scholarly journals Bayesian calibration of a growth‐dependent tree mortality model to simulate the dynamics of European temperate forests

2019 ◽  
Vol 30 (1) ◽  
Author(s):  
Maxime Cailleret ◽  
Nicolas Bircher ◽  
Florian Hartig ◽  
Lisa Hülsmann ◽  
Harald Bugmann
Keyword(s):  
Tree Mortality ◽  
Temperate Forests ◽  
Bayesian Calibration ◽  
Mortality Model

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 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.

TRIPLEX-Mortality model for simulating drought-induced tree mortality in boreal forests: Model development and evaluation

2021 ◽  
Vol 455 ◽  
pp. 109652
Author(s):  
Qiuyu Liu ◽  
Changhui Peng ◽  
Robert Schneider ◽  
Dominic Cyr ◽  
Zelin Liu ◽  
...  
Keyword(s):  
Boreal Forests ◽  
Tree Mortality ◽  
Model Development ◽  
Mortality Model

scholarly journals Resilience of Resprouting Temperate Forests is Diminished by Coupled Severe Drought and Fire

2021 ◽  
Author(s):  
Eli Ryan Bendall ◽  
Michael Bedward ◽  
Matthias Boer ◽  
Hamish Clarke ◽  
Luke Collins ◽  
...  
Keyword(s):  
Tree Mortality ◽  
Seedling Recruitment ◽  
Temperate Forests ◽  
Dry Forest ◽  
Drought Severity ◽  
Severe Drought ◽  
Forest Types ◽  
Juvenile Mortality ◽  
Moderate Drought ◽  
Effects Of Drought

Abstract Elevated tree mortality and reduced recruitment of new trees linked to drought and fires has been reported across a range of forests over the last few decades. Forests that resprout new foliage epicormically from buds beneath the bark are considered highly resilient to disturbance, but are potentially at risk of elevated mortality, demographic shifts and changes to species composition due to synergistic effects of drought and fire. Despite this, the effects of drought-fire interactions on such forests remain largely unknown. We assessed the effects of drought severity and fire frequency on juvenile mortality, post-fire seedling recruitment and replacement of juvenile trees (balance of recruitment minus mortality) following fire. We compared dry ridgetop and wet gully assemblages across a temperate forest in southern Australia. Both forest types experienced higher rates of fire-induced juvenile mortality in areas that had experienced severe drought compared to moderate drought, though mortality rates were generally low across all drought and fire combinations. This result indicated that topographic position (i.e. wet gullies) did little to moderate juvenile mortality when exposed to severe drought plus fire. In wet forest, severe drought also reduced recruitment and replacement of dead juveniles by post-fire seedlings compared to moderate drought. In dry forest net-negative replacement increased with the severity of drought. Across both forest types, the total pool of juveniles was reduced under severe drought. Future increases in the frequency of coupled severe drought and fire will likely increase the susceptibility of resilient temperate forests to major changes in structure and function.

scholarly journals Bayesian calibration of a soil organic carbon model using Δ<sup>14</sup>C measurements of soil organic carbon and heterotrophic respiration as joint constraints

2013 ◽  
Vol 10 (8) ◽  
pp. 13803-13854
Author(s):  
B. Ahrens ◽  
M. Reichstein ◽  
W. Borken ◽  
J. Muhr ◽  
S. E. Trumbore ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Respiration ◽  
Temperate Forests ◽  
Heterotrophic Respiration ◽  
Parameter Estimates ◽  
Observational Constraints ◽  
Multiple Constraints ◽  
Bayesian Calibration ◽  
The Usa

Abstract. Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO2. Soil organic carbon (SOC) turnover has been studied using the Δ14C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ14C values of CO2 evolved during the incubation of soil and roots have been widely used together with Δ14C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on: (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, ICBM; (2) if a multiple constraints approach allows determining whether the soil has been storing or losing SOC. To this end ICBM was adapted to model SOC and SO14C in parallel with litterfall and the Δ14C of litterfall as driving variables. The Δ14C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ14C of litterfall. Data from three spruce dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are: (1) the joint use of all 4 observational constraints (SOC stock and its Δ14C, HR flux and its Δ14C) helped to considerably narrow turnover times of the young pool (primarily by Δ14C of HR) and the old pool (primarily by Δ14C of SOC). Furthermore, the joint use all observational constraints allowed constraining the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter estimation yielded the following turnover times (mean ± standard deviation) for SOC in the young pool: Coulissenhieb II 1.7 ± 0.5 yr, Solling D0 5.7 ± 0.7 yr and Howland Tower 1.1 ± 0.5 yr. Turnover times for the old pool were 380 ± 61 yr (Coulissenhieb II), 137 ± 30 yr (Solling D0) and 188 ± 45 yr (Howland Tower), respectively. (2) At all three sites the multiple constraints approach was not able to determine if the soil has been losing or storing carbon. Nevertheless, the relaxed steady state assumption hardly introduced any additional uncertainty for the other parameter estimates. Overall the results suggest that using Δ14C data from more than one carbon pool or flux helps to better constrain SOC models.

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.

