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ISSN: 0022-1201

Don C. Bragg

Current Issue

Volume 113, Number 1, January 2015
  • editor's note
  • brief communication
    geospatial technologies

    Urban Tree Height Assessment Using Pictometry Hyperspatial 4-Inch Multispectral Imagery


    Tree height is a critical variable of forest inventory assessments, and estimating the height of trees has been a component of forest inventory assessments for decades. The actual tree height of 60 open-grown baldcypress (Taxodium distichum) trees measured with a telescopic height pole were compared to Pictometry hyperspatial 4-in. multispectral imagery estimated tree height on the campus of Stephen F. Austin State University, Nacogdoches, Texas. Linear correlation coefficients (r) between actual tree height and Pictometry-estimated tree height for all 60 trees and the shortest 30 and tallest 30 trees were >0.997 for all r values. Pictometry-estimated tree height was within, on average, 1.77, 2.15, and 1.40% of actual tree height for all 60 trees, the shortest 30 trees, and the tallest 30 trees, respectively. All three paired t-tests, for all 60 trees, the shortest 30 trees, and the tallest 30 trees, resulted in a P value =0.08, indicating that there was no statistical significance between actual and estimated tree height at a 95% confidence level. Pictometry-estimated tree height can be used in lieu of field-based tree height estimation for open-grown urban forests.


    Estimating tree height accurately, which is a critical component of any forest inventory, can be time-consuming and expensive. Tree height estimated remotely using the Pictometry web-based interface with high spatial resolution digital imagery was shown to be highly accurate. Estimation of tree height by remotely sensed imagery can be used in lieu of field-based tree height estimation for open-grown forests.

  • research articles

    Assessing the Relationship between Different Forms of Landowner Assistance and Family Forest Owner Behaviors and Intentions


    In this study, we examine how family forest owners who receive various types of assistance differ from unassisted landowners with respect to their forestland management practices, attitudes and concerns, and future management, use, and ownership intentions. We do so by utilizing a national database containing information on private forest owners and the forestland they own. By defining an assisted landowner according to several attributes contained in this database (e.g., has a forest management plan, received cost-share assistance, or received advice), important similarities and differences between recipients and nonrecipients of various types of assistance are identified. The study shows that assisted and unassisted landowners are different with respect to several characteristics of the owners and the forestland they own, land management practices undertaken, and reasons for forest landownership. For example, assisted landowners are more likely to harvest timber and improve wildlife habitat than the unassisted owners. Yet no distinctions are found between assisted and unassisted landowners with respect to their plans to either subdivide or sell their land. In many cases, the differences between assisted and unassisted landowners are not related to the type of assistance the landowner received.


    This study found that forest landowners are more likely to undertake certain land management activities if they have received assistance. Therefore, linking forest landowners to some form of assistance may be important if a goal is to have landowners adopt practices such as wildlife habitat improvement or tree planting. Yet our analysis suggests that landowners are not very sensitive to the kind of assistance they receive. Landowners who received one of three forms of assistance (management plan, financial assistance, or advice) are similarly distinct from landowners who have not received the assistance. Our analysis also found little difference between assisted and unassisted owners when it comes to their plans to subdivide or sell their forestland. How policymakers should respond to these findings depends on the public policy goals. If the goal is to encourage landowners to implement land management practices such as improving wildlife habitat or reforestation, then providing some type of interaction with and assistance to landowners is important. Because the specific type of assistance does not appear to be an important factor, one strategy is to focus assistance efforts to reach the largest private forest acres per dollar spent. However, if the public policy goal is to "keep forest as forest," policymakers, mangers, and extension foresters may need to diversify or expand current assistance approaches.

    harvesting & utilization

    Landscape and Individual Tree Predictors of Dark Heart Size in Sugar Maple


    The high value of sugar maple logs and lumber depends on the wood being light-colored and clear of defects. Predicting the size of dark hearts in trees before they are harvested is very important to foresters, forest landowners, and sawmills. We investigated many possible predictors of the heart size of sugar maple in 10 sites in New York State. Heart size ratios by site ranged from 12 to 42%, averaging 23%. At the site level, trees with large hearts were more common on more acid soils (P = 0.04). Flaky bark, poor crown ratios, and lower grade stems were correlated with large hearts across the sample of 265 trees. Visible tree injury, competition, and tree diameter were not consistently related to heart size ratios of trees. Steep slopes were associated with large hearts. Other physiographic factors (slope and landform) differed in their effect by site, possibly due to local histories of storm damage. In conclusion, predicting dark heart in sugar maple is likely to remain challenging.


