Fact Sheet: Unsupported inferences of high-severity fire in historical dry forests of the western United States: response to Williams and Baker.

A recent study in Global Ecology and Biogeography (Williams and Baker 2012, hereafter W&B) described the historical conditions of forest structure and fire regimes on four large landscapes in Arizona, Colorado and Oregon. W&B used notes made by land surveyors who worked in these landscapes in the late 1800s and early 1900s, a period before many impacts of modern land uses, such as large-scale fire control, took place. Based on these data, W&B developed an interpretation of past conditions in ponderosa pine and dry mixed conifer forests that differs from previous research. W&B asserted that these forests historically included relatively high densities because of past fire regimes of moderate to high severity fires. Natural regeneration following such fires would lead to numerous, small and similar aged trees. W&B concluded that current management practices of thinning small trees and using low-severity prescribed burns would damage forests, rather than restore them. The inferences drawn by W&B about past forest ecology contrast sharply those reported by numerous previous researchers, who used tree-ring and historical data to show that dry forests had predominantly surface fire regimes with relatively open, uneven-aged forests. A group of 18 forest ecologists, concerned about the lack of scientific support for the conclusions by W&B, wrote a response (Fule et al. 2013). This fact sheet summarizes the key issues of our response. A rebuttal to the response was published by Williams and Baker (2014)

SemGrAM - Integrating semantic graphs into association rule mining

To date, most association rule mining algorithms have assumed that the domains of items are either discrete or, in a limited number of cases, hierarchical, categorical or linear. This constrains the search for interesting rules to those that satisfy the specified quality metrics as independent values or as higher level concepts of those values. However, in many cases the determination of a single hierarchy is not practicable and, for many datasets, an item’s value may be taken from a domain that is more conveniently structured as a graph with weights indicating semantic (or conceptual) distance. Research in the development of algorithms that generate disjunctive association rules has allowed the production of rules such as Radios V TVs -> Cables. In many cases there is little semantic relationship between the disjunctive terms and arguably less readable rules such as Radios V Tuesday -> Cables can result. This paper describes two association rule mining algorithms, SemGrAMG and SemGrAMP, that accommodate conceptual distance information contained in a semantic graph. The SemGrAM algorithms permit the discovery of rules that include an association between sets of cognate groups of item values. The paper discusses the algorithms, the design decisions made during their development and some experimental results.Sydney, NS

Species and canopy cover map development using Landsat Enhanced Thematic Mapper imagery for Grand Canyon National Park

Overstory vegetation maps of species and canopy cover were developed from Landsat 7 Thematic Enhanced Thematic Mapper satellite imagery. Ecosystem Monitoring plot data, collected during the 1997-2001 field seasons, were used as training sites for the image classification. Sixty-two species classes and four canopy cover classes were mapped. The maps will be used to support a Joint Fire Science Program funded project to model long-term fire regimes and ecological change using fire history, climate, and forest structure data. The calibrated model will then be used to assess fire behavior under current fuel conditions and to evaluate and compare future fuel treatments that may include prescribed burning and thinning

Technical reference: Seventh biennial conference of research on the Colorado Plateau

Seventh Biennial Conference of Research on the Colorado Platea

Experiences in building a tool for navigating association rule result sets

Practical knowledge discovery is an iterative process. First, the experiences gained from one mining run are used to inform the parameter setting and the dataset and attribute selection for subsequent runs. Second, additional data, either incremental additions to existing datasets or the inclusion of additional attributes means that the mining process is reinvoked, perhaps numerous times. Reducing the number of iterations, improving the accuracy of parameter setting and making the results of the mining run more clearly understandable can thus significantly speed up the discovery process. In this paper we discuss our experiences in this area and present a system that helps the user to navigate through association rule result sets in a way that makes it easier to find useful results from a large result set. We present several techniques that experience has shown us to be useful. The prototype system – IRSetNav – is discussed, which has capabilities in redundant rule reduction, subjective interestingness evaluation, item and itemset pruning, related information searching, text-based itemset and rule visualisation, hierarchy based searching and tracking changes between data sets using a knowledge base. Techniques also discussed in the paper, but not yet accommodated into IRSetNav, include input schema selection, longitudinal ruleset analysis and graphical visualisation techniques.Adelaide, S

Review Protocol – Final: Do thinning and/or burning treatments on ponderosa pine and related forests in western USA produce restoration of natural fire behaviour?

