Malcolm P. North

Managing Forests and Fire in Changing Climates

Policy focused on fire suppression only delays the inevitable. With projected climate change, we expect to face much more forest fire in the coming decades. Policy-makers are challenged not to categorize all fires as destructive to ecosystems simply because they have long flame lengths and kill most of the trees within the fire boundary. Ecological context matters: In some ecosystems, high-severity regimes are appropriate, but climate change may modify these fire regimes and ecosystems as well. Some undesirable impacts may be avoided or reduced through global strategies, as well as distinct strategies based on a forests historical fire regime.

Fuel treatment effects on tree-based forest carbon storage and emissions under modeled wildfire scenarios.

Forests are viewed as a potential sink for carbon (C) that might otherwise contribute to climate change. It is unclear, however, how to manage forests with frequent fire regimes to maximize C storage while reducing C emissions from prescribed burns or wildfire. We modeled the effects of eight different fuel treatments on tree-based C storage and release over a century, with and without wildfire. Model runs show that, after a century of growth without wildfire, the control stored the most C. However, when wildfire was included in the model, the control had the largest total C emission and largest reduction in live-tree-based C stocks. In model runs including wildfire, the final amount of tree-based C sequestered was most affected by the stand structure initially produced by the different fuel treatments. In wildfire-prone forests, tree-based C stocks were best protected by fuel treatments that produced a low-density stand structure dominated by large, fire-resistant pines.

Standing crop and animal consumption of fungal sporocarps in Pacific Northwest forests

Although fungal fruiting bodies are a common food supplement for many forest animals and an important dietary staple for several small mammals, changes in their abundance and consumption with forest succession or disturbance have not been quantified. Above- and belowground fungal fruiting bodies (epigeous and hypogeous sporocarps) were sampled for 46 mo in managed-young, natural-mature, and old-growth western hemlock (Tsuga heterophylla) stands in Washington State. Screen enclosures were placed over the surface of half of the sample plots to prevent aboveground predation of sporocarps. Standing crop of epigeous sporocarps was low in most seasons and then increased 30-fold to a mean of 2.28 kg/ha in the fall. Epigeous biomass varied little between stand types, and animal consumption of these sporocarps was low. Standing crop of hypogeous sporocarps was 0.78 kg/ha in managed-young stands, compared to 4.51 and 4.02 kg/ha in natural-mature and old-growth stands. In all stands, standing crop peaked in the summer and was lowest in the winter. Mean animal consumption of hypogeous sporocarps was 0.64 kg/ha, a value that exceeded the available standing crop quantity of 0.36 kg/ha in managed-young stands during the winter. In natural-mature and old-growth stands, truffle biomass remained high year-round and exceeded consumption in all seasons. Low hypogeous sporocarp biomass in the managed-young stands resulted from the general absence of large clusters of Ela- phomyces granulatus, which made up >90% of the biomass in older stands. This absence in managed-young stands may be associated with the thin organic layer that has developed following harvest and burning 60 yr ago. The consistent level of animal consumption indicates that truffles may be an important and readily available year-round food source, compared to the ephemeral fruiting of epigeous sporocarps. Changes in forest composition and age due to natural disturbance or human management influence fungal sporocarp pro- ductivity and diversity and, consequently, affect food availability for animals dependent on hypogeous sporocarps.

Fire suppression and fuels treatment effects on mixed-conifer carbon stocks and emissions

