scholarly journals Multi-scale assessment of post-fire tree mortality models

2019 ◽  
Vol 28 (1) ◽  
pp. 46 ◽  
Author(s):  
Tucker J. Furniss ◽  
Andrew J. Larson ◽  
Van R. Kane ◽  
James A. Lutz
Keyword(s):  
Spatial Pattern ◽  
Sierra Nevada ◽  
Tree Mortality ◽  
Spatial Scales ◽  
Large Diameter ◽  
Fire Effects ◽  
Point Pattern ◽  
Individual Tree ◽  
Mortality Models ◽  
Rim Fire

Post-fire tree mortality models are vital tools used by forest land managers to predict fire effects, estimate delayed mortality and develop management prescriptions. We evaluated the performance of mortality models within the First Order Fire Effects Model (FOFEM) software, and compared their performance to locally-parameterised models based on five different forms. We evaluated all models at the individual tree and stand levels with a dataset comprising 34174 trees from a mixed-conifer forest in the Sierra Nevada, California that burned in the 2013 Rim Fire. We compared stand-level accuracy across a range of spatial scales, and we used point pattern analysis to test the accuracy with which mortality models predict post-fire tree spatial pattern. FOFEM under-predicted mortality for the three conifers, possibly because of the timing of the Rim Fire during a severe multi-year drought. Locally-parameterised models based on crown scorch were most accurate in predicting individual tree mortality, but tree diameter-based models were more accurate at the stand level for Abies concolor and large-diameter Pinus lambertiana, the most abundant trees in this forest. Stand-level accuracy was reduced by spatially correlated error at small spatial scales, but stabilised at scales ≥1ha. The predictive error of FOFEM generated inaccurate predictions of post-fire spatial pattern at small scales, and this error could be reduced by improving FOFEM model accuracy for small trees.

scholarly journals A large database supports the use of simple models of post-fire tree mortality for thick-barked conifers, with less support for other species

Fire Ecology ◽  
2020 ◽  
Vol 16 (1) ◽  
Author(s):  
C. Alina Cansler ◽  
Sharon M. Hood ◽  
Phillip J. van Mantgem ◽  
J. Morgan Varner
Keyword(s):  
Tree Mortality ◽  
Characteristic Curve ◽  
Small Diameter ◽  
Fire Effects ◽  
Tree Level ◽  
Clear Understanding ◽  
Bark Thickness ◽  
Mortality Models ◽  
Species Specific ◽  
Stem Mortality

Abstract Background Predictive models of post-fire tree and stem mortality are vital for management planning and understanding fire effects. Post-fire tree and stem mortality have been traditionally modeled as a simple empirical function of tree defenses (e.g., bark thickness) and fire injury (e.g., crown scorch). We used the Fire and Tree Mortality database (FTM)—which includes observations of tree mortality in obligate seeders and stem mortality in basal resprouting species from across the USA—to evaluate the accuracy of post-fire mortality models used in the First Order Fire Effects Model (FOFEM) software system. The basic model in FOFEM, the Ryan and Amman (R-A) model, uses bark thickness and percentage of crown volume scorched to predict post-fire mortality and can be applied to any species for which bark thickness can be calculated (184 species-level coefficients are included in the program). FOFEM (v6.7) also includes 38 species-specific tree mortality models (26 for gymnosperms, 12 for angiosperms), with unique predictors and coefficients. We assessed accuracy of the R-A model for 44 tree species and accuracy of 24 species-specific models for 13 species, using data from 93 438 tree-level observations and 351 fires that occurred from 1981 to 2016. Results For each model, we calculated performance statistics and provided an assessment of the representativeness of the evaluation data. We identified probability thresholds for which the model performed best, and the best thresholds with either ≥80% sensitivity or specificity. Of the 68 models evaluated, 43 had Area Under the Receiver Operating Characteristic Curve (AUC) values ≥0.80, indicating excellent performance, and 14 had AUCs <0.7, indicating poor performance. The R-A model often over-predicted mortality for angiosperms; 5 of 11 angiosperms had AUCs <0.7. For conifers, R-A over-predicted mortality for thin-barked species and for small diameter trees. The species-specific models had significantly higher AUCs than the R-A models for 10 of the 22 models, and five additional species-specific models had more balanced errors than R-A models, even though their AUCs were not significantly different or were significantly lower. Conclusions Approximately 75% of models tested had acceptable, excellent, or outstanding predictive ability. The models that performed poorly were primarily models predicting stem mortality of angiosperms or tree mortality of thin-barked conifers. This suggests that different approaches—such as different model forms, better estimates of bark thickness, and additional predictors—may be warranted for these taxa. Future data collection and research should target the geographical and taxonomic data gaps and poorly performing models identified in this study. Our evaluation of post-fire tree mortality models is the most comprehensive effort to date and allows users to have a clear understanding of the expected accuracy in predicting tree death from fire for 44 species.

