USDA Forest Service / UNL Faculty Publications

Genetic Errors Associated with Population Estimation Using Non-Invasive Molecular Tagging: Problems and New Solutions

Kevin S. McKelvey et al. — Wed, 27 Feb 2013 11:39:57 PST

The use of non-invasive DNA-based sampling is becoming increasingly popular. However, the misidentification of individuals due to genotyping error (primarily allelic dropout) is a critical problem, especially when using individuals in the capture–mark–recapture (CMR) approach to estimate population size. We propose 2 simple and cost-effective tests, Examining Bimodality (EB) and Difference in Capture History (DCH), to determine whether a sample contains genotyping errors and the relative magnitude of the problem. These tests formalize currently used approaches for identifying genotyping errors. We evaluate the efficacy of these tests using simulated CMR data. Results show that both tests are effective at detecting genotyping errors and provide a strong indication of whether the data are error free. The EB and DCH tests apply to data in which multiple samples are associated with individuals, such as those generated by CMR sampling. Managers need to be able to identify and eliminate genotyping errors to produce population estimates that are both unbiased and scientifically defensible.

Geology of the Early Arikareean Sharps Formation on the Pine Ridge Indian Reservation and Surrounding Areas of South Dakota and Nebraska

Thomas H. McConnell et al. — Wed, 27 Feb 2013 11:35:57 PST

Based on geologic mapping, measured sections, and lithologic correlations, the local features of the upper and lower type areas of the Early Arikareean (30.8–20.6 million years ago) Sharps Formation are revised and correlated. The Sharps Formation above the basal Rockyford Member is divided into two members of distinct lithotypes. The upper 233 feet of massive siltstones and sandy siltstones is named the Gooseneck Road Member. The middle member, 161 feet of eolian volcaniclastic siltstones with fluvially reworked volcaniclastic lenses and sandy siltstone sheets, is named the Wolff Camp Member. An ashey zone at the base of the Sharps Formation is described and defined as the Rockyford Ash Zone (RAZ) in the same stratigraphic position as the Nonpareil Ash Zone (NPAZ) in Nebraska. Widespread marker beds of fresh water limestones at 130 feet above the base of the Sharps Formation and a widespread reddish-brown clayey siltstone at 165 feet above the base of the Sharps Formation are described. The Brown Siltstone Beds of Nebraska are shown to be a southern correlative of the Wolff Camp Member and the Rockyford Member of the Sharps Formation. Early attempts to correlate strata in the Great Plains were slow in developing. Recognition of the implications of the paleomagnetic and lithologic correlations of this paper will provide an added datum assisting researchers in future biostratigraphic studies. Based on similar lithologies, the Sharps Formation, currently assigned to the Arikaree Group, should be reassigned to the White River Group.

Midday stomatal conductance is more related to stem rather than leaf water status in subtropical deciduous and evergreen broadleaf trees

Yong-Jiang Zhang et al. — Mon, 17 Dec 2012 08:16:58 PST

Midday depressions in stomatal conductance (g_s) and photosynthesis are common in plants. The aim of this study was to understand the hydraulic determinants of midday g_s, the coordination between leaf and stem hydraulics and whether regulation of midday g_s differed between deciduous and evergreen broadleaf tree species in a subtropical cloud forest of Southwest (SW) China. We investigated leaf and stem hydraulics, midday leaf and stem water potentials, as well as midday g_s of co-occurring deciduous and evergreen tree species. Midday g_s was correlated positively with midday stem water potential across both groups of species, but not with midday leaf water potential. Species with higher stem hydraulic conductivity and greater daily reliance on stem hydraulic capacitance were able to maintain higher stem water potential and higher g_s at midday. Deciduous species exhibited significantly higher stem hydraulic conductivity, greater reliance on stem capacitance, higher stem water potential and g_s at midday than evergreen species. Our results suggest that midday g_s is more associated with midday stem than with leaf water status, and that the functional significance of stomatal regulation in these broadleaf tree species is probably for preventing stem xylem dysfunction.

