Higher sensitivity and lower specificity in post-fire mortality model validation of 11 western US tree species

2017 ◽  
Vol 26 (5) ◽  
pp. 444 ◽  
Author(s):  
Jeffrey M. Kane ◽  
Phillip J. van Mantgem ◽  
Laura B. Lalemand ◽  
MaryBeth Keifer
Keyword(s):  
Tree Species ◽  
Tree Mortality ◽  
Model Performance ◽  
Mortality Model ◽  
Dead Trees ◽  
Improve Model ◽  
Lower Specificity ◽  
Park Service ◽  
Species Specific ◽  
Higher Sensitivity

Managers require accurate models to predict post-fire tree mortality to plan prescribed fire treatments and examine their effectiveness. Here we assess the performance of a common post-fire tree mortality model with an independent dataset of 11 tree species from 13 National Park Service units in the western USA. Overall model discrimination was generally strong, but performance varied considerably among species and sites. The model tended to have higher sensitivity (proportion of correctly classified dead trees) and lower specificity (proportion of correctly classified live trees) for many species, indicating an overestimation of mortality. Variation in model accuracy (percentage of live and dead trees correctly classified) among species was not related to sample size or percentage observed mortality. However, we observed a positive relationship between specificity and a species-specific bark thickness multiplier, indicating that overestimation was more common in thin-barked species. Accuracy was also quite low for thinner bark classes (<1cm) for many species, leading to poorer model performance. Our results indicate that a common post-fire mortality model generally performs well across a range of species and sites; however, some thin-barked species and size classes would benefit from further refinement to improve model specificity.

scholarly journals An Individual-Tree Mortality Model for Complex Stands of Southeastern British Columbia

2005 ◽  
Vol 20 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Hailemariam Temesgen ◽  
Stephen J. Mitchell
Keyword(s):  
British Columbia ◽  
Tree Species ◽  
Tree Mortality ◽  
Model Development ◽  
Mortality Rates ◽  
Average Deviation ◽  
Individual Tree ◽  
Permanent Sample Plots ◽  
Diameter Increment ◽  
Mortality Model

Abstract An individual-tree mortality model was developed for major tree species in complex stands (multi-cohort, multiaged, and mixed species) of southeastern British Columbia (BC), Canada. Data for 29,773 trees were obtained from permanent sample plots established in BC. Average annual diameter increment and mortality rates ranged from 0.08 to 0.17 cm/year and from 0.3 to 2.6%, respectively. Approximately 70% of the trees were used for model development and 30% for model evaluation. After evaluating the model, all 29,773 trees were used to fit the final model. A generalized logistic model was used to relate mortality to tree size, competition, and relative position of trees in a stand. The evaluation test demonstrated that the model appears to be well behaved and robust for the tree species considered in this study. For the eight tree species, the average deviation between observed and predicted annual mortality rates varied from −0.5 to 0.7% in the test data. West. J. Appl. For. 20(2):101–109.

scholarly journals Background mortality drivers of European tree species: climate change matters

2019 ◽  
Vol 286 (1900) ◽  
pp. 20190386 ◽  
Author(s):  
Adrien Taccoen ◽  
Christian Piedallu ◽  
Ingrid Seynave ◽  
Vincent Perez ◽  
Anne Gégout-Petit ◽  
...  
Keyword(s):  
Climate Change ◽  
Tree Species ◽  
Tree Mortality ◽  
Forest Tree ◽  
Climate Change Signal ◽  
Dead Trees ◽  
Background Mortality ◽  
Increasing Temperature ◽  
The Impact ◽  
Stand Characteristics

