Surveys to detect damage on forested lands occur annually across the United States. Historically, much of these data have been collected by observers in aircraft documenting visible damage using a technique known as aerial detection survey (ADS) or sketchmapping. ADS is an efficient method but produces coarse scale data. We used one meter natural color imagery to conduct a photo interpretation survey (PIS) to compare the resulting data with the annual ADS data. The study area consists of a portion of the Black Hills National Forest that is currently experiencing mountain pine beetle-induced conifer mortality. Ground plots were used to compare how accurately each survey method delineated forest damage and results indicate a statistically significant difference (alpha 0.05) between ADS and PIS and a trend toward no significant difference when a buffer is considered. Substantial differences in the average size of polygons, total number of polygons, and total area mapped were observed. Our results indicate that current estimates of mortality intensity in our study area are low and remedies should be investigated. Photo surveys over the Black Hills National Forest are less efficient but yield damage polygons with higher accuracy and with fewer errors of commission than traditional ADS.
Stem-snapping frequency and species differences were assessed in similar to 30-year-old mid-elevation mixed-species plantations after a winter with above average, but not extreme, snowfall. Snapping (occurring between breast height and mid-crown) was not common (5/acre) but could be considered significant, depending on specific objectives and planning horizons. Black oak (Quercus kelloggii) snapped most often, especially compared with giant sequoia (Sequoiadendron giganteum), which did not snap at all. Ponderosa pine (Pinus ponderosa), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii) did not snap in proportions greatly different than prestorm densities. Snapped conifers tended to have greater height/diameter ratios than nonsnapped trees, but diameter ratios in these maturing plantations were generally low, probably a product of previous thinning treatments. Stem snaps could diminish or enhance objectives for modern mixed species plantations, suggesting the need for further study.
Stem injections of insecticides are generally regarded as a safer and a more environmentally friendly option (compared to foliar sprays) for protecting high-value trees against insects in sensitive areas or near homes. We carried out a three year study to determine the efficacy of trunk injections of emamectin benzoate for protection of foliage of three common host species attacked by the western spruce budworm, Choristoneura occidentalis Freeman (Lepidoptera: Tortricidae)., Defoliation by C. occidentalis was significantly reduced by nearly half over a 3-year period on treated compared to control grand fir, Douglas-fir, and alpine fir. Reduction of defoliation was comparable to standards used for aerial spraying (e.g., 50%) of conifer feeding budworms in Canada.
Estimates of large dead and down woody material biomass are used for evaluating ecological processes and making ecological assessments, such as for nutrient cycling, wildlife habitat, fire effects, and climate change science. Many methods are used to assess the abundance (volume) of woody material, which ultimately require an estimate of wood density to convert volume to biomass. To assess wood density and decomposition rate, this study examined in situ wood density of lodgepole pine logs at the Tenderfoot Creek Experimental Forest, central Montana, 1 and 11 years after felling. Wood density decreased from 0.39 g cm(-3) to 0.35 g cm(-3) over 10 years and the single exponential decay rate was 0.0085 yr(-1). A common 5-category decay classification system was evaluated for estimating wood density by decay class; however, the relationship was only partially significant.
Campfire bans are common in national forests, especially during conditions of high fire danger as managers seek to minimize the potential for wildfire, yet the importance of campfire availability to the camping decision process is less understood. A stated preference approach via an online panel survey was used to examine campsite preferences of recent national forest visitors residing in the western United States. The importance of a campfire relative to five other developed campsite attributes (campground host presence, campsite cost, availability of picnic tables, restroom facilities, and recreational vehicle (RV) hookups at the campsite) is examined. While all six site-specific attributes had a significant impact on consumer utility (P < 0.01), a campfire was the most important of the six site attributes. Overall, respondents valued a campfire as part of their campsite decision process. This offers a challenge for national forest managers, who must carefully balance the conflicting objectives of forest health and public use concerns.
Changes to summer low flows from forest harvesting were measured for a gauged fourth-order stream in the Hinkle Creek Paired Watershed Study. At the gauged stream, August streamflow increased an average of 1.9 mm/year (45%) for the three summers following forest harvest of 13% of a 1,084 ha watershed. Following a second harvest of an additional 13% of the watershed the August streamflow increased by 4.5 mm (106%) the first summer and 2.0 mm (47%) the second summer. Master recession curves were fit to the gauged watersheds and the resulting recession coefficients were used to predict low flows from small watersheds nested within the gauged watersheds. The estimated low flows were used to evaluate changes in summer low flows associated with forest harvest for the small watersheds. Using recession curve analysis, the estimated range of the increase for average August streamflow for the four small watersheds in the Hinkle Creek Paired Watershed Study was 1.7 mm to 4.4 mm the first summer following forest harvest. August streamflow in the small watersheds was not distinguishable from preharvest levels within 5 years for all but one watershed, which had the highest proportion of watershed area harvested.
