A significant outcome of this research lies in its broader implications for forest stewardship. This study recognizes the importance of incorporating Indigenous perspectives—particularly those of the Northern Pomo, the original stewards of these lands—into the responsible management of keystone species such as tanoak. For millennia, Indigenous Californians actively shaped redwood–tanoak ecosystems through intentional and frequent use of fire, sustaining food resources, promoting desired stand conditions, and limiting hazardous fuel accumulation. Tanoak remains culturally central to the Pomo people as a primary food source, emphasizing the need for genuine, collaborative partnerships in future management and research efforts. Integrating Indigenous fire stewardship with contemporary forest management represents not only a pathway toward the practice of pyrosiviculture, but also an essential step toward respectful and sustainable land stewardship.

The simple method we used probably over-estimated vegetation fuel loading, evidenced by the fact that the large fuel loading differences measured for the vegetation class are not reflected in the increase in fine fuels following PCT. Although the contribution of slash foliage is not accounted for, it appears our method may have over predicted vegetation loading by around a factor of three under the assumption that the majority of the difference in vegetation fuels should be captured by the sum of the differences in fine fuels.

Limitations and future work

Duff and litter are not reported for post-pct stands for two reasons. First, these are not expected to have changed significantly given the relatively short timespan before and after PCT. Second, our sampling protocol did not make it clear how to quantify the loading for leaves attached to recently cut branches, especially given that these “suspended litter” particles were in a state of active transition to the ground, as they dry, abscise, and sift through the coarser woody fuels as they make their way to the ground. This class may deserve more attention because of it’s potentially dynamic relationship with the timing of prescribed fires: as suspended particles settle and begin to decompose they’re bulk density changes and bulk density is an important determinant of fire behavior.

live and dead vegetation components were combined

every redwood leaf-spray

That young forest

ollowing previous studies that found similar bulk densities for duff and litter

Sprout height

:

statistically supported

Rapidly developing redwood and tanoak sprouts will likely further compromise Douglas-fir seedlings competitive ability.

Douglas-fir

counts

Additional uncertainty may be due to variable light levels within macro plots.

north and south facing slopes

redwood growth

saw

much more dramatically

Discussion

It is important to point out here that the HA and HD “high-density” treatments in this experiment only targeted a residual overstory relative density of 20% (that is 20% of assumed total carrying capacity of the site), and this was selected as an upper limit to support the objective of maintaining conifer growth (Berrill & O’Hara, 2009).

Our use of basal area as a response did not distinguish between number of stems and size of stems. There have been numerous metrics used in attempts to assess shade tolerance (Forrester et al., 2014). Our use of basal area (which conflates growth and survival of sprouts) is justified given the assumption that these are expected to be correlated in forests that do not undergo a long harsh winter (Lin et al., 2002).

Basal area was selected as the metric for quantifying redwood and tanoak abundance because prolific sprout regeneration in both species was undergoing self-thinning. In this context, basal area provided a more informative measure than stem density, as it better captured treatment responses by reflecting the relative contribution of established stems rather than the transient abundance of sprouts.

3.3.3 Pre-post commercial thinning comparison

Table 3.11: P

For Duff & Litter, the largest difference was between the HD and HA treatments. The HD treatment had about 54.4 Mg ha-1, and was about 14.39 Mg ha-1 greater than the HA treatment (p = 0.09). Generally, all treatments were similar, with estimated loading of around 47 Mg ha-1.

able 3.5:

Basal area

Table 3.4:

Expected marginal means

Counts of rege

Figure 3.2 shows the same model as Figure 3.1, but with an emphasis on treatment comparisons between redwood and tanoak. This shows that we expect on average, 7.88 m2 ha-1 greater redwood basal area than tanoak basal area in the GS treatment (p = 0.1), about 1.69 m2 ha-1 in the LD treatment (p = 0.4), and about 0.6 m2 ha-1 in the HA treatment (p = 0.48). In the HD treatment, we expect to see slightly higher tanoak basal area (p = 0.55).

Pairwise comparisons

Table 3.2: Basal area (m2 ha-1) modeled at the vegetation plot level for four harvest treatments and four species classes (n = 16). The asymptotic 95% confidence intervals are based on the normal approximation.

Redwood regeneration basal area showed the greatest treatment response. The GS treatment had the greatest basal area of redwood regeneration at 10.12 m2 ha-1, which was 9.28 m2 ha-1 greater than in the HD treatment (p = 0.19). The LD and HD treatments were intermediate. Tanoak regeneration basal area was intermediate between that of redwood and Douglas-fir and other species. The GS and LD treatments had similar responses, as did the HA and HD treatments. The GS treatment resulted in 2.24 m2 ha-1 of tanoak basal area, which was 1.33 m2 ha-1 greater than in the HA treatment (p = 0.18). On average, for Douglas-fir, we expect about 0.17 m2 ha-1 of basal area across treatments. The greatest basal area of Douglas-fir was in the GS treatment which was 0.12 m2 ha-1 greater than in the HA treatment (p = 0.76). The LD, HA, and HD treatments were all comparatively similar. Other species included grand fir, madrone, and California wax-myrtle, of which there was a total of 23, 28, and 16 observations across our 16 macro plots (comprising 64 tree density plots). Generally, each plot had between 0 and 9 observations of other species, except for one macro plot with the LD treatment, which had 16 observations (data not shown). According to predictions made from this model for other species, there was not enough evidence to confirm a statistically significant difference between treatments. On average, we expect about 0.11 m2 ha-1 of basal area across treatments. The greatest basal area of other species was in the HD treatment which was 0.12 m2 ha-1 greater than in the HA treatment (p = 0.26). The GS and LD treatments were intermediate.

The formulas below use β to represent fixed effects and α to represent random effects. Subscripts indicate the variable associated with each effect. Superscripted Greek letters indicate the model component where fixed or random effects are present in more than one component (e.g., μ for the conditional model, π for the hurdle model, and ϕ for the dispersion model). A “hurdle gamma” distribution is used for models of basal area and fuels and is defined below.

GLMMtmb,

duff and litter fuels

Akaike information criterion, Bayesian information criterion

live

, though,

This decision makes explicit instances when when fuels are vertically continuous with the ground.

when

during pre-PCT measurements

four-meter

Figure 2.1:

Northern

Therefore, the objective of this research was to quantify the development of live surface fuels–the forest understory–as well as dead surface fuels by size class and their dynamics with regard to a PCT fuels treatment with potential to reduce fire severity. And to measure these within the context of a multiaged silvicultural system under a range of residual overstory densities to explore trade offs between overstory retention, new sprout development, and surface fuel management.

1.4 Pyrosilviculture

indigenous

my

To our knowledge, no studies have examined the flammability of live tanoak foliage or tanoak sprouts.

Harvesting techniques designed to promote productivity (like GS, LD) resulted in significantly greater redwood growth and height. However, these same techniques also produced higher levels of live vegetation fuels pre-PCT and, consequently, higher volumes of fine dead fuels (10-hr and 100-hr) immediately following the PCT fuels treatment.

need data