The relationship between male moth density and female mating success in invading populations of Lymantria dispar

Patrick C. Tobin et al. — Mon, 17 Dec 2012 08:10:28 PST

The successful establishment of non-native species in new areas can be affected by many factors including the initial size of the founder population. Populations comprised of fewer individuals tend to be subject to stochastic forces and Allee effects (positive-density dependence), which can challenge the ability of small founder populations to establish in a new area. Although the conceptual relationship between initial colony size and establishment success has been previously documented, it is not trivial to estimate precisely the colony size needed to ensure colony persistence. Over the last 40 years, there have been many studies on the probability of mating success of female Lymantria dispar (L.) (Lepidoptera: Lymantriidae) in the USA related to background male moth densities. We were motivated by this wealth of data and sought to combine the results from these prior studies with the goal of estimating a robust measure of the male moth density required to achieve varying levels of female mating success. Although the data are specific to L. dispar, the pheromone communication system in L. dispar is not unique and thus the results of this analysis could be broadly applicable to our general understanding of Lepidoptera mating behavior.

Interactive influences of ozone and climate on streamflow of forested watersheds

Ge Sun et al. — Mon, 17 Dec 2012 08:06:15 PST

The capacity of forests to mitigate global climate change can be negatively influenced by tropospheric ozone that impairs both photosynthesis and stomatal control of plant transpiration, thus affecting ecosystem productivity and watershed hydrology. We have evaluated individual and interactive effects of ozone and climate on late season streamflow for six forested watersheds (38–970 000 ha) located in the Southeastern United States. Models were based on 18–26 year data records for each watershed and involved multivariate analysis of interannual variability of late season streamflow in response to physical and chemical climate during the growing season. In all cases, some combination of ozone variables significantly improved model performance over climate-only models. Effects of ozone and ozone × climate interactions were also consistently negative and were proportional to variations in actual ozone exposures, both spatially across the region and over time. Conservative estimates of the influence of ozone on the variability (R²) of observed flow ranged from 7% in the area of lowest ozone exposure in West Virginia to 23%in the areas of highest exposure in Tennessee. Our results are supported by a controlled field study using free-air concentration enrichment methodology which indicated progressive ozone-induced loss of stomatal control over tree transpiration during the summer in mixed aspen-birch stands. Despite the frequent assumption that ozone reduces tree water loss, our findings support increasing evidence that ozone at near ambient concentrations can reduce stomatal control of leaf transpiration, and increase water use. Increases in evapotranspiration and associated streamflow reductions in response to ambient ozone exposures are expected to episodically increase the frequency and severity of drought and affect flow-dependent aquatic biota in forested watersheds. Regional and global models of hydrologic cycles and related ecosystem functions should consider potential interactions of ozone with climate under both current and future warmer and ozone-enriched climatic conditions.

Stochastic and deterministic processes regulate spatio-temporal variation in seed bank diversity

Alejandro A. Royo et al. — Mon, 17 Dec 2012 07:53:21 PST

Question: Seed banks often serve as reservoirs of taxonomic and genetic diversity that buffer plant populations and influence post-disturbance vegetation trajectories; yet evaluating their importance requires understanding how their composition varies within and across spatial and temporal scales (α- and β-diversity). Shifts in seed bank diversity are strongly governed by the deterministic role of differential seed longevities. Nevertheless, spatio-temporal variability in propagule depletion from and recruitment into seed banks may alter both α- and β-diversity. Here, we ask to what degree deterministic seed exhaustion, stochasticity in recruitment and mortality, or both, shape α- and β-diversity?

Location: Temperate hardwood forest stands of varying ages in northern Pennsylvania, USA.

