Landsat-based monitoring of landscape dynamics in Olympic National Park: 1985-2010

Copass, Catharine; Antonova, Natasha; Clary, Shelby

As part of Vital Signs Monitoring, the North Coast and Cascades Network (NCCN) of the National Park Service (NPS) developed a protocol for monitoring landscape dynamics using Landsat satellite imagery. The protocol was implemented at Olympic Park (OLYM) in 2014 using LandTrendr (Landsat-based Detection of Trends in Disturbance and Recovery) algorithms developed by the Laboratory for Applications of Remote Sensing in Ecology (LARSE) at Oregon State University. We mapped eight categories of landscape change that occurred at OLYM and surrounding areas from 1985 to 2010: Avalanches, Clearing, Development, Fire, Mass Movements, Progressive Defoliation, Riparian, Tree Toppling, and Winter Ice. The Avalanche category captures long, linear change which partially or completely removes vegetation from the valley wall following a release of a large mass of snow down a mountain side. Clearings are areas under forest management where practices vary from thinning to clearcuts. The Development category captures changes associated with complete and persistent removal of vegetation and transformation to a built landscape. Changes due to Fire vary in intensity from full canopy removal to partial burns that leave behind a mixture of dead and singed trees. The Mass Movement category includes both landslides found on valley walls and debris flows associated with steep gradient streams. Progressive Defoliation is a change type in which the forest cover remains but vigor has declined due to insect infestation, disease or drought. Riparian changes are restricted to the valley floors alongside major streams and rivers and capture areas where either conifer or broadleaf vegetation previously existed and has been converted to river channel. Change due to Tree Toppling is evidenced by fallen, broken or topped trees, generally due to wind but sometimes to root rot. Winter ice is a category created to capture forest damage due to a unique combination of large quantities of snow and a windstorm at higher elevations. Only changes larger than 0.8 ha (2 ac) and for which the duration of the period of landscape change was less than 4 years were mapped. The OLYM study area is 1,146,810 hectares, of which 32% (368,593 ha) is within the park boundary. Approximately 159,631 ha (13.9%) of the study area underwent detectable change at some point during the 26 year period of analysis, affecting about 0.98% of OLYM and about 20.1% of the area outside the park boundary. The annual average area impacted by landscape change within the study area was about 6,001 ha. Within the park boundary, the annual average area undergoing change was about 138 ha. Clearing was the major change type within the study area over the last 26 years, followed by Tree Toppling and Development. Inside the park, Fire was the most significant agent of landscape change, with Tree Toppling and Riparian contributing significantly to total change. The inter-annual variability in the total area experiencing landscape change was considerable. The greatest amount of change outside the park boundary was documented in 1988 and was associated with the Clearing category. Inside the park, 2008 was the year with greatest change, due to several winter storms that caused high levels of change in the Tree Toppling, Riparian and Mass Movement categories.

Landsat-based monitoring of landscape dynamics in Olympic National Park: 1985-2010

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