The aim of this review is to investigate whether thinning and/or burning treatments on ponderosa pine and related forests in western USA produce restoration of natural fire behaviour

Changes in gambel oak densities in southwestern ponderosa pine forests since Euro-American settlement

Densities of small-diameter ponderosa pine (Pinus ponderosa) trees have increased in southwestern ponderosa pine forests during a period of fire exclusion since Euro-American settlement in the late 1800s. However, less well known are potential changes in Gambel oak (Quercus gambelii) densities during this period in these forests. We reviewed published literature to summarize changes in oak density in ponderosa pine forests over the past 140 years and evaluated the possibility that large-diameter oaks have decreased in density. All nine studies examining oak density changes found that densities of small-diameter oaks have escalated. Increases ranged from 4- to more than 63-fold. These increases are comparable on many sites to those of ponderosa pine. Studies in northern Arizona, which analyzed cut stumps and past and present diameter distributions, did not find strong evidence that large-diameter oaks on average have declined in density. However, since oak cutting varied across the landscape, this important question needs additional study. Actively or passively managing Gambel oak requires decisions about desired future conditions and how to attain them. A possible contention for passive management—that the overall abundance of oak has decreased—is not supported by research published to date

Fire effects on gambel oak in southwestern ponderosa pine-oak forests

Gambel oak (Quercus gambelii) is ecologically and aesthetically valuable in southwestern ponderosa pine (Pinus ponderosa) forests. Fire effects on Gambel oak are important because fire may be used in pine-oak forests to manage oak directly or to accomplish other management objectives. We used published literature to: (1) ascertain historical fire regimes in pine-oak forests, (2) discern prescribed burning effects on Gambel oak survival and diameter growth, and (3) provide suggestions for using fire to manage oak. Frequent fire is part of Gambel oak’s historical environment, as historical fire return intervals often averaged less than 10 years in pine-oak forests. More than 66 percent of oaks greater than 6 inches (15 cm) in diameter were alive at least 5 years after two contemporary prescribed fires, whereas survival was low (percent) for small oaks less than 2 inches (5 cm) in diameter. Top-killed oaks resprout prolifically, suggesting that fire can maintain shrub-sprout forms of oak constituting browse and cover for some wildlife species. Unlike mechanically thinning competing trees, burning has not been found to increase oak diameter growth. We conclude that fire can be used to manage Gambel oak densities and growth forms, and that large oaks can be maintained during low-intensity burning. Several tactics may enhance survival of large oaks during prescribed fire: keeping pine slash away from oak boles, avoiding lighting near oaks or reducing fire intensity near oaks, and raking fuels away from oak boles

Survival and sprouting responses of Chihuahua Pine after Rodeo-Chediski fire on the Mogollon Rim, Arizona

Chihuahua pines (Pinus leiophylla Schiede and Deppe var. chihuahuana Engelmann) were surveyed on 11 study plots on the Mogollon Rim in east central Arizona to compare characteristics of trees that sprouted from the base or root collar after the Rodeo-Chediski fire with those of trees that did not sprout. The differences in trees killed and top-killed by the fire versus those that survived were also assessed. Trees that sprouted were significantly smaller in height and diameter at breast height; they also experienced lower fire intensities than trees that did not sprout. Smaller trees had higher incidences of mortality than larger trees. These results indicate that, even though Chihuahua pine has fire resiliency, sprouting rates after fire are related to size of trees, age of trees, and burn intensity. Since Chihuahua pine is a rare species in the area studied, its ability to recover from and tolerate fire could prove advantageous for sustainability

Fact sheet: Carbon costs of mitigating high-severity wildfires

The increasing frequency of large, severe wildfires in western United States forests presents a challenge in terms of maintaining forest health, especially in the face of climate change. In addition to losses of forest cover, species diversity and increased soil erosion, severe wildfires release carbon stored in forest trees and soils, and reduce the number of trees that can remove carbon from the atmosphere. Altering the forest structure by thinning smaller trees and reducing surface fuels through prescribed burning has proven effective in reducing fire severity. However, thinning and prescribed burning comes with its own costs because these activities remove trees and downed wood that store carbon