Methods: We surveyed the seed bank and herbaceous vegetation communities at 39 sites and examined whether the species richness, abundance and composition of either community differs among and within sites of increasing age ranging from 43 to 106 yr old. We explored how α-diversity (species richness) and abundance (percentage cover, seed density) varied across the chronosequence age using regression analyses. We analyzed differences in β -diversity (community composition) using permutational multivariate analyses (i.e. PERMANOVA, PERMDISP). Finally, we tested whether community composition of the herbaceous layer and seed bank communities exhibited nestedness, where nestedness refers to the degree to which less species-rich sites are a non-random subset of more species-rich sites.

Results: We found seed bank α-diversity and abundance consistently declined across a gradient of increasingly older sites. Moreover, nestedness analyses indicated species composition at older sites represented a subset of the species found at younger sites characterized by species with persistent seeds. Nevertheless, seed bank communities demonstrated divergent compositional trajectories, whereby older sites were increasingly dissimilar, not only from younger sites, but also from each other.

Conclusions: Our results suggest that even in assemblages strongly structured by deterministic forces, such as seed banks, minor stochastic differences in colonization and extinction events may increase β-diversity over time. Therefore, we argue deterministic and stochastic processes are complementary factors governing post-disturbance turnover in species assemblages, and suggest that seed banks contribute to species’ persistence and overall forest community diversity across space and time.

Seasonal dynamics and age of stemwood nonstructural carbohydrates in temperate forest trees

Andrew D. Richardson et al. — Mon, 17 Dec 2012 07:43:46 PST

Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress.
We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars in a subset of trees using the radiocarbon (¹⁴C) bomb spike. With these data, we then tested different carbon (C) allocation schemes in a process-based model of forest C cycling.
We found that the nonstructural carbohydrates are both highly dynamic and about a decade old. Seasonal dynamics in starch (two to four times higher in the growing season, lower in the dormant season) mirrored those of sugars. Radiocarbon-based estimates indicated that the mean age of the starch and sugars in red maple (Acer rubrum) was 7–14 yr.
A two-pool (fast and slow cycling reserves) model structure gave reasonable estimates of the size and mean residence time of the total NSC pool, and greatly improved model predictions of interannual variability in woody biomass increment, compared with zero- or one-pool structures used in the majority of existing models. This highlights the importance of nonstructural carbohydrates in the context of forest ecosystem carbon cycling.

Modelling approaches for relating effects of change in river flow to populations of Atlantic salmon and brown trout

J. D. Armstrong et al. — Mon, 17 Dec 2012 07:32:50 PST

Modelling approaches for relating discharge to the biology of Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., growing in rivers are reviewed. Process-based and empirical models are set within a common framework of input of water flow and output of characteristics of fish, such as growth and survival, which relate directly to population dynamics. A continuum is envisaged incorporating various contributions of process and empirical structure as practical and appropriate to specific goals. This framework is compared with, and shown to differ from, approaches whose output is in the form of quantity and form of habitat (or usable area) based on its frequency of use by fish, which then is assumed to have some relationship with fish performance. A simple conceptual modeling approach is also developed to relate water flow to fish population characteristics to assess the likelihood of simple relationships between flow and usable area thresholds. Basic predictions of the model are tested against empirical data from a long-term individual-based study of juvenile S. salar and resident brook trout, Salvelinus fontinalis (Mitchell), in West Brook, Massachusetts. For this system, growth rates of both species increased linearly with flow during spring, summer and autumn months and bore no relation to Q₉₅ or wetted-width discontinuities. Winter is identified as a season during which water might be abstracted most safely, but cautiously given sparse knowledge of wild salmonid fish at this time of year. These results, together with the fundamental conceptual problems inherent in usable area-based approaches, suggest that models that relate directly to fish performance outcomes may be more robust as a basis for flow prescriptions. However, this utility will depend strongly on our ability to generalize from a limited set of empirical studies and to use the results of these studies of management actions to inform and improve future models.