Depending on management, forests can be an important sink or source of carbon that if released as CO2 could contribute to global warming. Many forests in the western United States are being treated to reduce fuels, yet the effects of these treatments on forest carbon are not well understood. We compared the immediate effects of fuels treatments on carbon stocks and releases in replicated plots before and after treatment, and against a reconstruction of active-fire stand conditions for the same forest in 1865. Total live-tree carbon was substantially lower in modern fire-suppressed conditions (and all of the treatments) than the same forest under an active-fire regime. Although fire suppression has increased stem density, current forests have fewer very large trees, reducing total live-tree carbon stocks and shifting a higher proportion of those stocks into small-diameter, fire-sensitive trees. Prescribed burning released 14.8 Mg C/ha, with pre-burn thinning increasing the average release by 70% and contributing 21.9-37.5 Mg C/ha in milling waste. Fire suppression may have incurred a double carbon penalty by reducing stocks and contributing to emissions with fuels-treatment activities or inevitable wildfire combustion. All treatments reduced fuels and increased fire resistance, but most of the gains were achieved with understory thinning, with only modest increases in the much heavier overstory thinning. We suggest modifying current treatments to focus on reducing surface fuels, actively thinning the majority of small trees, and removing only fire-sensitive species in the merchantable, intermediate size class. These changes would retain most of the current carbon-pool levels, reduce prescribed burn and potential future wildfire emissions, and favor stand development of large, fire-resistant trees that can better stabilize carbon stocks.

Reform forest fire management

Agency incentives undermine policy effectiveness Globally, wildfire size, severity, and frequency have been increasing, as have related fatalities and taxpayer-funded firefighting costs (1). In most accessible forests, wildfire response prioritizes suppression because fires are easier and cheaper to contain when small (2). In the United States, for example, 98% of wildfires are suppressed before reaching 120 ha in size (3). But the 2% of wildfires that escape containment often burn under extreme weather conditions in fuel-loaded forests and account for 97% of fire-fighting costs and total area burned (3). Changing climate and decades of fuel accumulation make efforts to suppress every fire dangerous, expensive, and ill advised (4). These trends are attracting congressional scrutiny for a new approach to wildfire management (5). The recent release of the National Cohesive Wildland Fire Management Strategy (NCWFMS) (6) and the U.S. Forest Services (USFSs) current effort to revise national forest (NF) plans provide openings to incentivize change. Although we largely focus on the USFS, which incurs 70% of national firefighting costs (7), similar wildfire policies and needed management reforms are relevant throughout the United States and fire-prone areas worldwide.

Restoring fire-prone Inland Pacific landscapes: seven core principles

ContextMore than a century of forest and fire management of Inland Pacific landscapes has transformed their successional and disturbance dynamics. Regional connectivity of many terrestrial and aquatic habitats is fragmented, flows of some ecological and physical processes have been altered in space and time, and the frequency, size and intensity of many disturbances that configure these habitats have been altered. Current efforts to address these impacts yield a small footprint in comparison to wildfires and insect outbreaks. Moreover, many current projects emphasize thinning and fuels reduction within individual forest stands, while overlooking large-scale habitat connectivity and disturbance flow issues.MethodsWe provide a framework for landscape restoration, offering seven principles. We discuss their implication for management, and illustrate their application with examples.ResultsHistorical forests were spatially heterogeneous at multiple scales. Heterogeneity was the result of variability and interactions among native ecological patterns and processes, including successional and disturbance processes regulated by climatic and topographic drivers. Native flora and fauna were adapted to these conditions, which conferred a measure of resilience to variability in climate and recurrent contagious disturbances.ConclusionsTo restore key characteristics of this resilience to current landscapes, planning and management are needed at ecoregion, local landscape, successional patch, and tree neighborhood scales. Restoration that works effectively across ownerships and allocations will require active thinking about landscapes as socio-ecological systems that provide services to people within the finite capacities of ecosystems. We focus attention on landscape-level prescriptions as foundational to restoration planning and execution.