Increases in tree mortality rates have been highlighted in different biomes over the past decades. However, disentangling the effects of climate change on the temporal increase in tree mortality from those of management and forest dynamics remains a challenge. Using a modelling approach taking tree and stand characteristics into account, we sought to evaluate the impact of climate change on background mortality for the most common European tree species. We focused on background mortality, which is the mortality observed in a stand in the absence of abrupt disturbances, to avoid confusion with mortality events unrelated to long-term changes in temperature and rainfall. We studied 372 974 trees including 7312 dead trees from forest inventory data surveyed across France between 2009 and 2015. Factors related to competition, stand characteristics, management intensity, and site conditions were the expected preponderant drivers of mortality. Taking these main drivers into account, we detected a climate change signal on 45% of the 43 studied species, explaining an average 6% of the total modelled mortality. For 18 out of the 19 species sensitive to climate change, we evidenced greater mortality with increasing temperature or decreasing rainfall. By quantifying the mortality excess linked to the current climate change for European temperate forest tree species, we provide new insights into forest vulnerability that will prove useful for adapting forest management to future conditions.

scholarly journals Effect of different tree mortality patterns on stand development in the forest model SIBYLA

2016 ◽  
Vol 62 (3) ◽  
pp. 173-180
Author(s):  
Jiří Trombik ◽  
Ivan Barka ◽  
Tomáš Hlásny
Keyword(s):  
Bark Beetle ◽  
Tree Species ◽  
Bark Beetles ◽  
Tree Mortality ◽  
Stand Structure ◽  
Random Pattern ◽  
Forest Stands ◽  
Tree Species Composition ◽  
Dead Trees ◽  
Related Mortality

Abstract Forest mortality critically affects stand structure and the quality of ecosystem services provided by forests. Spruce bark beetle (Ips typographus) generates rather complex infestation and mortality patterns, and implementation of such patterns in forest models is challenging. We present here the procedure, which allows to simulate the bark beetle-related tree mortality in the forest dynamics model Sibyla. We explored how sensitive various production and stand structure indicators are to tree mortality patterns, which can be generated by bark beetles. We compared the simulation outputs for three unmanaged forest stands with 40, 70 and 100% proportion of spruce as affected by the disturbance-related mortality that occurred in a random pattern and in a patchy pattern. The used tree species and age class-specific mortality rates were derived from the disturbance-related mortality records from Slovakia. The proposed algorithm was developed in the SQLite using the Python language, and the algorithm allowed us to define the degree of spatial clustering of dead trees ranging from a random distribution to a completely clustered distribution; a number of trees that died in either mode is set to remain equal. We found significant differences between the long-term developments of the three investigated forest stands, but we found very little effect of the tested mortality modes on stand increment, tree species composition and diversity, and tree size diversity. Hence, our hypothesis that the different pattern of dead trees emergence should affect the competitive interactions between trees and regeneration, and thus affect selected productivity and stand structure indicators was not confirmed.

Species Specific Immunoassays to Measure Blood Platelet and Coagulation Activation in the Rat

1996 ◽  
Vol 76 (06) ◽  
pp. 1090-1095 ◽  
Author(s):  
C Ravanat ◽  
M Freund ◽  
S Schuhler ◽  
P Grunert ◽  
L Meyer ◽  
...  
Keyword(s):  
Antithrombin Iii ◽  
Plasma Concentrations ◽  
Simultaneous Detection ◽  
Blood Platelet ◽  
Coagulation Activation ◽  
Platelet Factor ◽  
Prethrombotic State ◽  
Low Levels ◽  
Species Specific ◽  
Higher Sensitivity

SummaryThe purpose of this study was to develop specific and sensitive immunoassays to detect early indices of hypercoagulability in the rat. Rat platelet factor 4 (rPF4) and rat fibrinopeptide A (rFPA) assays, tools for the detection of activation of platelets and coagulation respectively, were designed using antibodies raised against purified rPF4 and against synthetic rFPA. The relevance of these new assays and of the commercially available ELISA kit for thrombin-antithrombin III (TAT) complexes was demonstrated in a rat model of a prethrombotic state induced by intravenous infusion of varying doses of thromboplastin (90 to 2400 μl/kg/h). In this model, the immunoassays allowed simultaneous detection of low levels of rFPA and rPF4 which were correlated with fibrinogen and platelet consumption and TAT generation and further proved to be of higher sensitivity than the classical methods of platelet count or measurement of fibrinogen levels. Plasma concentrations of rFPA, rPF4 and TAT were dependent on infusion time and thromboplastin dose, while hirudin (1 mg/kg) prevented their appearance. Thus the new specific immunoassays for rPF4 and rFPA and the commercial human TAT assay represent useful tools for pathophysiological studies or the screening of antithrombotic drugs in rats.