Towards a life-history-based management framework for the effects of flow on juvenile salmonids in streams and rivers

K. H. Nislow et al. — Mon, 17 Dec 2012 07:26:07 PST

Salmonid fishes have complex life cycles involving major changes in habitat requirements at different stages in their life history. Effects of changes in flow and flow regime on salmonids are therefore highly stage specific. Successful management requires consideration of stage-specific influences and integration of these effects over the entire life history to predict ultimate impacts on abundance and population viability. The state of science regarding stage-specific influences of flow regime on juvenile salmonids and their habitats, referring specifically to fundamental attributes of natural regimes and to characteristic alterations of these regimes associated with water management, is reviewed. It appears that a key consideration in integrating the stage-specific impacts of flow is the extent to which flow-related losses or gains early in ontogeny can be compensated by increased growth or survival later in juvenile life history. Further, fundamental interactions between flow and water temperature must be incorporated into the robust models ultimately required for science-based management. In the absence of such models and data, the current state of science may be sufficient to target specific aspects of flow regimes that are critical to multiple life-history stages, which can then serve as a basis for interim flow prescriptions and subsequent adaptive management.

Forest bioenergy feedstock harvesting effects on water supply

Daniel G. Neary et al. — Mon, 17 Dec 2012 07:23:34 PST

Water flowing from forested catchments, both unmanaged and managed, is highly valued in terms of both quantity and quality. Increasing energy production using wood feedstocks produces varying degrees of impacts and thereby raises concerns about environmental impacts on the highly valued water supply resources of forest ecosystems. The term water supply encompasses both key components of water quantity and water quality. Water quantity considers the amount of increases or decreases, timing, consistency, and relative magnitude of water yields. Plant nutrients (anions and cations), fertilizers, herbicides, ash additions, temperature, dissolved oxygen, pH, bacteria, and sediment comprise water quality. Within the life cycle of forest bioenergy, operational activities during stand establishment, midrotation silviculture, harvesting, product transportation, wood storage, energy production, and ash recycling create variable levels of impacts. Disturbance levels associated with bioenergy operations depend on their type, intensity, frequency, duration, timing, area of extent, and the level of best management practices (BMPs) employed for mitigating of soil disturbances. Feedstock growing, stand tending, harvesting, and wood transportation are considered nonpoint source disturbances since they occur over larger landscapes than energy production activities, which are usually localized at power plants. Water-quantity effects of forest bioenergy production are normally associated with vegetation management and related soil disturbances. Water-quality effects mostly occur as a result of soil disturbances during harvesting, the use of intra-rotation silvicultural chemicals (ash, fertilizers, and herbicides), and inter-rotation site preparation for forest regeneration. Using existing practices designed for environmental protection (BMPs), forest bioenergy programs are completely compatible with maintaining high-quality water supplies in forested catchments.

Adaptive Divergence at the Margin of An Invaded Range

Francis F. Kilkenny et al. — Mon, 17 Dec 2012 07:17:32 PST

Invasive plant species threaten biological communities globally. However, relatively little is known about how evolutionary processes vary over the course of an invasion. To evaluate the importance of historical and adaptive drivers of range expansion, we compare the performance of North American populations of invasive Lonicera japonica from areas established 100–150 years ago, now the southern core of the range, to populations from the northern range margin, established within the last 65 years. Growth and survival of individuals from 17 core and 14 margin populations were compared in common gardens at both regions. After three years, margin plants were larger than core plants regardless of planting region, with 34% more branches and 36% greater biomass. Growth rate was directly related to survival, and margin plants also had 30% greater survival than core plants across both regions. Larger size of individuals from margin populations suggests either that the shorter growing period at the northern margin has selected for more rapid growth or that range expansion has selected for plants with a greater colonizing ability, including rapid establishment and growth. Because this evolution has resulted in enhanced survival and increased growth rate it may drive spread, increasing the likelihood of further invasion.