    Sugar maple is one of the most important commercial hardwood species in the United States and Canada. Its wood is highly valued because of the light color and even grain. A large dark heart greatly reduces the value of sugar maple logs and lumber. Unfortunately, it is difficult to predict the sizes of dark hearts in standing sugar maple. Our study found different factors to indicate dark heart size at different sites, but, overall, sites with less acid soils had fewer large hearts. We found no evidence that the proportion of dark heart increases with tree diameter. Consequently, forest managers should use well established silvicultural practices to minimize dark heart in forest stands, including crop tree selection based on grade, bark type, and crown ratio, all of which are good predictors of dark heart. These crop trees can be tended over several decades until economic maturity. Foresters attempting to place a value on sugar maple stumpage could take advantage of soil tests or soil maps, in addition to individual tree predictors, to minimize the value reduction resulting from dark heart.

    forest ecology

    Forest Site Classification for Cultural Plant Harvest by Tribal Weavers Can Inform Management


    Do qualitative classifications of ecological conditions for harvesting culturally important forest plants correspond to quantitative differences among sites? To address this question, we blended scientific methods (SEK) and traditional ecological knowledge (TEK) to identify conditions on sites considered good, marginal, or poor for harvesting the leaves of a plant (beargrass; Xerophyllum tenax) used in tribal basket weaving. We relied on voluntary participation of six expert weavers, a stratified, randomized field sample, discriminant analysis (DA), a standardized color system, and paired t-tests. We accepted each weaver's classification (good, marginal, or poor) of forested sites for beargrass harvest and then measured forest and plant attributes on two plots at each harvest area in each class (n = 72). The DA yielded descriptive but not predictive results. Coarse woody debris (CWD) levels and the number of trees (trees per acre [TPA]) differed significantly between good and poor sites across California, Oregon, and Washington, whereas basal area did not. Good sites had less CWD (P = 0.0360) and fewer TPA (P = 0.001) than poor sites. Variations in leaf color decreased as the site class for plant harvest improved. Results reveal a crosswalk between ecological knowledge derived via SEK and TEK for culturally important plants.


    Different types of ecological knowledge can contribute to identifying forest management objectives for culturally important plants. Study results imply that managing tree density can provide understory conditions to promote the growth of beargrass leaves preferred by tribal weavers. Results also imply that managing down wood levels is important so that coarse woody debris (CWD) (>3 in.) is not a physical barrier for tribal harvesters. Across sites in California, Oregon, and Washington, average tree BA per acre did not differ significantly, ranging between 175 and 197 ft2/acre. On sites considered good for beargrass harvest, however, the BA was distributed on fewer trees (average 127) than it was on sites the tribal weavers identified as marginal (average 177) or poor for harvest (average 172). A similar trend existed for deadwood. Namely, the average amount of total surface wood and litter increased as the site classification declined in quality, with good = 14 tons/acre, marginal = 19 tons/acre, and poor = 22 tons/acre. Taken together, the forest conditions identified by tribal weavers as good for harvesting beargrass had, on average, significantly fewer, larger diameter trees and less surface wood, litter, and CWD than did poor sites. The structural elements preferred by tribal weavers for beargrass harvest, therefore, relate directly to those associated with managing fire behavior in similar forest types.

    fire & fuels management

    Constraints on Mechanized Treatment Significantly Limit Mechanical Fuels Reduction Extent in the Sierra Nevada


    Wildland firefighting is an inherently dangerous activity, and aviation-related accidents in particular comprise a large share of firefighter fatalities. Due to limited understanding of operational factors that lead to aviation accidents, it is unclear how local decisionmakers, responsible for requesting aviation support, can mitigate the risk of an aviation accident once resources are requested. This research expands the knowledge base regarding the quantification and analysis of aerial firefighting exposure by developing methods to evaluate expected aviation accident rates at the incident level using a metric called the aviation exposure index (AEI). Our analysis is based on coupling historical aviation accident rates (10-year average) with observed aviation resource use. As an example of the applicability of the approach, we present results according to aircraft type, unique incident, and incident jurisdiction for large wildfires that occurred during the 2012 US fire season. Ideally, the AEI could be automatically calculated and incorporated into incident decision support systems to help guide fire managers as they balance the complicated tradeoffs between attaining wildfire management objectives and reducing the exposure of individuals engaged in aerial firefighting activities.