In recent years, interest has increased in silvicultural systems and harvest cuts that retain partial overstories, but there are few data available on the growth of the understory trees in such stands. We studied the response of overstory trees and underplanted seedlings, Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western redcedar (Thuja plicata), to a range of residual overstory densities. Forty to 70-year-old Douglas-fir stands in western Washington were harvested, leaving retention levels of 0, 8, 16, 24, 32, and 40% of full stocking. The 9-year response of the understory seedlings was species-dependent with Douglas-fir the largest in diameter (mean diameter 6.4 cm and mean height 3.8 m), western hemlock the tallest (mean diameter 5.5 cm and mean height 5.4 m), and redcedar the smallest (mean diameter 1.5 cm and mean height 1.5 m), in part because it was heavily browsed. Douglas-fir and western redcedar showed the greatest growth in the lowest retention levels (0 and 8%), and western hemlock responded best at the middle retention levels (8 and 16%).
One management technique that has been receiving attention for use against various forest insects are applications of bole-injected systemic insecticides. We evaluated the use of two such insecticides (emamectin benzoate applied at a rate of 0.07 ml Al/cm dbh and imidacloprid applied at a rate of 0.1 ml active ingredient (Al)/cm dbh) applied at two different times of the year (fall versus spring) for management of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough) (Lepidoptera: Lymantriidae) and the fir coneworm, Dyorictria abietivorella (Grote) (Lepidoptera: Pyralidae), insects that cause damage to Douglas-fir foliage and cones, respectively. Spring and fall bole injection of emamectin benzoate significantly reduced survival of Douglas-fir tussock moth caterpillars fed foliage from treated trees and reduced fir coneworm infestations on treated trees compared with untreated controls. Both fall and spring injection periods were equally effective. Douglas-fir tussock moth caterpillar survival was also significantly lowered when they fed on foliage from trees that had received spring injections of imidacloprid. At the dose tested, the fall treatment of imidacloprid did not reduce Douglas-fir tussock moth survival and neither fall or spring treatments significantly reduced infestation levels of fir coneworm. The results suggest that bole-injection treatments of emamectin benzoate can be effective in minimizing insect damage when applied the year prior to foliar feeding or harvest of the cone crop. Imidacloprid appears to be effective only for foliage protection and only when applied during the spring of the year that protection is needed.
The transition of modulus of elasticity (MOE) values from juvenile to mature wood marks the change between variable, low-quality wood to wood that is stronger and more consistent. Knowing the proportion of mature wood in a log can lower processing costs and allow for higher-quality products. We measured MOE in breast height pith-to-bark samples from lodgepole pine (Pinus contorta) trees in six sites in Alberta and British Columbia, Canada. We assessed eight different two-segment regression models (a first linear, quadratic, exponential or power segment, and a second linear or constant segment) to determine the transition point from juvenile to mature wood based on MOE. All eight models provided useful and significant estimates of the transition point. For the first segment (juvenile phase), the quadratic form predicted the latest transition to mature wood, the exponential form predicted the earliest transition, and the linear and power forms were intermediate. Use of a linear form for the second segment (mature phase) provided only a minor improvement over use of a constant. There were significant differences in transition point based on MOE among some of the sites, and correlations between transition points and tree diameter or height were found at two of the six sites.
We determined the difference in carbon (C) stocks and C emissions between treated and untreated ponderosa pine stands over 100 years on the Apache and Sitgreaves National Forests, Arizona, USA, under assumed treatment scenarios, wildfire frequency, and annual percentage of area burned. Compared with the no-action scenario, total C stocks (live and dead biomass) were lower in the treatment scenarios because of timber removals from thinnings, whereas aboveground live C stocks were higher in the treatment scenarios. When total C stocks were used as the baseline, net present values (NPVs) of treatments were in the range of -$759.42 and -$722.58 ha(-1) if timber and reduced requirement for C in a buffer pool were assumed to be creditable, and NPVs increased significantly if C in wood products was also eligible for C credit. When aboveground live C stocks were chosen as the baseline, NPVs ranged from -$759.42 to $2,700.44 ha(-1) with revenues from timber stumpage value, reduced buffer pool, and/or C in wood products. C emissions from simulated wildfires were lower in the two treatment scenarios than in the no-action scenario. The heavier thinning treatment resulted in lower C emissions from wildfires than with the lighter thinning treatment.