Area-wide application of verbenone-releasing flakes reduces mortality of whitebark pine Pinus albicaulis caused by the mountain pine beetle Dendroctonus ponderosae

Nancy E. Gillette et al. — Mon, 17 Dec 2012 07:11:34 PST

1 DISRUPT Micro-Flake Verbenone Bark Beetle Anti-Aggregant flakes (Hercon Environmental, Inc., Emigsville, Pennsylvania) were applied in two large-scale tests to assess their efficacy for protecting whitebark pine Pinus albicaulis Engelm. from attack by mountain pine beetle Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae) (MPB). At two locations, five plots of equivalent size and stand structure served as untreated controls. All plots had early- to mid-outbreak beetle populations (i.e. 7.1–29.2 attacked trees/ha). Verbenone was applied at 370 g/ha in both studies. Intercept traps baited with MPB aggregation pheromone were placed near the corners of each plot after the treatment in order to monitor beetle flight within the plots. Trap catches were collected at 7- to 14-day intervals, and assessments were made at the end of the season of stand structure, stand composition and MPB attack rate for the current and previous years.

2 Applications of verbenone flakes significantly reduced the numbers of beetles trapped in treated plots compared with controls at both sites by approximately 50% at the first collection date.

3 The applications also significantly reduced the proportion of trees attacked in both Wyoming and Washington using the proportion of trees attacked the previous year as a covariate in the model for analysis of current year attack rates; in both sites, the reduction was ≥ 50%.

4 The flake formulation of verbenone appears to have promise for area-wide treatment by aerial application when aiming to control the mountain pine beetle in whitebark pine forests.

Effect of Archer Density on Elk Pregnancy Rates and Conception Dates

Gregory A. Davidson et al. — Mon, 17 Dec 2012 06:59:11 PST

Archery hunting in Oregon has increased dramatically over the past 2 decades. At the same time, spring juvenile to adult female ratios of Rocky Mountain elk (Cervus elaphus) have been declining. This has raised concern that archery seasons may be disrupting elk breeding and contributing to the decline in recruitment. Two mechanisms could contribute to reduced juvenile:female ratios: 1) reduced pregnancy rates, and 2) delayed conception dates because of human disturbance during the rut. We varied the number of archery hunters at the Starkey Experimental Forest and Range over 13 years to evaluate effects of archer density on reproduction of elk. Archer densities were maintained at high densities during 4 years (͞x = 1:09 tags sold=km²), low densities during 3 years (͞x = 0.53 tags sold=km²), and no archers during 6 years. We determined pregnancy status, age, kidney fat index (KFI), lactation status, and fetus conception dates for 622 female elk harvested in December. We found pregnancy rate differences of 0.105, 0.080, and 0.021 between high and no archer density years (P = 0.004), high and low archer density years (P = 0.054), and low and no archer density years (P = 0.616), respectively. Conception dates were 4 days later for high archer density compared to low archer density (P = 0.006), but did not differ between high and no archer years (2 days; P = 0.136) or between low and no archer years (2 days; P = 0.108).We compared generalized linear model estimates of pregnancy rates and determined pregnancy rates for 28% of the lactating female elk to be affected by high archer density, whereas archer densities had no significant effect on pregnancy rate estimates for non-lactating females. We found no difference in conception dates among archer densities when comparing model estimates. Our results suggest that archer density and its interaction with nutritional condition of elk influence pregnancy rates of lactating females with low KFI levels; however, the effect of archer density alone does not explain the magnitude of decline in juvenile to female ratios observed in Oregon.

One world, many pathogens!