scholarly journals Climatic information improves statistical individual-tree mortality models for three key species of Sichuan Province, China

2015 ◽  
Vol 72 (4) ◽  
pp. 443-455 ◽  
Author(s):  
Shuai Qiu ◽  
Ming Xu ◽  
Renqiang Li ◽  
Yunpu Zheng ◽  
Daniel Clark ◽  
...  
Keyword(s):  
Tree Mortality ◽  
Sichuan Province ◽  
Individual Tree ◽  
Mortality Models ◽  
Key Species ◽  
Climatic Information

scholarly journals Spatial Pattern Analysis of Sharka Disease (Plum pox virus Strain M) in Peach Orchards of Southern France

2003 ◽  
Vol 93 (12) ◽  
pp. 1543-1552 ◽  
Author(s):  
Sylvie Dallot ◽  
Tim Gottwald ◽  
Gérard Labonne ◽  
Jean-Bernard Quiot
Keyword(s):  
Spatial Pattern ◽  
Spatial Patterns ◽  
Disease Incidence ◽  
Point Pattern ◽  
Plum Pox Virus ◽  
Spatial Pattern Analysis ◽  
Individual Tree ◽  
Southern France ◽  
Wide Range ◽  
Sharka Disease

The spatial pattern of Sharka disease, caused by Plum pox virus (PPV) strain M, was investigated in 18 peach plots located in two areas of southern France. PPV infections were monitored visually for each individual tree during one to three consecutive years. Point pattern and correlation-type approaches were undertaken using the binary data directly or after parsing them in contiguous quadrats of 4, 9, and 16 trees. Ordinary runs generally revealed a low but variable proportion of rows with adjacent symptomatic trees. Aggregation of disease incidence was indicated by the θ parameter of the beta-binomial distribution and related indices in 15 of the 18 plots tested for at least one assessment date of each. When aggregation was detected, it was indicated at all quadrat sizes and tended to be a function of disease incidence, as shown by the binary form of Taylor's power law. Spatial analysis by distance indices (SADIE) showed a nonrandom arrangement of quadrats with infected trees in 14 plots. The detection of patch clusters enclosing quadrats with above-average density of symptomatic trees, ellipsoidal in shape and generally extending from 4 to 14 trees within rows and from 4 to 10 trees perpendicular to the rows, could be interpreted as local areas of influence of PPV spread. Spatial patterns at the plot scale were often characterized by the occurrence of several clusters of infected trees located up to 90 m apart in the direction of the rows. When several time assessments were available, increasing clustering over time was generally evidenced by stronger values of the clustering index and by increasing patch cluster size. The combination of the different approaches revealed a wide range of spatial patterns of PPV-M, from no aggregation to high aggregation of symptomatic trees at all spatial scales investigated. Such patterns suggested that aphid transmission to neighboring trees occurred frequently but was not systematic. The mechanism of primary virus introduction, the age and structure of the orchards when infected, and the diversity of vector species probably had a strong influence on the secondary spread of the disease. This study provides a more complete understanding of PPV-M patterns which could help to improve targeting of removal of PPV-infected trees for more effective disease control.