scholarly journals Classification of Tree Species as Well as Standing Dead Trees Using Triple Wavelength ALS in a Temperate Forest

2019 ◽  
Vol 11 (22) ◽  
pp. 2614 ◽  
Author(s):  
Nina Amiri ◽  
Peter Krzystek ◽  
Marco Heurich ◽  
Andrew Skidmore
Keyword(s):  
Tree Species ◽  
Feature Selection Method ◽  
Silver Fir ◽  
Maximum Point ◽  
Individual Tree ◽  
Dead Trees ◽  
Multi Wavelength ◽  
Standing Dead ◽  
Standing Dead Trees ◽  
532 Nm

Knowledge about forest structures, particularly of deadwood, is fundamental for understanding, protecting, and conserving forest biodiversity. While individual tree-based approaches using single wavelength airborne laserscanning (ALS) can successfully distinguish broadleaf and coniferous trees, they still perform multiple tree species classifications with limited accuracy. Moreover, the mapping of standing dead trees is becoming increasingly important for damage calculation after pest infestation or biodiversity assessment. Recent advances in sensor technology have led to the development of new ALS systems that provide up to three different wavelengths. In this study, we present a novel method which classifies three tree species (Norway spruce, European beech, Silver fir), and dead spruce trees with crowns using full waveform ALS data acquired from three different sensors (wavelengths 532 nm, 1064 nm, 1550 nm). The ALS data were acquired in the Bavarian Forest National Park (Germany) under leaf-on conditions with a maximum point density of 200 points/m 2 . To avoid overfitting of the classifier and to find the most prominent features, we embed a forward feature selection method. We tested our classification procedure using 20 sample plots with 586 measured reference trees. Using single wavelength datasets, the highest accuracy achieved was 74% (wavelength = 1064 nm), followed by 69% (wavelength = 1550 nm) and 65% (wavelength = 532 nm). An improvement of 8–17% over single wavelength datasets was achieved when the multi wavelength data were used. Overall, the contribution of the waveform-based features to the classification accuracy was higher than that of the geometric features by approximately 10%. Our results show that the features derived from a multi wavelength ALS point cloud significantly improve the detailed mapping of tree species and standing dead 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 Over half of western United States' most abundant tree species in decline

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hunter Stanke ◽  
Andrew O. Finley ◽  
Grant M. Domke ◽  
Aaron S. Weed ◽  
David W. MacFarlane
Keyword(s):  
United States ◽  
Tree Species ◽  
Tree Mortality ◽  
Temperate Forests ◽  
Size Structure ◽  
Forest Disturbance ◽  
Population Decline ◽  
Western United States ◽  
Scale Transformation ◽  
Forest Composition

AbstractChanging forest disturbance regimes and climate are driving accelerated tree mortality across temperate forests. However, it remains unknown if elevated mortality has induced decline of tree populations and the ecological, economic, and social benefits they provide. Here, we develop a standardized forest demographic index and use it to quantify trends in tree population dynamics over the last two decades in the western United States. The rate and pattern of change we observe across species and tree size-distributions is alarming and often undesirable. We observe significant population decline in a majority of species examined, show decline was particularly severe, albeit size-dependent, among subalpine tree species, and provide evidence of widespread shifts in the size-structure of montane forests. Our findings offer a stark warning of changing forest composition and structure across the western US, and suggest that sustained anthropogenic and natural stress will likely result in broad-scale transformation of temperate forests globally.

scholarly journals Towards Robust Representations of Spatial Networks Using Graph Neural Networks

2021 ◽  
Vol 11 (15) ◽  
pp. 6918
Author(s):  
Chidubem Iddianozie ◽  
Gavin McArdle
Keyword(s):  
Machine Learning ◽  
Model Performance ◽  
Network Models ◽  
Data Representation ◽  
Spatial Networks ◽  
Neural Network Models ◽  
Improve Model ◽  
Graph Neural Networks ◽  
Spatial Entities ◽  
Improve Model Performance