Kerry O. Britton et al. — Mon, 17 Dec 2012 06:45:36 PST

Forest insect and pathogen species are expanding their geographical ranges through international trade at a rate that most pest specialists and ecologists find alarming. While many invaders are relatively innocuous, several species have damaging impacts on agricultural and natural resources. Furthermore, some of these non-native pests have had catastrophic impacts on ecosystem functions when they invade native communities in which they have no prior evolutionary history. Examples include the demise of chestnut trees in North America, major losses of elms in Europe and North America, Jarrah dieback in Australia, and the devastating effects of pine wood nematode in Asia. Predicting which insects or pathogens will become most problematic and devising mitigation measures to reduce the risk of their arrival and establishment has become the ‘holy grail’ for many entomologists and plant pathologists worldwide. Analysis of historical data is an essential tool for identifying important invasion pathways and weak links in the chain of biosecurity measures that must be strengthened to protect local economies and ecosystem stability. In this issue of New Phytologist, Santini et al. (pp. 238–250), provide a comprehensive and insightful analysis of historical forest pathogen establishment and spread records from Europe. A product of a collaborative (20 nations) European Union-funded project, the paper identifies dominant plant pathogen invasion pathways and key factors predicting pathogen species invasiveness, as well as habitat characteristics that render certain regions more vulnerable to pathogen invasion. All of these associations have implications for preventing future invasions.

In their paper, Santini et al. observed dramatic changes over time in the sources of forest pathogens establishing in Europe. The earliest known pathogen species establishments were largely a result of intra-European spread. North American species first trickled in during the late nineteenth century, and became even more important during the twentieth century. More recently, Asia has become a major source of pathogens. These changes reflect Europe’s expanding sphere of trading partners, particularly for live plant imports, the primary invasion pathway identified in this work and others (Kenis et al., 2007; Liebhold et al., 2012). These observations also suggest a potential ‘invasive species source depletion’ in which a long history of trade with a given source country results in early establishment of many species followed by fewer invasions as the stock of aggressive invaders becomes depleted. However, the authors correctly observe that there is danger associated with new intra- European invasions originating from previously trade-isolated member states, particularly given the lack of trade barriers currently in place within the European Union.

A surprising wealth of exotic pathogen species established in Europe is documented, compared with recent reports from the United States. Aukema et al. (2010) reported only 17 non-native forest tree pathogens established in the United States, whereas Santini et al. found 60 in Europe (only 60 of the 91 pathogens alien to Europe infect forest trees, a criterion used by Aukema et al., 2010). This discrepancy suggests that either taxonomists are more diligent at describing new pathogens in Europe, or perhaps Europe’s long history of colonialism and more extensive planting of non-native trees may contribute to a heavier burden of introduced pathogens in Europe.

Abundance and dynamics of filamentous fungi in the complex ambrosia gardens of the primitively eusocial beetle Xyleborinus saxesenii Ratzeburg (Coleoptera: Curculionidae, Scolytinae)

Peter H.W. Biedermann et al. — Mon, 17 Dec 2012 06:35:04 PST

Insect fungus gardens consist of a community of interacting microorganisms that can have either beneficial or detrimental effects to the farmers. In contrast to fungus-farming ants and termites, the fungal communities of ambrosia beetles and the effects of particular fungal species on the farmers are largely unknown. Here, we used a laboratory rearing technique for studying the filamentous fungal garden community of the ambrosia beetle, Xyleborinus saxesenii, which cultivates fungi in tunnels excavated within dead trees. Raffaelea sulfurea and Fusicolla acetilerea were transmitted in spore-carrying organs by gallery founding females and established first in new gardens. Raffaelea sulfurea had positive effects on egg-laying and larval numbers. Over time, four other fungal species emerged in the gardens. Prevalence of one of them, Paecilomyces variotii, correlated negatively with larval numbers and can be harmful to adults by forming biofilms on their bodies. It also comprised the main portion of garden material removed from galleries by adults. Our data suggest that two mutualistic, several commensalistic and one to two pathogenic filamentous fungi are associated with X. saxesenii. Fungal diversity in gardens of ambrosia beetles appears to be much lower than that in gardens of fungus-culturing ants, which seems to result from essential differences in substrates and behaviours.