Many land managers in the Pacific Northwest have the goal of increasing late-successional forest structures. Despite the documented importance of Douglas-fir tree bark structure in forested ecosystems, little is known about factors influencing bark development and how foresters can manage development. This study investigated the relative importance of tree size, growth, environmental factors, and thinning on Douglas-fir bark furrow characteristics in the Oregon Coast Range. Bark furrow depth, area, and bark roughness were measured for Douglas-fir trees in young heavily thinned and unthinned sites and compared to older reference sites. We tested models for relationships between bark furrow response and thinning, tree diameter, diameter growth, and environmental factors. Separately, we compared bark responses measured on trees used by bark-foraging birds with trees with no observed usage. Tree diameter and diameter growth were the most important variables in predicting bark characteristics in young trees. Measured environmental variables were not strongly related to bark characteristics. Bark furrow characteristics in old trees were influenced by tree diameter and surrounding tree densities. Young trees used by bark foragers did not have different bark characteristics than unused trees. Efforts to enhance Douglas-fir bark characteristics should emphasize retention of larger diameter trees' growth enhancement.
Pricing strategies for forest biomass for power generation vary throughout North America, and are still evolving in the Pacific Northwest. The energy value of forest residues depends heavily on moisture content as does the cost of transportation. Payment for forest biomass that recognizes energy value poses challenges for buyers and suppliers. Maximizing the energy value per load increases the competitiveness of forest biomass suppliers.
Uneven-aged silviculture is increasingly favored where diverse management objectives require complex stand structures. Traditional uneven-aged silvicultural methods have been criticized as inflexible and lacking ecological basis. Stocking indices such as Reineke's stand density index (SDI) are flexible and easy to apply, but are not necessarily ecologically meaningful. We used data from Black Hills ponderosa pine stands to test whether SDI is a suitable proxy for leaf area index (LAI) in uneven-aged stands. LAI has clear ecological meaning, and is interpretable in terms of resource use efficiency and site quality. We found SDI explained almost 90% of the variation in LAI in 21 uneven-aged stands, and was unbiased by tree size. Our results show SDI is a useful tool for regulation of complex stand structures.
Stream temperatures were monitored on seven low-elevation western Oregon streams immediately after clearcut harvesting and 14-17 years later in two studies that examined buffer designs. One study on four streams used no-tree buffers with all trees next to the stream harvested within the clearcut units. The second study on three streams examined partial buffers designed to shade the stream only from direct sun. Streams with no-tree buffers in clearcuts 90 or 180 m long mostly exhibited significantly less warming 16-17 years after harvest than 1-5 years after harvest. Streams with partial buffers had originally shown slight response to harvest, and 14-15 years after harvest temperature trends were not different from preharvest trends. Percent cover and estimated radiation 14-17 years after harvesting were mostly similar in harvested and uncut areas. The exceptions were areas close to the streams that were cleared by beavers (Castor canadensis), where streams were wide resulting in canopy openings, and where gravel bars with minimal plant development occurred. Planted conifers in no-tree riparian areas provided less shade than hardwoods and were mostly suppressed by hardwoods or damaged by beavers.
On Nov. 30 to Dec. 1, 2011, an extreme wind event affected the central Sierra Nevada mountain region of California, causing extensive windthrow of trees. The wind event was caused by an extreme pressure gradient from north to south over Nevada and the Sierra that was unusual for the region in its duration, atypical wind direction, and high-intensity wind. Within Devils Postpile National Monument, there were approximately 118.5 windthrown trees km(-1). The average diameter at 1.37 m of windthrown trees was 55.36 cm, 2.2 times greater than that for pre-windstorm standing trees. Trees differed in damage type; 86% of trees were uprooted, whereas 14% were snapped, and dead trees were more likely to snap than uproot relative to live trees. Tree species was not a factor in likelihood of windthrow because species composition and relative abundance of windthrown trees were representative of the preexisting forest composition. This wind event is the most extensive on record for California's Sierra Nevada range and may have long-lasting effects on forest composition and function.