Microhabitat analysis using radiotelemetry locations and polytomous logistic regression

Microhabitat analyses often use discriminant function analysis (DFA) to compare vegetation structures or environmental conditions between sites classified by a study animals presence or absence. These presence/absence studies make questionable assumptions about the habitat value of the comparison sites and the microhabitat data often violate the DFAs assumptions of an equal covariance structure and multivariate normality. An alternative is to generate an ordinal measure of site-use intensity from radiotelemetry locations. This measure is derived from the percentage of total telemetry points of a study animal that are found at use-only sites, overcoming many of the problems associated with defining absence sites. The use-intensity response is then modeled as a function of microhabitat variables using ordered polytomous logistic regression (PLR). Unlike DFA, PLR does not require covariance equality or multivariate normality, and allows categorical microhabitat variables. The classification error of the microhabitat model developed with PLR is then assessed by jackknifing. This technique is demonstrated with an example analysis of the foraging microhabitat of the northern spotted owl (Strix occidentalis caurina). The resulting model correctly classified 78% of the sample stands in the jackknife evaluation. For animals with site fidelity and radiotelemetry data, the proposed technique may provide a robust alternative for microhabitat analysis.

Vegetation and ecological characteristics of mixed-conifer and Red Fir forests at the Teakettle Experimental Forest

References Anonymous. 1970. Recommendations for an international standard for a mapping method in bird census work.

Water transfer via ectomycorrhizal fungal hyphae to conifer seedlings

Little is known about water transfer via mycorrhizal hyphae to plants, despite its potential importance in seedling establishment and plant community development, especially in arid environments. Therefore, this process was investigated in the study reported in this paper in laboratory-based tripartite mesocosms containing the shrub Arctostaphylos viscida (manzanita) and young seedlings of sugar pine (Pinus lambertiana) and Douglas-fir (Pseudotsuga menziesii). The objectives were to determine whether water could be transported through mycorrhizal symbionts shared by establishing conifers and A. viscida and to compare the results obtained using two tracers: the stable isotope deuterium and the dye lucifer yellow carbohydrazide. Water containing the tracers was added to the central compartment containing single manzanita shrubs. The fungal hyphae were then collected as well as plant roots from coniferous seedlings in the other two compartments to determine whether water was transferred via fungal hyphae. In addition, the length of the hyphae and degree of mycorrhizal colonisation were determined. Internal transcribed spacer–restriction fragment length polymorphism (ITS-RFLP) analysis was used to identify the fungal species involved in dye (water) transfer. Results of the stable isotope analysis showed that water is transferred via mycorrhizal hyphae, but isotopically labelled water was only detected in Douglas-fir roots, not in sugar pine roots. In contrast, the fluorescent dye was transported via mycorrhizal hyphae to both Douglas-fir and sugar pine seedlings. Only 1 of 15 fungal morphotypes (identified as Atheliaceae) growing in the mesocosms transferred the dye. Differences were detected in the water transfer patterns indicated by the deuterium and fluorescent dye tracers, suggesting that the two labels are transported by different mechanisms in the same hyphae and/or that different fungal taxa transfer them via different routes to host plants. We conclude that both tracers can provide information on resource transfer between fungi and plants, but we cannot be sure that the dye transfer data provide accurate indications of water transfer rates and patterns. The isotopic tracer provides more direct indications of water movement and is therefore more suitable than the dye for studying water relations of plants and their associated mycorrhizal fungi.

Influence of light and soil moisture on Sierran mixed-conifer understory communities

Sierra Nevada forests have high understory species richness yet we do not know which site factors influence herb and shrub distribution or abundance. We examined the understory of an old-growth mixed-conifer Sierran forest and its distribution in relation to microsite conditions. The forest has high species richness (98 species sampled), most of which are herbs with sparse cover and relatively equal abundance. Shrub cover is highly concentrated in discrete patches. Using overstory tree cover and microsite environmental conditions, four habitats were identified; tree cluster, partial canopy, gap, and rock/shallow soil. Herb and shrub species were strongly linked with habitats. Soil moisture, litter depth and diffuse light were the most significant environmental gradients influencing understory plant distribution. Herb cover was most strongly influenced by soil moisture. Shrub cover is associated with more diffuse light, less direct light, and sites with lower soil moisture. Herb richness is most affected by conditions which influence soil moisture. Richness is positively correlated with litter depth, and negatively correlated with direct light and shrub cover. Disturbance or management practices which change forest floor conditions, shallow soil moisture and direct light are likely to have the strongest effect on Sierran understory abundance and richness.