Terrestrial biosphere models need better representation of vegetation phenology: results from the North American Carbon Program Site Synthesis

Andrew D. Richardson et al. — Fri, 30 Nov 2012 10:38:56 PST

Phenology, by controlling the seasonal activity of vegetation on the land surface, plays a fundamental role in regulating photosynthesis and other ecosystem processes, as well as competitive interactions and feedbacks to the climate system. We conducted an analysis to evaluate the representation of phenology, and the associated seasonality of ecosystem- scale CO₂ exchange, in 14 models participating in the North American Carbon Program Site Synthesis. Model predictions were evaluated using long-term measurements (emphasizing the period 2000–2006) from 10 forested sites within the AmeriFlux and Fluxnet-Canada networks. In deciduous forests, almost all models consistently predicted that the growing season started earlier, and ended later, than was actually observed; biases of 2 weeks or more were typical. For these sites, most models were also unable to explain more than a small fraction of the observed interannual variability in phenological transition dates. Finally, for deciduous forests, misrepresentation of the seasonal cycle resulted in over-prediction of gross ecosystem photosynthesis by +160 ± 145 g C m^-2 yr^-1 during the spring transition period and +75 ± 130 g C m^-2 yr^-1 during the autumn transition period (13% and 8% annual productivity, respectively) compensating for the tendency of most models to under-predict the magnitude of peak summertime photosynthetic rates. Models did a better job of predicting the seasonality of CO₂ exchange for evergreen forests. These results highlight the need for improved understanding of the environmental controls on vegetation phenology and incorporation of this knowledge into better phenological models. Existing models are unlikely to predict future responses of phenology to climate change accurately and therefore will misrepresent the seasonality and interannual variability of key biosphere–atmosphere feedbacks and interactions in coupled global climate models.

Field validation of Burned Area Reflectance Classification (BARC) products for post fire assessment

Andrew T. Hudak et al. — Fri, 30 Nov 2012 10:04:40 PST

The USFS Remote Sensing Applications Center (RSAC) and the USGS EROS Data Center (EDC) produce Burned Area Reflectance Classification (BARC) maps for use by Burned Area Emergency Rehabilitation (BAER) teams in rapid response to wildfires. BAER teams desire maps indicative of soil burn severity, but photosynthetic and non-photosynthetic vegetation also influences the spectral properties of post-fire imagery. Our objective was to assess burn severity both remotely and on the ground at six 2003 wildfires. We analyzed fire effects data from 34 field sites located across the full range of burn severities observed at the Black Mountain Two, Cooney Ridge, Robert, and Wedge Canyon wildfires in western Montana and the Old and Simi wildfires in southern California. We generated Normalized Burn Ratio (NBR), delta Normalized Burn Ratio (dNBR), and Normalized Difference Vegetation Index (NDVI) indices from Landsat 5, SPOT 4, ASTER, MASTER and MODIS imagery. Pearson correlations between the 44 image and 79 field variables having an absolute value greater than 0.5 were judged meaningful and tabulated in overstory, understory, surface cover, and soil infiltration categories. Vegetation variables produced a higher proportion of meaningful correlations than did surface cover variables, and soil infiltration variables the lowest proportion of meaningful correlations. Soil properties had little measurable influence on NBR, dNBR or NDVI, particularly in low and moderate severity burn areas where unconsumed vegetation occludes background reflectance. BAER teams should consider BARC products much more indicative of post-fire vegetation condition than soil condition. Image acquisition date, in relation to time of field data collection and time since fire, appears to be more important than type of imagery or index used. We recommend preserving the raw NBR or dNBR values in an archived map product to enable remote monitoring of post-fire vegetation recovery. We further recommend that BAER teams rely on the continuous BARC-Adjustable (BARC-A) product (and assign their own severity thresholds as needed) more than the classified BARC product, which oversimplifies highly heterogeneous burn severity characteristics on the ground.