White spruce (Picea glauca [Moench] Voss) is a valuable commercial species found in interior and southcentral Alaska. Numerous regional and local volume tables or equations exist; however, no statewide model exists or has been tested for accuracy. There is a demand for an accurate model to determine the cubic-foot volume of white spruce trees in Alaska. Multiple models were developed for white spruce to estimate total and merchantable cubic-foot volume to a 2-, 4-, and 6-in. top. These multiple-entry (diameter and height) models were developed for both inside and outside bark volume from a 6-in. stump. The models were tested on a regional basis at various geographic locations and were shown to be highly accurate. The Alaska models chosen have R-2 at or near 0.99 and mean square error from 0 to 0.16 for all models. These models are shown to be superior to other white spruce models in Alaska.
Several methods are commonly used to determine the age of seedlings, and destructive aging methods are often assumed to be the most reliable. Terminal bud-scar counts can be used as a nondestructive alternative for aging seedlings, although clear criteria for which this method is appropriate are not well-known. This article evaluates the use of terminal bud-scar counts for aging seedlings of four conifer species in Glacier National Park, Montana. The results of our study suggest that terminal bud scars are reliable indicators of annual vertical growth, but that the accuracy of the method is limited to varying degrees by the age and height of seedlings. Method accuracy and error are more strongly related to seedling age and height for fast-growing species (western larch and lodgepole pine) than for slower-growing species (Engelmann spruce and Douglas-fir).
vary distinctly between species and growth parameters, providing specific insights for predictions of competitive effects and corresponding management implications. We, therefore, focus on measuring the nature of the development of the density-growth relationships over time, an approach possible in this case because of the frequency and precision of measurements at regular intervals during stand development. Methods Study Site Blodgett Forest Research Station (BFRS) is located on the western slope of the Sierra Nevada mountain range in California (38°52 N; 120°40 W). The study is within BFRS at an elevation of 1,320 m. The climate is Mediterranean with dry, warm summers (14–17° C) and mild winters (0–9° C). Annual precipitation averages 166 cm, most of it coming from rainfall during fall and spring months, while snowfall ( 35% of total precipitation) typically occurs between December and March. Before fire suppression (ca. 1890), the median point fire interval in the area was 9–15 years (Stephens and Collins 2004). The soil developed from andesitic lahar parent material. Soils are productive, with heights of mature codominant trees at BFRS typically reaching 31 m in 50 years. Vegetation at BFRS is dominated by a mixed conifer forest type, composed of variable proportions of five coniferous and one hardwood tree species (Tappeiner 1980). Giant sequoia is not among the five native conifer species present. BFRS is, however, approximately 16 km south of the northernmost native grove. The topography, soils, and climate of the study area are similar to the conditions found in native groves, although total precipitation at BFRS tends to be greater than in the southern Sierra Nevada where the majority of native groves occur. As within native groves, giant sequoia grows well in the study area, outgrowing all associated species through at least year 7 in planted canopy openings (Peracca and O’Hara 2008, York et al. 2004, 2011). In plantation settings throughout the Sierra Nevada, giant sequoias outgrow other conifer species through 3 decades after planting where soil productivity is high (Kitzmiller and Lunak 2012). Where it has been planted in Europe, it also typically outgrows other conifers (Knigge 1992). Study Design and Analysis for Height and Stem Diameter Seedlings were planted in 1989 at nine levels of density ranging from 2.1to 6.1-m hexagonal spacing between seedlings. To ensure that a tree was growing at each planting location, seedlings were initially double-planted, with the less vigorous seedling of the pair removed after 2 years. Treatments were applied across 0.08to 0.2-ha plots, depending on planting density (i.e., wider spacings required larger plots). Competing vegetation was removed periodically to control for any variation in resource availability not due to gradients in giant sequoia density (e.g., West and Osler 1995). Treatments were installed with a randomized block design (Figure 1), with each treatment randomly assigned once within three adjacent blocks (i.e., n 3 plot replications for each level of density). Measurements of height and dbh (1.37 m) for all trees following the 4th, 10th, 16th, and 22nd growing seasons are reported. For analysis, trees along the edges of the treated areas (i.e., “guard trees”) were removed to avoid interactions between treatments. Trees that had a dead or missing neighbor on any side after 22 years were also removed from the analysis (32 planting spots had dead or missing trees). The final dataset was made up of 2,303 trees. Results through the 7th year were presented by Heald and Barrett (1999). Here, detailed analysis of density effects is done for the most recent measurement (year 22), and all of the diameter and height measurements from 6-year intervals are used to reconstruct the trend in density-related competitive effects over time. Measurements are analyzed with the plot as the experimental unit and density as a continuous variable (n 3 replicates for each of 9 density levels 27 total sample units). The first step in the analysis of height and diameter growth was to fit the 22nd-year