Integrating Climate Change into Reforestation Strategy for the Mendocino National Forest

The recent devastating wildfires in the Mendocino National Forest (MNF) have presented a formidable challenge for management efforts and highlighted the urgent need for a comprehensive reforestation strategy. To address this, the Clear Lake Environmental Research Center (CLERC) partnered with Dr. Steven Greco from the University of California, Davis to examine the issue. The study, titled Informing Reforestation Strategy for the Mendocino National Forest: Integrating Climate Change into Management Planning of the North Shore Restoration Project (NSRP), aimed to guide future land management decisions in the MNF. The study employed geographic information system (GIS) technology to analyze biophysical site conditions and develop a site capability model and map for the NSRP area, encompassing approximately 40,000 acres.

Understanding the Challenge

The widespread wildfires, including the Mendocino Complex Fire in 2018, have created a critical need for landscape-scale analysis and planning to restore the MNF to its desired conditions. This includes reforestation efforts that promote ecological resilience and adaptability to future fire regimes and changing climate dynamics. The study emphasizes the importance of prioritizing restoration management activities and addresses the impact of climate change on the potential success of reforestation efforts.

The Approach

The study employed geographic information system (GIS) technology to analyze biophysical site conditions and develop a site capability model and map for the NSRP area, encompassing approximately 39,300 acres. A "land facet" approach was used to divide the landscape into logical land management units based on key ecological factors. These factors included the vulnerability of pre-fire vegetation communities to climate change, exposure based on topography, burn severity, and soil type.

Typical post-fire conditions in the North Shore Restoration Project area, October 22, 2020.

Figure 31: Mixed conifer (SMC) is shown in relation to soil AWS Class 5 with the planting recommendations. There are numerous polygons for replanting opportunities (see yellow areas) within soil AWS Class 5. SMC polygons that reflect planting recommendation #3 (red areas) may be able to be planted with Ponderosa Pine (PPN). Source: Informing Reforestation Strategy for the Mendocino National Forest: Integrating Climate Change into Management Planning of the North Shore Restoration Project (NSRP)

Planting Recommendations

The analysis resulted in the creation of a map depicting 27 unique combinations of the three main variables: vulnerability, exposure, and burn severity. Expert opinion was then used to assess each combination and provide a planting recommendation. The three possible recommendations were: (1) allowing natural regeneration, (2) replanting with pre-fire plant species, and (3) introducing new species due to expected shifts in plant community types caused by climate change. The study found that approximately 47% of the NSRP site should be left for natural regeneration, 18% should be replanted with pre-fire species, and 35% should undergo a shift in plant community type.

Prioritizing Planting Efforts

To refine the planting recommendations, the study considered the fourth variable: available water storage (AWS) in the soil. Areas with deeper soil and higher AWS were identified as the highest priority for replanting, as they offer better resistance to climatic water deficits. Priority decreased as AWS decreased, with areas having the thinnest soils assigned the lowest priority for reforestation.

Considering Future Conditions

Given the severity of recent fire effects and the anticipated impacts of climate change, the study acknowledged that some areas may not support the same or similar plant communities in the future. These areas, where "type conversions" of plant communities are expected, were identified for the development of better-adapted plant species and communities. For example, areas where conifers were once dominant may transition to oak woodlands, benefiting from localized management efforts to enhance oak woodland resources.

By 2024, the unmanaged portion of the project contains substantial amounts of naturally regenerating knob cone pine.

Plant Species Selection

To aid land managers in selecting specific plant species for reforestation, a database was created, linking various vegetation community classification schemes to individual species. By integrating data from the California Wildlife Habitat Relationship (CWHR) system and the California Native Plant Society's Manual of California Vegetation (MCV) system, the database provides a tool for identifying not only dominant species but also other associated species within a community type.

Limitations and Recommendations

The study acknowledges some limitations, including the lack of field testing and validation of the planting recommendations and the potential errors in mapping variables. The authors recommend undertaking a validation study to confirm the high priority areas for restoration. Additionally, verifying each mapping variable is crucial to ensure accurate prescription for reforestation efforts.

Conclusion

The study provides valuable insights and recommendations to inform reforestation strategies for the Mendocino National Forest. By integrating climate change considerations, prioritizing planting efforts based on site conditions, and guiding the selection of plant species, the study offers a comprehensive approach to restoring the forest's ecological health and resilience. While further validation and field testing are necessary, the findings lay a solid foundation for effective and adaptive reforestation management in the Mendocino National Forest.

The information and insights gleaned from this study are critically important for the MNF and CLERC as we work towards restoring the forested landscape lost during the Ranch Fire in 2018. It’s a known fact that many of the forests that we’ve lost to wildfire in the last decade were established during cooler, wetter times. Due to the changing climate becoming hotter and drier, the species composition of restored forests will be different in the future. The Greco study helps inform replanting decisions regarding species selection, so that restoration efforts today can take into account likely future conditions and have a greater chance of success over the long term.

Check out the full study if you'd like to learn more.