The effectiveness of a machine learning model is impacted by the data representation used. Consequently, it is crucial to investigate robust representations for efficient machine learning methods. In this paper, we explore the link between data representations and model performance for inference tasks on spatial networks. We argue that representations which explicitly encode the relations between spatial entities would improve model performance. Specifically, we consider homogeneous and heterogeneous representations of spatial networks. We recognise that the expressive nature of the heterogeneous representation may benefit spatial networks and could improve model performance on certain tasks. Thus, we carry out an empirical study using Graph Neural Network models for two inference tasks on spatial networks. Our results demonstrate that heterogeneous representations improves model performance for down-stream inference tasks on spatial networks.

scholarly journals Population Pharmacokinetics of Doxycycline in Children

2019 ◽  
Vol 63 (12) ◽  
Author(s):  
Elizabeth J. Thompson ◽  
Huali Wu ◽  
Chiara Melloni ◽  
Stephen Balevic ◽  
Janice E. Sullivan ◽  
...  
Keyword(s):  
Model Performance ◽  
Standard Of Care ◽  
Volume Of Distribution ◽  
Clinical Value ◽  
Final Model ◽  
Childhood Infections ◽  
Obesity Status ◽  
Improve Model ◽  
Using Data ◽  
Improve Model Performance

ABSTRACT Doxycycline is a tetracycline-class antimicrobial labeled by the U.S. Food and Drug Administration for children >8 years of age for many common childhood infections. Doxycycline is not labeled for children ≤8 years of age, due to the association between tetracycline-class antibiotics and tooth staining, although doxycycline may be used off-label under severe conditions. Accordingly, there is a paucity of pharmacokinetic (PK) data to guide dosing in children 8 years and younger. We leveraged opportunistically collected plasma samples after intravenous (i.v.) and oral doxycycline doses received per standard of care to characterize the PK of doxycycline in children of different ages and evaluated the effect of obesity and fasting status on PK parameters. We developed a population PK model of doxycycline using data collected from 47 patients 0 to 18 years of age, including 14 participants ≤8 years. We developed a 1-compartment PK model and found doxycycline clearance to be 3.32 liters/h/70 kg of body weight and volume to be 96.8 liters/70 kg for all patients, comparable to values reported in adults. We estimated a bioavailability of 89.6%, also consistent with adult data. Allometrically scaled clearance and volume of distribution did not differ between children 2 to ≤8 years of age and children >8 to ≤18 years of age, suggesting that younger children may be given the same per-kilogram dosing. Obesity status and fasting status were not selected for inclusion in the final model. Additional doxycycline PK samples collected in future studies may be used to improve model performance and maximize its clinical value.

Impact of Deer Browsing on Regeneration in Mixed Stands in Southern New England

1995 ◽  
Vol 12 (3) ◽  
pp. 115-120 ◽  
Author(s):  
David B. Kittredge ◽  
P. Mark S. Ashton
Keyword(s):  
New England ◽  
Tree Species ◽  
Sugar Maple ◽  
Red Maple ◽  
White Pine ◽  
Mixed Stands ◽  
Tree Species Composition ◽  
Southern New England ◽  
Pine Seedlings ◽  
Species Specific

Abstract Browsing preferences by white-tailed deer were evaluated for 6 tree species in northeastern Connecticut. Deer density averaged 23/mile². Deer exhibited no species-specific preferences for seedlings greater than 19 in. For seedlings less than 19 in., hemlock and black birch were preferred. Red maple, sugar maple, and white pine seedlings were avoided. Red oak seedlings were neither preferred nor avoided. A much higher proportion of seedlings greater than 19.7 in. in height was browsed, regardless of species. Browsing preferences for species in the smaller seedling class, combined with a lack of preference for species in the larger class may result in future stands with less diverse tree species composition. Deer densities in excess of 23/mile² may be incompatible with regeneration of diverse forests in southern New England. North. J. Appl. For. 12(3):115-120.

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