Sierra Nevada forests have historically exhibited a rich diversity of structures, ranging from individual trees and dense clumps to open gaps in the canopy. This patchy arrangement is known as an ICO pattern (Individual trees, Clumps, and Openings). Forest managers now use this pattern as a model for restoring healthy forest conditions and improving resilience to wildfires and other disturbances.
To support this work, Whitebark is leveraging innovative technologies like Rx Gaming and Licosim to assess forest conditions and refine our treatment strategies for maximum effectiveness.
What Are Rx Gaming and Licosim?
Rx Gaming is a planning and visualization tool that allows forest managers to explore how different treatment strategies can affect forest resilience. Using lidar (Light Detection and Ranging) , it provides a view of current forest heterogeneity (i.e., ICO pattern) and compares it to desired conditions based on reference areas.
Lidar uses pulses of light to measure the height and density of vegetation, enabling managers to see detailed spatial patterns, such as the ICO pattern, across large landscapes. With this insight, managers can assess how closely a forest resembles a healthy, resilient structure and plan accordingly.
Rx Gaming allows users to “game out” different treatment options by adjusting variables like tree density, canopy cover, basal area, diameter caps (the limit on the size of tree that can be removed), and the size of clumps, helping to visualize outcomes and refine prescriptions before implementation.
Licosim takes this information and applies it on a landscape scale, allowing managers to see which areas have deviated most from healthy conditions and where treatments can have the most impact.
How Whitebark is using RxGaming and Licosim On-the-Ground
ICO patterns are difficult to create, as people tend to thin trees to an even spacing, even without intentionally doing so. We see this spacing as ‘neat’ and ‘organized’, while this is dramatically different from the irregular spacing that frequent fires produce on the landscape. RxGaming aids us in getting away from unintentionally creating even spacing when determining when and where to remove trees. These tools offer direction on which trees to cut and provide a guide on how often to create different features like clumps and openings and where they are best suited on the landscape.
In the planning phase, Whitebark is currently using RxGaming to both improve efficiency and plan and visualize forest thinning treatments. Traditionally, gathering measurements of current forest conditions required staff to conduct time intensive field surveys. RxGaming streamlines this process by using visual data to estimate key metrics, such as the maximum tree diameter allowed in each treatment unit to meet target basal area and trees per acre (TPA) goals.
This tool has also been used to visualize current conditions and future (modeled) treatment outcomes and compare how similar these are to reference areas. This comparison allows us to modify treatments to better meet reference conditions and ICO targets, without having to learn through actual tree cutting.
Why Does Forest Structure Matter?
Forest structure (the spatial arrangement of trees and vegetation) has a major influence on ecosystem functions such as hydrology, wildlife habitat, and resilience to fire and insect outbreaks.
Historically, frequent low- to moderate-intensity wildfires shaped the Sierra Nevada landscape, creating a mosaic of different age classes and structures. This natural variability made forests more resilient to future disturbances and contributed to the overall health of the ecosystem.
For example, a typical resilient landscape might include:
- Young tree patches regenerating after a recent fire
- Older, well-spaced trees with an open understory thinned by past low-intensity fires
- Denser corridors of vegetation in wetter areas like streams and wet meadows that fires have skipped over
Hydrology
Dense forests can negatively affect water availability by reducing snowpack retention and limiting streamflow.
- In tightly packed canopies, snow often lands on treetops and sublimates (evaporates directly into vapor) before it reaches the ground.
- Forests with more openings allow snow to accumulate on the ground and persist in the snowpack.
- Denser forests also consume more groundwater, reducing streamflow.
Studies of reference areas, where fire has been reintroduced and allowed to naturally thin vegetation, show increased year-round water flow, in contrast to declines observed in denser, fire-suppressed forests elsewhere in the Sierra. Key reference areas in the Sierra include the Illilouette Basin in Yosemite National Park and the Sugarloaf Basin in Sequioa-Kings Canyon National Park, where managed wildfire programs were established in the 1970s.
Within the Inyo National Forest, the Indiana Summit Research Natural Area serves as a valuable reference area for Jeffrey pine forest.
Resilience to Disturbance
Variation in forest structure naturally slows the spread of wildfire. Openings act as fuel breaks, creating gaps where fires can lose intensity or stop altogether. These conditions support low- to moderate-intensity fires that burn without causing widespread tree mortality.
In contrast, dense forests fuel more intense fires and facilitate the spread of pests such as bark beetles, which thrive in crowded tree stands with weakened defenses. Openings within the stand can also slow the spread of bark beetle by dissipating the pheromones that bark beetles use to communicate and attract more beetles to the stand.
Learn more from our blog post on bark beetles.
Wildlife Habitat
Just as structure affects fire and water availability, it also shapes wildlife habitat. A diverse forest structure supports a wide array of species:
- Clumps of trees provide cover and foraging habitat for species like martens and flying squirrels, which prefer shaded, closed-canopy conditions.
- Openings create space for hunting and foraging by predators like owls and hawks.
By restoring the natural mosaic of clumps, gaps, and individual trees, we can support richer biodiversity while also enhancing the forest’s ability to withstand changing climate conditions and increasing disturbances.