GNN Mapping of Existing Vegetation, Pacific Coast States

Major funders and collaborators

Project summary

This project involved developing detailed maps of existing forest vegetation and land cover across all land ownerships in the Pacific Coast States (Oregon, Washington, and parts of California). The mapping was integrated with ongoing sample-based forest inventories conducted by the Forest Inventory and Analysis program (FIA) at the PNW Station, and Current Vegetation Survey of Region 6, USDA Forest Service, and the BLM in western Oregon. For each of our modeling regions, we used gradient imputation (Gradient Nearest Neighbor, or GNN; Ohmann and Gregory 2002) to map detailed vegetation composition and structure for areas of forest and woodland. GNN uses multivariate gradient modeling to integrate data from FIA field plots with satellite imagery and mapped environmental data. A suite of fine-scale plot variables is imputed to each pixel in a digital map, and regional maps can be constructed for many of the same vegetation attributes available for FIA plots. Nonforest areas were mapped using Ecological Systems developed in a related LEMMA project. All GNN map products are grid-based at 30-m spatial resolution.

The mapping work was organized geographically around modeling regions that correspond approximately to ecoregions. The Forest Service's Remote Sensing Applications Center (RSAC) acquired, pre-processed, and mosaicked the Landsat ETM satellite imagery used in mapping.

Research was an important component of this project. We addressed research questions on: (1) statistical methods for spatial prediction; (2) landscape characterization (environmental and disturbance factors influencing patterns and dynamics of ecological communities); and (3) scaling and linking of vegetation maps to models of stand and landscape dynamics for regional analysis of management and disturbance effects.

The project was conducted by the LEMMA team (PNW Research Station and Oregon State University) at the Corvallis Lab, in close collaboration with the Western Wildlands Environmental Threats Assessment Center, the Interagency Mapping and Assessment Project (IMAP), Northwest Forest Plan Effectiveness Monitoring, the Remote Sensing Applications Center, and Forest Inventory and Analysis at the PNW Research Station.