    In this study, we evaluate methods to estimate the expected accident rates of aviation resources on individual large wildland fires with the introduction of the aviation exposure index (AEI), using the 2012 US fire season as a test case. We propose that efforts aimed at tracking expected aviation accidents on wildland fires are consistent with recent direction from the chief of the USDA Forest Service, stating that all suppression actions should be evaluated by balancing the likelihood of suppression success and avoided natural and developed resource loss achieved by suppression activities, against the type and amount of firefighter exposure to hazards. The real-time calculation of the AEI could help individuals charged with managing large wildfires consider the level of exposure of aviation personnel to the hazards of the wildland fire environment. The approach developed here could also help managers to better consider potential risk transference between aviation and ground personnel, for instance in situations where rugged and inaccessible terrain would lead fire managers to rely more heavily on aviation resources because they deem the risk to ground personnel to be too high.

    fire & fuels management

    Forest Fire Severity Patterns of Resource Objective Wildfires in the Southern Sierra Nevada


    Distinguishing favorable versus undesirable outcomes of wildland fires in coniferous forest ecosystems is challenging and requires a clear and objective approach. I applied the natural range of variation (NRV) concept and used fire severity indicators to evaluate the possible effects of wildfires managed for resource benefits (hereafter "resource objective wildfires") in four national forests of the southern Sierra Nevada, California. Results indicated that resource objective wildfires in coniferous forests were overwhelmingly within the NRV with respect to fire severity proportions and mean and maximum high-severity patch size. These results suggest that the continued and expanded use of resource objective wildfires, including the establishment of "demonstration firesheds" within and across administrative boundaries, has the potential to vastly increase the scale of regional forest restoration efforts in the western United States.


    Unplanned ignitions burning in favorable weather conditions and terrain offer unique opportunities to restore and maintain the resilience of forest ecosystems. These wildfires managed for resource objectives are ideally suited to large wilderness or inventoried roadless areas but may also include self-contained "firesheds" outside the wildland urban interface. In the national forests of the southern Sierra Nevada, 17 wildfires between 1,000 and 20,000 acres in size have been successfully managed for natural resource objectives, despite decades of fire exclusion in these topographically complex, fire-adapted forest landscapes. Fire severity patterns within these areas were overwhelmingly within the natural range of variation, and in many cases greater fire severity effects (e.g., greater proportions of moderate severity fire) could be desirable to advance structural restoration and other objectives. Collaborative efforts, "all lands" partnerships, and the use of demonstration landscapes or "firesheds" can assist managers in achieving forest restoration across large and complex landscapes.

  • review article
    harvesting & utilization

    The Burning Question: Does Forest Bioenergy Reduce Carbon Emissions? A Review of Common Misconceptions about Forest Carbon Accounting


    Critical errors exist in some methodologies applied to evaluate the effects of using forest biomass for bioenergy on atmospheric greenhouse gas emissions. The most common error is failing to consider the fate of forest carbon stocks in the absence of demand for bioenergy. Without this demand, forests will either continue to grow or will be harvested for other wood products. Our goal is to illustrate why correct accounting requires that the difference in stored forest carbon between harvest and no-harvest scenarios be accounted for when forest biomass is used for bioenergy. Among the flawed methodologies evaluated in this review, we address the rationale for accounting for the fate of forest carbon in the absence of demand for bioenergy for forests harvested on a sustained yield basis. We also discuss why the same accounting principles apply to individual stands and forest landscapes.


    A growing market for energy produced from forest biomass has arisen because of the potential to mitigate climate change by replacing fossil fuel energy. However, managers who want to access this market should be aware that the benefits of forest bioenergy depend on evaluation of forest management options against a baseline scenario considering what happens to carbon stocks if biomass is not harvested for energy. Among the more favorable options are the use of residue from ongoing harvest operations for traditional wood products (lumber and pulp) and application of intensive silviculture to regeneration of harvested stands. Establishment of new bioenergy-designated plantations on abandoned/degraded lands requires more time for forest biomass to become available for harvest but has the advantage of a low carbon stock value baseline. The least favorable options include harvest of standing live trees, both in addition to and in lieu of ongoing harvest operations for traditional wood products. Policies for bioenergy use also need to recognize that accounting for emission benefits when fossil fuels are replaced requires accounting for forest carbon (either in forest or in traditional wood products) that would have continued to exist if fossil fuels were not replaced by bioenergy.

  • commentary
  • 2014 proceedings

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