Spatial pattern and dynamics of hardwood patches in the Coast Range of Oregon, 1939-1993

Graduation date: 2000Analysis of the long-term spatial pattern and dynamics of hardwood patches in\ud the Coast Range of Oregon provides numerous ecological insights. Natural and\ud anthropogenic disturbances have contributed to the development of a patchy mosaic of\ud vegetation types in the area. Some hardwood patches in the Coast Range may be the\ud precursors to stable vegetation states. The five objectives for the study were to: 1)\ud develop the methodology for studying patch dynamics at landscape scales; 2) describe\ud changes in the areal extent and occurrence of hardwood patches; 3) characterize the\ud sizes and shapes, and size and shape changes of hardwood patches in the west-central\ud Coast Range of Oregon; 4) describe the shift in within-patch heterogeneity and within-patch\ud vegetation composition features of hardwood patches; and 5) characterize patches\ud occurring in riparian areas. A viable methodology was developed for the detailed study\ud of the change in vegetation patches across landscapes using scanned, georeferenced\ud aerial photos, aerial photo interpretation of hardwood patches, and GIS techniques.\ud Patch locations and characteristics were compared to a suite of environmental and other\ud variables. The hardwood patch mosaic was not a stable landscape feature. The total\ud area covered by hardwood patches, the weighted mean size of hardwood patches, and\ud the number of patches sampled declined from 1939 to 1993. Forest Service lands\ud showed the most dramatic drop in hardwood area, while private non-industrial lands\ud showed the most dramatic increase in hardwood area. Most patches present in 1939\ud either disappeared or decreased in size. In 1993, hardwood patches were found closer to\ud streams and on lower slope positions than in 1939. This may be associated with historic\ud disturbance patterns of fire, logging, and grazing that occurred on the upper slopes,\ud allowing for alder establishment on these sites. Hardwood patch shapes became more\ud complex over time, especially in riparian areas. Core area:edge area ratios increased.\ud Hardwood patches were less heterogeneous in within-patch composition than expected,\ud with large conifers the main non-hardwood cover type within patches; within-patch\ud heterogeneity declined during the study period. Recent management practices are likely\ud increasing hardwood fragmentation and shape complexity, and restricting the landscape\ud distribution of hardwood patches