Characterizing Stand- Replacing Harvest and Fire Disturbance Patches in a Forested Landscape: A Case Study from Cooney Ridge, Montana

Andrew T. Hudak et al. — Fri, 30 Nov 2012 10:00:00 PST

In this chapter, we present a case study intended to help crystallize for many readers, through use of an illustrative example, some of the important concepts developed in the preceding chapters. From an understanding of forest successional and disturbance processes, both natural and anthropogenic (Linke et al., Chapter 1, this volume), research questions were developed to compare and contrast the landscape patterns generated from fire and harvest disturbance. Remotely sense data are demonstrated as an appropriate source of relevant information (Coops et al., Chapter 2, this volume), enabling the applications presented for the utilization of change detection approaches for mapping of forest harvest (Healey et al., Chap 3, this volume) and fire (Clark and Bobbe, Chapter 5, this volume). As presented in Chapter 6 (Rogan and Miller, this volume), the use of supportive spatial da sets to aid in the analysis and interpretation of the maps and patterns exhibited demonstrated. The forest harvest and fire maps are subjected to pattern analysis as outlined by Gergel (Chapter 7, this volume), providing insights into the research questions identified.

Predicting Live and Dead Tree Basal Area in Bark Beetle-Affected Forests from Discrete-Return LiDAR

Andrew T. Hudak et al. — Fri, 30 Nov 2012 09:55:42 PST

Recent bark beetle outbreaks in western North America have been widespread and severe. High tree mortality due to bark beetles affects the fundamental ecosystem processes of primary production and decomposition that largely determine carbon balance (Kurz et al. 2008, Pfeifer et al. 2011, Hicke et al. 2012). Forest managers need accurate data on beetle-induced tree mortality to make better decisions on how best to remediate beetle-affected forests and restore healthy ecosystem services (Negron et al. 2008). Discrete-return LiDAR measures canopy height and density, and LiDAR intensity provides some indication of the spectral reflectance and condition of canopy elements (foliage and branches) (Kim et al. 2009). LiDAR has been successfully applied to estimate biomass and carbon stocks in healthy forest (Hudak et al. 2012) and beetle-affected forest (Bright et al. 2012). A challenge in beetle-affected forests is that most airborne LiDAR has a single near infrared wavelength; i.e., LiDAR lacks the multispectral information useful for distinguishing between green, red, and grey trees. However, LiDAR intensity values may help distinguish between live green and dead red or grey trees. Moreover, mountain pine beetles (the most widespread bark beetle currently) and spruce beetles preferentially attack larger trees, so beetles impart a canopy structural signature that may be exploited (Coops et al. 2009).

Our objective is to predict Live and Dead Basal Area (BA) in beetle-affected areas in five states in the USA using canopy height, density, intensity, and topographic metrics derived from discrete-return airborne LiDAR data, tree measurements collected in field plots and summarized into plot-level estimates of Live BA and Dead BA using the Forest Vegetation Simulator (FVS), and the nonparametric Random Forests (RF) machine learning algorithm (Breiman 2001). Predicting both Live and Dead BA in bark beetle-affected forest, where live and dead trees are typically thoroughly mixed, has not been attempted before and should provide insight into the sensitivity of LiDAR to bark beetle effects on coniferous forest canopies.

The roles of nearest neighbor methods in imputing missing data in forest inventory and monitoring databases

Bianca N. I. Eskelson et al. — Fri, 30 Nov 2012 09:49:27 PST

Almost universally, forest inventory and monitoring databases are incomplete, ranging from missing data for only a few records and a few variables, common for small land areas, to missing data for many observations and many variables, common for large land areas. For a wide variety of applications, nearest neighbor (NN) imputation methods have been developed to fill in observations of variables that are missing on some records (Y-variables), using related variables that are available for all records (X-variables). This review attempts to summarize the advantages and weaknesses of NN imputation methods and to give an overview of the NN approaches that have most commonly been used. It also discusses some of the challenges of NN imputation methods. The inclusion of NN imputation methods into standard software packages and the use of consistent notation may improve further development of NN imputation methods. Using X-variables from different data sources provides promising results, but raises the issue of spatial and temporal registration errors. Quantitative measures of the contribution of individual X-variables to the accuracy of imputing the Y-variables are needed. In addition, further research is warranted to verify statistical properties, modify methods to improve statistical properties, and provide variance estimators.