the North Spit increased linearly with time, conforming to biological invasion theory.     

VALUE OF WOODY RWER CORRIDORS IN LEVEE PROTECTION ALONG THE MISSOURI RWER IN 19931

ABSTRACT: Following the Midwest flood of 1993, a study was initiated along a 39-mile segment of the Missouri River to determine if there was an association between woody corridors and levee stability. A systematic sample of levee failures revealed that primary levees which did not fail had a significantly wider woody corridor than failed levees. Analysis of the total inventory of failed levees revealed that as the width of the woody corridor decreased, the length of the levee failure increased. Number of levee failures and their severity of damage could be reduced if woody corridors were at least 300 feet wide.