Christopher R. Keyes

Influences of moisture content, mineral content and bulk density on smouldering combustion of ponderosa pine duff mounds

When applying prescribed fire to long-unburned but fire-adapted ecosystems, fuels managers require better decision-support models to determine appropriate conditions for achieving desired effects. Prolonged combustion in duff accumulations at the base of large conifers may lead to fine root mortality, cambial injury, enhanced susceptibility to bark beetle attack, and possibly tree death. A laboratory experiment was conducted to investigate how moisture content, mineral content, and bulk density affect smouldering combustion in ponderosa pine (Pinus ponderosa C. Lawson) duff mound fuels of the south-eastern Klamath Mountains, California, USA. Samples were divided between upper and lower duff for a total of 100 burn tests. Moisture content was adjusted to observe the transition through the ignition and spread limit. Bulk density, mineral content and percentage consumption were recorded for each burn. The moisture content threshold for smouldering combustion was 57 and 102% respectively for upper and lower duff. Percentage consumption was inversely related to moisture content for both layers of duff, and partially dependent on mineral content for lower duff. Bulk density was a non-significant factor in either ignition or percentage combustion for the conditions examined here. Results from this study identify important attributes of duff that control the burning process in order to inform prescribed burning decisions.

Observed dynamics of ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) seedling recruitment in the Cascade Range, USA

An observational study of early seedling establishment (first 1–2 summers after emergence) was conducted in four ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) stands east of the Cascade Range crest in central Oregon, USA. Newly emerged ponderosa pine seedlings were identified at the start of summer and were monitored through their second summer; a subsequent cohort of seedlings was identified and monitored for one summer. About 3% of the viable seed that was produced resulted in new seedlings. Mortality was substantial immediately following emergence. Most seedlings emerged without shading from understory vegetation, but few survived. Most seedlings alive after one year had emerged beneath live cover; by the end of two summers only shaded seedlings were alive. 63–85% of new seedlings initiated in clusters attributed to rodent caching, and seedlings originating in clusters remained a substantial proportion of the cohort (60%) after two seasons. Results suggest that understory vegetation in these types of stands facilitates the recruitment of ponderosa pine seedlings, most likely by buffering them against environmental stressors during the seedling establishment phase. They also reveal that seed caching rodents are highly active in seed redistribution and can exert a lasting influence on seedling recruitment.

Montana logging machine rates

Montana’s logging industry has changed significantly over the past two decades. Increased operating costs and subsequent diminishing returns, combined with a shifting paradigm in regards to active forest management have had significant impacts on the economic and demographic make-up of the industry. One way to address these changes and mitigate the associated challenges of continued viability is through analysis of the factors and constraints impacting routine operational costs. To provide a resource for comparison between commonly-utilized logging equipment, the hourly owning and operating costs of select mechanical, ground-based machines were calculated using the machine rate method from data supplied by western Montana equipment dealers. The results were compared to historical cost data, and reasons for increased logging expense were studied and discussed. Inflation-adjusted operating costs for ground-based equipment appear to be 32–86% higher than 20 years ago. Reasons include increases in equipment purchase price, fuel, labor wages and benefits, and repair/maintenance expenses as well as a decrease in the number of operational days per year.

Early-Stage Thinning for the Restoration of Young Redwood—Douglas-Fir Forests in Northern Coastal California, USA

Among forested parks and reserves of the Pacific Coast of the United States, the restoration of late-successional conditions to second-growth stands is a management priority. Some traditional silvicultural treatments may help achieve this objective. We evaluated early-stage thinning as a restoration treatment to facilitate the growth and development of young (33- to 45-year old), homogeneous, and second-growth stands of coast redwood (Sequoia sempervirens) and Douglas-fir (Pseudotsuga menziesii). Targeting both stand-level responses and dominant (focal) tree responses for analysis, we compared structural attributes of adjacent thinned and unthinned stands, 12–17 years after thinning. Thinned stands displayed enhanced metrics of tree vigor, growth, and mechanical stability, thereby improving response to future restoration treatments and broadening the range of potential stand conditions. We conclude that early-stage thinning has been successful as a preliminary restoration treatment because it accomplished many initial goals of forest restoration, while retaining sufficient tree numbers to buffer against possible attrition from future disturbances.

Seed rain of ponderosa pine beneath partial overstories

An analysis was conducted of the 1999 ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) seed crop at two stands of differing overstory density in each of two sites that differed in productivity (forest community series) on the east slope of the Cascade Range in central Oregon, USA. A total 2,166 viable seeds were collected between 2 September 1999 and 6 June 2000. Total seed quantities varied more by site than by tree density, with the xeric site producing six-fold greater seed yields. Within each site, the stand of higher density produced more viable seed. Per-tree cone yields were also greater at the site of lesser productivity. At three of the four stands, tree fecundity (as measured by cone counts) was positively related to diameter at breast height and height, but not to live crown ratio. A difference in temporal seedfall patterns among the two sites occurred late and was relatively minor: most seedfall occurred within the first month after it started regardless of absolute seed production. Seedfall distribution varied spatially within stands, but no seed trap (of 55) received less than an equivalent 28 thousand seeds per hectare. Seedfall was not perceived to be a limiting factor on natural regeneration at any of the four partial-overstory stands in this study.

