Introduction

The Olympic Experimental State Forest Type 3 Watershed Study has developed novel forest treatments to be implemented and studied over the coming decades. The spatial arrangement of trees is an important component of the silvicultural prescriptions. This poses a challenge for developing reliable growth and yield projections with existing, distance-independent growth models such as the Forest Vegetation Simulator (FVS).

This project addresses the challenge by applying FVS using an equally novel approach. For treatments with a strong spatial component, stem maps of representative acre(s) are created with explicit tree locations. These maps are divided into plots that are grown in FVS. Prior to each growth cycle, the light environment is characterized for each plot based on neighboring plot top heights. Growth multipliers are then applied to adjust the growth projections.

This project produced growth and yield predictions for the Ethnoforestry Variable Planting Density (EVPD), Complex Early Seral (CES), and Advanced Variable Density Thinning (AVDT) experiments. Results for CES and AVDT are compared to simulations for the Standard Variable Retention Harvest (SVRH) and Standard Variable Density Thinning (SVDT), respectively. Ethnoforestry Variable Ratio Polyculture (EVRP), which can be modeled using a standard FVS approach, is also reported.

Methods

Stem maps were created based on initial forest inventory and/or the novel treatment prescriptions. Each stem map was divided into plots that were individually growth in FVS. Between growth cycles, FVS was stopped, a canopy surface raster was generated, and a solar radiation was calculated for each plot using the solar radiation tool in ESRI ArcGIS. FVS growth modifiers were developed to adjust growth based on the amount of solar radiation received.

To calibrate the growth modifiers, we studied data from the Capitol Forest Silvicultural Options Study. This study implemented treatments with a variety of forest floor light conditions including clearcut, uniform thin, and creation of small and large gaps. The study also included lidar acquisitions coincident with plot measurements and 20-year remeasurement data. The study improved our ability to quantify the growth modifications used in the OESF Type 3 Watershed Study.

Results

Example results are provided for the CES treatment. The image shows average height and basal are per acre for the CES and standard variable retention harvest treatments for each plot at age 10, 30, and 50 from overhead perspective. The results show the shading effects on the north side of small and large clumps resulting in increased heterogeneity in the CES treatment for the reported attributed over time. Standard growth and yield outputs indicate the tradeoffs in volume and stand structure metrics between the DNR standard and novel treatments.

Deliverables

OESF Type 3 Watershed G-Y Project Report 20240117.pdf

Type3_FVS_Simulations.zip