measurements with an appropriate equation that best described the relationship between density and tree size. We then used the selected 22nd-year equation to fit data from previous measurement years to reconstruct how the density effect developed. This approach has the drawback of assuming that the density-tree size relationship is similar over time because separate fits are not selected for each measurement period. It has the advantage, however, of providing the same slope parameter over time so that the trend of the density-size relationship can be quantified. Tracking the change in slope allowed us to profile the changing nature of competitive effects on the given growth parameter over time. For each level of planting density, the amount of horizontal growing space partitioned equally between each tree (m) was used as the predictor variable. Growing space was calculated by dividing the total space of each treatment area by the number of trees planted in the area with hexagonal spacing. The boundaries of the growing space for each treatment were defined to extend out beyond the stems of the perimeter trees, halfway to adjacent neighbor trees. Hence, growing space is here defined simply as the amount of horizontal space partitioned to each seedling at the time of planting and is related to linear distance between trees and inversely to tree density. From this point on, we use the term growing space to indicate stem density, but note that growing space is inversely related to density. The treatment gradient ranged from a minimum growing space of 3.7 m/stem (2,702 stems/ha) to a maximum of 28.4 m/stem (353 stems/ha). We used the 22nd-year measurements to select the best model from a set of bona fide candidate models (sensu Johnson and Omland 2004) to describe the effect of growing space on average individual tree growth in terms of height and stem diameter. We then used the selected model to fit measurements from previous years, comparing the models’ slope parameters and corresponding 95%-confidence intervals between years to track the change in competitive effects over time. Candidate models had to be simple (i.e., Figure 1. Overhead view of randomized block design from the giant sequoia density study at Blodgett Forest, CA. WEST. J. APPL. FOR. 28(1) 2013 31 few parameters) quantifications of plausible growing space-size relationships that each represented separate biological mechanisms at work. The candidate set included four relationships. The first was a simple linear equation, reflecting an additive relationship between growing space and tree size (i.e., more space equals more growth without any diminishing or increasing returns): Tree size a b*growing space where a is the y-intercept and b is linear coefficient (i.e., the slope). The management application of such a relationship is that individual tree growth is maximized at the widest spacing. The second model was a log-linear fit, reflecting a multiplicative effect of growing space on tree size: Tree size a b(log*growing space) A log-linear fit occurs when tree size increases monotonically across the range of growing space considered. Growth is maximized at the widest spacing, but unlike with a linear fit, the returns in terms of tree size diminish with the widest spacings. The third model was a quadratic fit, reflecting an eventual negative effect of growing space on tree size: Tree size a b*growing space c*growing space where c is the quadratic coefficient. A quadratic fit occurs when there is an eventual negative effect of increased growing space on tree size. This has been known to occur when, for example, trees grow taller as a response to near-neighbor shading (Gilbert et al. 2001). The final model was a Michaelis–Menten fit, which is an asymptotic curve reflecting a saturating effect: Tree size d*growing space / e growing space where d is the asymptote of the curve (the maximum tree size predicted) and e is the growing space at which tree size is half of maximum. This relationship implies a maximum growing space where further increases cause neither greater nor less in terms of tree size. It is worth noting that these mathematical relationships, when expressed in graphical form and when used for making inferences to management, are constricted by the limits of the data. For example, if a quadratic form were to be chosen, we obviously do not expect tree size to trend to zero. Nor would we expect a linear relationship to continue indefinitely. While differences between these curves can be subtle when correlations are variable, the high precision of this particular data set allowed us to distinguish between them. Akaike’s information criteria weights (AICw), with a small sample correction (Sugiura 1978), were used to rank and choose the best models. AIC weights are likelihood transformations of raw AIC values, and are, therefore, more meaningful than raw values when comparing how well each model performed. An AICw of 0.80, for example, implies an 80% likelihood of that model being the best model when compared with the other candidate models and given the data (Burnham and Anderson 2002). While raw AIC values are typically interpreted as the lowest value being the best model, AIC weights are the opposite. We also report the evidence ratio, which is the ratio between the best model’s AICw and each other model. The evidence ratio essentially measures how much better the best model was. Measurements and Analysis for Branch Diameter, Branch Density, and Stem Volume Branch diameter and branch density data were collected following the 16th year only (timed to coincide with a logical age for conducting artificial pruning). The branch closest to 1.37-m stem height on the west side of each tree was measured with digital calipers where the branch attached to the stem (while avoiding the swollen branch collar). To measure br