Extending the range of applicability of an individual tree mortality model

1990 ◽  
Vol 20 (8) ◽  
pp. 1212-1218 ◽  
Author(s):  
David A. Hamilton Jr.
Keyword(s):  
Tree Mortality ◽  
Data Sets ◽  
Habitat Types ◽  
Individual Tree ◽  
Independent Variables ◽  
Mortality Model ◽  
Mortality Models ◽  
Range Of Values

Limits are frequently encountered in the range of values of independent variables included in data sets used to develop individual tree mortality models. If the resulting model is to be utilized, its ability to extrapolate to conditions outside these limits must be evaluated. This paper describes the development and evaluation of six assumptions required to extend the range of applicability of an individual tree mortality model previously described. The assumptions deal with mortality in very dense stands, mortality for very small trees, mortality on habitat types and regions poorly represented in the data, and mortality for species poorly represented in the data.

scholarly journals Forest Resistance to Extended Drought Enhanced by Prescribed Fire in Low Elevation Forests of the Sierra Nevada

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1248
Author(s):  
Phillip J. van Mantgem ◽  
Anthony C. Caprio ◽  
Nathan L. Stephenson ◽  
Adrian J. Das
Keyword(s):  
Sierra Nevada ◽  
National Parks ◽  
Prescribed Fire ◽  
Ponderosa Pine ◽  
Tree Mortality ◽  
Early Years ◽  
Current Evidence ◽  
Stem Density ◽  
Individual Tree ◽  
Sugar Pine

Prescribed fire reduces fire hazards by removing dead and live fuels (small trees and shrubs). Reductions in forest density following prescribed fire treatments (often in concert with mechanical treatments) may also lessen competition so that residual trees might be more likely to survive when confronted with additional stressors, such as drought. The current evidence for these effects is mixed and additional study is needed. Previous work found increased tree survivorship in low elevation forests with a recent history of fire during the early years of an intense drought (2012 to 2014) in national parks in the southern Sierra Nevada. We extend these observations through additional years of intense drought and continuing elevated tree mortality through 2017 at Sequoia and Kings Canyon National Parks. Relative to unburned sites, we found that burned sites had lower stem density and had lower proportions of recently dead trees (for stems ≤47.5 cm dbh) that presumably died during the drought. Differences in recent tree mortality among burned and unburned sites held for both fir (white fir and red fir) and pine (sugar pine and ponderosa pine) species. Unlike earlier results, models of individual tree mortality probability supported an interaction between plot burn status and tree size, suggesting the effect of prescribed fire was limited to small trees. We consider differences with other recent results and discuss potential management implications including trade-offs between large tree mortality following prescribed fire and increased drought resistance.

Initial tree mortality and insect and pathogen response to fire and thinning restoration treatments in an old-growth mixed-conifer forest of the Sierra Nevada, California

2008 ◽  
Vol 38 (12) ◽  
pp. 3011-3020 ◽  
Author(s):  
Patricia E. Maloney ◽  
Thomas F. Smith ◽  
Camille E. Jensen ◽  
Jim Innes ◽  
David M. Rizzo ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Forest Restoration ◽  
Tree Mortality ◽  
Large Diameter ◽  
Heterobasidion Annosum ◽  
White Pine Blister Rust ◽  
Mixed Conifer ◽  
White Pine ◽  
Dwarf Mistletoe ◽  
Blister Rust

Fire and thinning restoration treatments in fire-suppressed forests often damage or stress leave trees, altering pathogen and insect affects. We compared types of insect- and pathogen-mediated mortality on mixed-conifer trees 3 years after treatment. The number of bark beetle attacked trees was greater in burn treatments compared with no-burn treatments, and in some cases, larger pine trees were preferentially attacked. Restoration treatments are not expected to change the trajectory of spread and intensification of dwarf mistletoe. Thinning treatments may have provided a sanitation effect in which large leave trees have lower levels of dwarf mistletoe. Although thinning treatments are known to exacerbate root disease, <12% of cut stumps were infected with root pathogens ( Armillaria gallica and Heterobasidion annosum ). Treatments increased Ribes (alternate host for white pine blister rust) frequency and abundance, which may have very localized impacts on white pine blister rust dynamics. In some instances, fire, insects, and pathogens appear to conflict with forest restoration goals by reducing the percentage of pine and producing proportionally higher rates of tree mortality in large-diameter size classes. To better understand the long-term effects of restoration treatments on pathogens and insects, continued monitoring over the course of varying climatic conditions will be needed.