A comprehensive guide to fuel management practices for dry mixed conifer forests in the northwestern United States: Inventory and model-based economic analysis of mechanical fuel treatments

Implementing fuel treatments in every place where it could be beneficial to do so is impractical and not cost effective under any plausible specification of objectives. Only some of the many possible kinds of treatments will be effective in any particular stand and there are some stands that seem to defy effective treatment. In many more, effective treatment costs far more than the value of treatment benefits. Understanding the scope of the fuel management challenges in these forests is the first step towards identifying fuel treatment approaches that are likely to be both effective and economically feasible (e.g., self-supporting) in reducing fire hazard.

Application of mathematical models in the spatial analysis of early tree seedling distribution patterns within a treefall gap at Gwangneung Experimental Forest, Korea

A spatial analysis was conducted on the characteristics of seedling recruitment and one-year mortality of two temperate deciduous tree species: Quercus serrata Thunb. ex Murray (QUSE) and Carpinus laxiflora (Siebold & Zucc.) Blume (CALA). A systematic grid of 64 seedling plots was established within a typhoon-induced treefall gap in a rare old-growth deciduous stand at Gwangneung Experimental Forest, South Korea. Inverse model, Ripley’s K function, and semivariogram tools were introduced to examine spatial relationships among seedling recruitment, one-year seedling mortality, and trees. Overall QUSE germinant density more than tripled that of CALA. Results suggest that dispersal patterns differ between the two species: for QUSE, 2Dt model yielded the best fit whereas the lognormal model was best fitted to CALA. Those differences may reflect different regeneration strategies between the two species. One-year mortality rates were similar for QUSE (76.15%) and CALA (72.25%). Mortality for both species exhibited substantial variance that was indicated as autocorrelation by the semivariogram, suggesting that mortality was not random for either species. Tree spatial patterns were also shown to be autocorrelated. Together, the observed spatial patterns in germination and first-year mortality indicate that the single treefall gap is among the factors that maintain the community structure associated with this forest type.

Thinning Promotes the Restoration of Branch Structure in Second-Growth Redwoods at Redwood National Park

as agronomy, soil science, microbiology, bio-chemistry, forestry, ecology, analytical chemistry and genetic engineering, an integrated approach can be developed to study the functional basis of chemically‒mediated rhizospheric interactions. Future studies in chemical rhizospheric ecology will open new directions for better exploitation of all beneficial soil bacterial communities (methanotrophs, PGPR, cyanobacteria, salt tolerant bacteria, etc.). In this direction modern research on ‘omics’ technologies will help to develop the plant-microbe based combined technology for the restoration of sodic soil. The use and release of genetically manipulated plants and bacteria should be considered for sodic soil restoration after ecological risk assessments.

Some Shrub Shading Effects on the Mid-Summer Microenvironment of Ponderosa Pine Seedlings in Central Oregon

Recent studies of natural regeneration dynamics in ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) forests of central Oregons Cascade Range reveal positive associations between shrubs and the survival of new tree seedlings. To shed light on the potential mechanisms of this possible facilitative relationship, we conducted a simple experiment in which ambient air temperature, relative humidity, soil temperature, and shrub-canopy light penetration were recorded beneath shrub-shaded and shrub-free locations during a typical mid-summer day in four stands at two sites. Air temperature and relative humidity were unaffected by shrubs, but soil temperatures were 6.2 °C to 6.6 °C lower beneath shrubs between 12 pm and 4 pm. Percent shading by shrubs averaged 2.3 to 3.0 times that of adjacent shrub-free locations. Amelioration of midday soil temperature appears to be one of the mechanisms involved in theorized shrub-seedling facilitations in this region.

Early Precommercial Thinning of Redwood Sprout Clumps: Evaluation of Four Techniques

Abstract Redwood (Sequoia sempervirens (D. Don) Endl.) responds favorably to sprout clump thinning in clearcut environments, but appropriate silvicultural techniques for this practice have not been developed. Four power tools for this unique application were evaluated: standard mid-sized chainsaw (long saw), small arborist chainsaw (short saw), power hedge trimmer, and a customized power brushcutter. Linear mixed effects model analysis was conducted to determine tool differences in clump processing speed, transit time, cycle time, and worker difficulty (peak heart rate). Machine costs and unit production costs were calculated separately for each tool, and perceived ease-of-use by workers was noted. Clump difficulty (sprout clump size) was a strong determinant of processing time and affected the performance of each tool differently. The long saw performed well across the range of clump difficulties but forced the highest heart rates in operators and was the most costly. The short saw was especially proficient on easy to moderate clumps, was among the least difficult, and was the least costly; it was the clear favorite for easy clumps. The hedge trimmer was among the fastest and least difficult, but its capability was constrained by sprout caliper. The brushcutter’s lackluster performance and several inadequacies prevent its recommendation. Regardless of tool selection, the condition of the sprout clump is a factor that must be taken into consideration since it strongly affects average production rates (clumps processed per productive machine hour) and area costs. Sprout age and clump size should guide tool selection, but should also be considered by operators in selectively choosing a subset of crop stumps for sprout clump thinning.