Background

There has been recent interest in producing maple syrup from big leaf maple (Acer macrophyllum) trees located in riparian zones in Washington state. Potential sites require a mininum number of big leaf maple trees at least eight inches in diameter (DBH). Preferred sites also have a proximity to roads and power. Using the 2019 Washington State Forestland Database we identified every potential site that met the minimum criteria of 250 taps within a 4 acre area. A web map was developed with the potential site locations and reference layers.

NRSIG is working with CINTRAFOR on part of this larger project:

Maple Syrup Production from Big Leaf Maple Trees in the Riparian Zones of Washington's Forests

University of Washington will conduct a three-year research project to determine the best practices to facilitate the development of a commercial maple syrup industry in the Pacific Northwest (PNW), specifically in Washington State. The project objectives involve determining the volume of sap and syrup that can be produced according to the following variables: (1) Different elevations, latitude, and climatic zones (2) Collection methods using traditional bucket collection versus high vacuum tubing systems, (3) Size and health of bigleaf maple trees, and (4) Timing of tapping and strategies such as reaming of existing tap holes or re-tapping trees throughout the season (December-March). The research will also provide educational opportunities on how to develop the most successful and cost-effective sugaring enterprises with bigleaf maple in the PNW to bring additional income and diversity to the region’s farming and forestry operations. 

Our Work

Gradient Nearest Neighbor (GNN) tree lists were summarized to calculate the number of big leaf maple trees per acre by diameter size class. Sizes classes were determined by the number of taps a tree could support. The smallest size class, from 8 to 15 inches, supports one tap. Every five additional inches of diameter supports one additional tap. The largest tree in the dataset was 98.9 inches. The number of taps per tree was multiplied by the trees per acre and summed across all size classes to calculate the number of taps per acre each GNN inventory represents.

A GNN raster layer links tree lists to locations in the state. Using this reference raster and the GNN tree list summary results, a new raster of taps per acre was created. The resolution of this raster was 104.355 feet (1/4-acres per cell). This raster was generalized to one-acre and four-acre cells by averaging cells in a 2-by-2 and 4-by-4 cell neighborhood, respectively. Potential sites were identified as those four-acre raster cells with at least 50 taps per acre and at least 250 taps per cell.

The potential sites were converted to polygons and intersected with other layers of interest. Owner class, county, WRIA, and WAU were determined using the Washington State Forestland Database. Zonal statistics were used to calculate the average slope and elevation using a 30-meter digital elevation model from the Washington State Department of Natural Resources and annual precipitation from PRISM data (PRISM Climate Group, 2012). A proxy for electricity availability was developed from land use code and improvement value data in the Washington State Forestland Database. Parcels with a developed land use code (< 70) or improvement value > 0 were assumed to have electricity. Sites were intersected with the parcel subset to determine electricity availability.

Results

Over 19,000 potential sites were identified in Washington. The largest number of sites were located in King County, followed by Snohomish, Skagit, Whatcom, and Kitsap counties. Sites in King County also had a slightly higher density of potential taps per site compared to other counties. The variance in the number of sites per county was large, while the variance in the density of taps per site was small. 

Deliverables

MapleSyrup_WAUPages_IndexMap.pdf

MapleSyrup_WAUPages.pdf

Big Leaf Maple Syrup Site Potential Online Web Map

Instructions for installing and using the Maple Syrup Web Map on a mobile device

MapleSyrup_Sites.xlsx