Rice straw mulch for post-fire erosion control: assessing non-target effects on vegetation communities

2017 ◽  
Vol 26 (6) ◽  
pp. 538 ◽  
Author(s):  
Kristen L. Shive ◽  
Becky L. Estes ◽  
Angela M. White ◽  
Hugh D. Safford ◽  
Kevin L. O'Hara ◽  
...  
Keyword(s):  
Rice Straw ◽  
Sierra Nevada ◽  
Native Species ◽  
Tree Mortality ◽  
Plant Cover ◽  
Erosion Control ◽  
Straw Mulch ◽  
Burned Areas ◽  
Rim Fire ◽  
And Control

Straw mulch is commonly used for post-fire erosion control in severely burned areas but this practice can introduce non-native species, even when certified weed-free straw is used. Rice straw has recently been promoted as an alternative to wheat under the hypothesis that non-native species that are able to grow in a rice field are unlikely to establish in dry forested habitats. We investigated this hypothesis in the severely burned areas of the 2013 Rim Fire in the Sierra Nevada that were treated with rice straw post-fire. In 2014, we installed 134 plots in mulched and control areas with >95% tree mortality and re-measured a subsample in 2015. Mulched areas had significantly higher non-native forb cover, non-native graminoid cover and non-native species richness. In addition, 25 non-native species occurred exclusively in mulched areas; collectively, these responses contributed to more homogenous plant communities in mulched areas than in unmulched areas in 2015. In contrast, mulch had no effect on total plant cover, and conifer regeneration densities were generally unaffected with the exception of a slight positive effect on Douglas-fir. We recommend more stringent testing for weed-free certification and that funding for non-native species eradication be included with post-fire rehabilitation plans.

scholarly journals Genomic variation in the American pika: signatures of geographic isolation and implications for conservation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Kelly B. Klingler ◽  
Joshua P. Jahner ◽  
Thomas L. Parchman ◽  
Chris Ray ◽  
Mary M. Peacock
Keyword(s):  
Genetic Variation ◽  
Genetic Structure ◽  
Sierra Nevada ◽  
Spatial Genetic Structure ◽  
Spatial Scales ◽  
Thermal Sensitivity ◽  
Genomic Variation ◽  
Genome Wide ◽  
A Genome ◽  
American Pika

Abstract Background Distributional responses by alpine taxa to repeated, glacial-interglacial cycles throughout the last two million years have significantly influenced the spatial genetic structure of populations. These effects have been exacerbated for the American pika (Ochotona princeps), a small alpine lagomorph constrained by thermal sensitivity and a limited dispersal capacity. As a species of conservation concern, long-term lack of gene flow has important consequences for landscape genetic structure and levels of diversity within populations. Here, we use reduced representation sequencing (ddRADseq) to provide a genome-wide perspective on patterns of genetic variation across pika populations representing distinct subspecies. To investigate how landscape and environmental features shape genetic variation, we collected genetic samples from distinct geographic regions as well as across finer spatial scales in two geographically proximate mountain ranges of eastern Nevada. Results Our genome-wide analyses corroborate range-wide, mitochondrial subspecific designations and reveal pronounced fine-scale population structure between the Ruby Mountains and East Humboldt Range of eastern Nevada. Populations in Nevada were characterized by low genetic diversity (π = 0.0006–0.0009; θW = 0.0005–0.0007) relative to populations in California (π = 0.0014–0.0019; θW = 0.0011–0.0017) and the Rocky Mountains (π = 0.0025–0.0027; θW = 0.0021–0.0024), indicating substantial genetic drift in these isolated populations. Tajima’s D was positive for all sites (D = 0.240–0.811), consistent with recent contraction in population sizes range-wide. Conclusions Substantial influences of geography, elevation and climate variables on genetic differentiation were also detected and may interact with the regional effects of anthropogenic climate change to force the loss of unique genetic lineages through continued population extirpations in the Great Basin and Sierra Nevada.