Mind the gap: New insights on large-scale forest dynamics over Amazonian forests from airborne lidar and canopy gap data

2021 ◽  
Author(s):  
Ricardo Dalagnol ◽  
Fabien H. Wagner ◽  
Lênio S. Galvão ◽  
Annia S. Streher ◽  
Oliver L. Phillips ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Forest Dynamics ◽  
Tree Mortality ◽  
Temperate Forests ◽  
Brazilian Amazon ◽  
Carbon Stocks ◽  
Airborne Lidar ◽  
Rich Diversity ◽  
Recent Developments ◽  
Multi Temporal

&lt;p&gt;Tree mortality has been pointed out as a key factor to quantify global forests carbon stocks and turnover. While there have been recent developments on observational studies aiming at detection and attribution of tree mortality using remote sensing data in temperate forests, the spatial and temporal distribution of tropical forests mortality is still poorly understood. Tropical forests pose a challenge for mortality detection due to its rich diversity of plant species and heterogeneous canopy structure, which also leads to the occurrence of very frequent and localized mortality events rather than widespread mortality as seen in some temperate forests. Here, we report on recent developments on estimates of spatialized forest dynamics over tropical forests leveraging large datasets of airborne lidar and a newly established link between canopy gaps and canopy mortality. Using multi-temporal lidar datasets collected at five Brazilian Amazon forests with varied forest structure, we linked static gaps, i.e. holes in the forest observed at one date, to dynamic gaps, i.e. gaps that opened from one date to another. Using 610 flight lines of airborne lidar data covering an area &gt;2,300 km&amp;#178; across the Brazilian Amazon, we mapped the static gaps and used them to analyze potential natural and human-induced drivers using generalized linear models. Finally, we produced estimates of annual dynamic gap rates (% yr&lt;sup&gt;-1&lt;/sup&gt;) for the whole Amazon using the combination of the environmental-climate model and the static-dynamic gaps relationship. Our findings show well-defined spatial patterns of dynamic gaps over the Amazon, with 20-35% faster dynamics in the west and southeast than in the central-east and north. Higher gap fractions were more often found at southern and eastern Brazilian Amazon, bordering the &amp;#8216;deforestation arch&amp;#8217;, i.e. regions with increased human influence. Dynamic gaps showed a significant relationship with field mortality rates (R&amp;#178; = 0.40), but with 60% lower magnitude. In fact, what we have detected is very likely mortality with the predominant emphasis of lidar on detecting uprooted and broken mode of death. The analysis also provided new insights on the dynamics of remote areas where we have never visited before. New challenges include testing the gap-method over other sites with multi-temporal data, developing methods to detect standing dead trees, and mapping other drivers such as liana-infested forests. Merging improved regional quantification of dynamic gap estimates with vegetation modelling offers potential to explore how forest dynamics is influencing carbon stocks and turnover, and how they may evolve in the future.&lt;/p&gt;

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 Bayesian calibration of a soil organic carbon model using Δ<sup>14</sup>C measurements of soil organic carbon and heterotrophic respiration as joint constraints

2014 ◽  
Vol 11 (8) ◽  
pp. 2147-2168 ◽  
Author(s):  
B. Ahrens ◽  
M. Reichstein ◽  
W. Borken ◽  
J. Muhr ◽  
S. E. Trumbore ◽  
...  
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Respiration ◽  
Temperate Forests ◽  
Heterotrophic Respiration ◽  
Observational Constraints ◽  
Multiple Constraints ◽  
Bayesian Calibration ◽  
State Assumption

Abstract. Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO2. Soil organic carbon (SOC) turnover has been studied using the Δ14C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ14C values of CO2 that evolved during the incubation of soil and roots have been widely used together with Δ14C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, the Introductory Carbon Balance Model (ICBM); (2) whether relaxing the steady-state assumption in a multiple constraints approach allows the source/sink strength of the soil to be determined while estimating turnover times at the same time. To this end ICBM was adapted to model SOC and SO14C in parallel with litterfall and the Δ14C of litterfall as driving variables. The Δ14C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ14C of litterfall. Data from three spruce-dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are as follows: (1) the joint use of all four observational constraints (SOC stock and its Δ14C, HR flux and its Δ14C) helped to considerably narrow turnover times of the young pool (primarily by Δ14C of HR) and the old pool (primarily by Δ14C of SOC). Furthermore, the joint use of all observational constraints made it possible to constrain the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter estimation yielded the following turnover times (mean ± standard deviation) for SOC in the young pool: Coulissenhieb II 1.1 ± 0.5 years, Solling D0 5.7 ± 0.8 years and Howland Tower 0.8 ± 0.4 years. Turnover times for the old pool were 377 ± 61 years (Coulissenhieb II), 313 ± 66 years (Solling D0) and 184 ± 42 years (Howland Tower), respectively. (2) At all three sites the multiple constraints approach was not able to determine if the soil has been losing or storing carbon. Nevertheless, the relaxed steady-state assumption hardly introduced any additional uncertainty for the other parameter estimates. Overall the results suggest that using Δ14C data from more than one carbon pool or flux helps to better constrain SOC models.

Sign in / Sign up

Export Citation Format

Share Document