scholarly journals Cross-scale interaction of host tree size and climatic water deficit governs bark beetle-induced tree mortality

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michael J. Koontz ◽  
Andrew M. Latimer ◽  
Leif A. Mortenson ◽  
Christopher J. Fettig ◽  
Malcolm P. North
Keyword(s):  
Water Deficit ◽  
Sierra Nevada ◽  
Bark Beetle ◽  
Ponderosa Pine ◽  
Tree Mortality ◽  
Mortality Rates ◽  
Dendroctonus Brevicomis ◽  
Scale Interactions ◽  
Climatic Water Deficit ◽  
Host Mortality

AbstractThe recent Californian hot drought (2012–2016) precipitated unprecedented ponderosa pine (Pinus ponderosa) mortality, largely attributable to the western pine beetle (Dendroctonus brevicomis; WPB). Broad-scale climate conditions can directly shape tree mortality patterns, but mortality rates respond non-linearly to climate when local-scale forest characteristics influence the behavior of tree-killing bark beetles (e.g., WPB). To test for these cross-scale interactions, we conduct aerial drone surveys at 32 sites along a gradient of climatic water deficit (CWD) spanning 350 km of latitude and 1000 m of elevation in WPB-impacted Sierra Nevada forests. We map, measure, and classify over 450,000 trees within 9 km2, validating measurements with coincident field plots. We find greater size, proportion, and density of ponderosa pine (the WPB host) increase host mortality rates, as does greater CWD. Critically, we find a CWD/host size interaction such that larger trees amplify host mortality rates in hot/dry sites. Management strategies for climate change adaptation should consider how bark beetle disturbances can depend on cross-scale interactions, which challenge our ability to predict and understand patterns of tree mortality.

scholarly journals Occurrence of tuberculosis cases in Crato, Ceará, from 2002 to 2011: a spatial analisys of specific standards

2015 ◽  
Vol 18 (2) ◽  
pp. 313-325 ◽  
Author(s):  
Mayrla Lima Pinto ◽  
Talina Carla da Silva ◽  
Lidiane Cristina Félix Gomes ◽  
Maria Rita Bertolozzi ◽  
Lourdes Milagros Mendoza Villavicencio ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Spatial Pattern ◽  
Urban Area ◽  
Temporal Trend ◽  
Kernel Method ◽  
Quantitative Approach ◽  
Point Pattern ◽  
Hybrid Design ◽  
Population Densities ◽  
Population Groups

OBJECTIVE: to analyze the spatial distribution of tuberculosis in Crato, Ceará, Brazil, from 2002 to 2011, aiming to check for a point pattern. METHODS: This is an ecological, temporal trend and hybrid design study, with a quantitative approach. A total of 261 cases of tuberculosis were geo-referenced and 20 (7.1%) were considered as losses due to the lack of address. The profile of patients in 10 years of study was in accordance with the following pattern: men aged between 20 and 59 years, with low schooling, affected by the pulmonary form of tuberculosis and who were cured from the disease. RESULTS: The analysis of the spatial distribution of tuberculosis points out that in the period of study, new cases of the disease were not distributed on a regular basis, indicating a clustered spatial pattern, confirmed by the L-function. The map with the density of new cases estimated by the Kernel method showed that the "hot" areas are more concentrated in the vicinity of the central urban area. CONCLUSION: The study allowed pointing out areas of higher and lower concentration of tuberculosis, identifying the spatial pattern, but it also recognized that the disease has not reached all of the population groups with the same intensity. Those who were most vulnerable were the ones who lived in regions with higher population densities, precarious living conditions, and with intense flow of people.

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