scholarly journals Partitioning risks of tree mortality by modes of death in managed and unmanaged northern hardwoods and mixedwoods

2017 ◽  
Vol 93 (03) ◽  
pp. 246-258 ◽  
Author(s):  
François Guillemette ◽  
Martin-Michel Gauthier ◽  
Rock Ouimet
Keyword(s):  
Tree Mortality ◽  
Total Mortality ◽  
Tree Level ◽  
Total Risk ◽  
Partial Cutting ◽  
Stem Breakage ◽  
Humus Layer ◽  
Permanent Sample Plot ◽  
Plot Network ◽  
Increasing Precipitation

We used a permanent sample plot network established to monitor the effects of forest management practiced in mature northern hardwood and mixedwood stands in Québec, Canada to address two important questions related to tree mortality: (1) How does partial cutting affect tree mortality? (2) Which variables best explain tree mortality by different modes of death (standing death, uprooting or stem breakage)? Decennial tree deaths were lower after partial cutting than in unharvested plots, but the annual proportion of tree death was similar (1.25%·year-1). At the tree level, a risk-product classification demonstrated the strongest evidence on influencing total mortality, followed by species, the presence of a logging injury, and tree size. Annual temperature was the only climatic variable explaining variations in total risk of tree mortality, and always among the first three variables explaining differences among the three modes of death. The risk of standing death also increased with increasing annual precipitation, while the risk of stem breakage and, to a lesser extent, of being uprooted, decreased with increasing precipitation. Additionally, we found strong evidence to support the effect of the potassium/magnesium ratio of the humus layer on the risk of being uprooted. This information is critical to better understand tree mortality processes.

scholarly journals Mapping Multiple Insect Outbreaks across Large Regions Annually Using Landsat Time Series Data

2020 ◽  
Vol 12 (10) ◽  
pp. 1655 ◽  
Author(s):  
Benjamin C. Bright ◽  
Andrew T. Hudak ◽  
Arjan J.H. Meddens ◽  
Joel M. Egan ◽  
Carl L. Jorgensen
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Tree Mortality ◽  
Landsat Imagery ◽  
Total Mortality ◽  
Google Earth ◽  
Series Data ◽  
Tree Level ◽  
Insect Outbreaks ◽  
Forest Insect

Forest insect outbreaks have caused and will continue to cause extensive tree mortality worldwide, affecting ecosystem services provided by forests. Remote sensing is an effective tool for detecting and mapping tree mortality caused by forest insect outbreaks. In this study, we map insect-caused tree mortality across three coniferous forests in the Western United States for the years 1984 to 2018. First, we mapped mortality at the tree level using field observations and high-resolution multispectral imagery collected in 2010, 2011, and 2018. Using these high-resolution maps of tree mortality as reference images, we then classified moderate-resolution Landsat imagery as disturbed or undisturbed and for disturbed pixels, predicted percent tree mortality with random forest (RF) models. The classification approach and RF models were then applied to time series of Landsat imagery generated with Google Earth Engine (GEE) to create annual maps of percent tree mortality. We separated disturbed from undisturbed forest with overall accuracies of 74% to 80%. Cross-validated RF models explained 61% to 68% of the variation in percent tree mortality within disturbed 30-m pixels. Landsat-derived maps of tree mortality were comparable to vector aerial survey data for a variety of insect agents, in terms of spatial patterns of mortality and annual estimates of total mortality area. However, low-level tree mortality was not always detected. We conclude that our methodology has the potential to generate reasonable estimates of annual tree mortality across large extents.

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.

Pertes d'azote par volatilisation ammoniacale après fertilisation en forêt de pin gris

1971 ◽  
Vol 1 (2) ◽  
pp. 69-79 ◽  
Author(s):  
D. Carrier ◽  
B. Bernier
Keyword(s):  
Ammonium Nitrate ◽  
Ammonia Volatilization ◽  
Urea Hydrolysis ◽  
Soil Horizons ◽  
The Third ◽  
Joint Application ◽  
Humus Layer ◽  
Coated Urea ◽  
Increasing Precipitation ◽  
Underlying Soil

In a field study, percentage of nitrogen lost as ammonia from a jack pine (Pinusbanksiana Lamb.) soil increased with increasing rates of urea application between 112 and 448 kg N/ha. After 7 days, losses amounted to 18–28% of a 224 kg urea-N/ha application, representing 60–87% of the total losses measured over a 6-week period. Maximum volatilization rates occurred between the third and the fifth day after fertilization, at which time urea hydrolysis was virtually complete. Negligible ammonia losses were measured in plots treated with ammonium sulfate, ammonium nitrate, and sulfur-coated urea. Applying superphosphate with urea markedly depressed ammonia volatilization, an effect which was enhanced by a joint application of K2SO4•MgSO4. Reduction of volatilization by artificial precipitation was significant and increased with increasing precipitation when the latter was applied soon after fertilization; decreases in volatilization were then related to the amount of residual urea subject to diffusion into the humus layer or to leaching towards the underlying soil horizons.

scholarly journals Developing a Stand Hazard Index for Oak Decline in Upland Oak Forests of the Ozark Highlands, Missouri

2011 ◽  
Vol 28 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Zhaofei Fan ◽  
Xiuli Fan ◽  
Martin A. Spetich ◽  
Stephen R. Shifley ◽  
W. Keith Moser ◽  
...  
Keyword(s):  
Tree Mortality ◽  
Survival Rates ◽  
Hazard Index ◽  
Classification And Regression Tree ◽  
Tree Level ◽  
Oak Forests ◽  
Oak Decline ◽  
White Oak ◽  
Ozark Highlands ◽  
Black Oak

Abstract Black oak (Quercus velutina Lam.) and scarlet oak (Quercus coccinea Muenchh.)—two major components (44% of total stand basal area) of upland oak forests—are suffering severe decline and mortality in the Ozark Highlands, Missouri. However, factors influencing their survival (mortality) are not well understood. In this study we quantified how stand and tree-level predisposing factors are associated with survival of black and scarlet oaks. Sixteen-year monitoring data from the Missouri Ozark Forest Ecosystem Project (MOFEP) indicated that overall annual mortality of black and scarlet oaks averaged 2.2 and 1.7%, respectively, three to five times higher than expected (around 0.5%) for white oak, a common associate. For the first 8 years of the study (1990‐1998), survival rates of black and scarlet oaks were similar. Thereafter, the survival rate of black oak declined relative to scarlet oak. Using the classification and regression tree (CART) method we classified black oak and scarlet oak trees into seven and nine risk groups, respectively, that differed significantly in rates of tree mortality. Groups were distinguished based on tree diameter, crown class, and size relative to competitors. An oak decline and mortality hazard index was thus developed as the weighted means of risk group mortality, which can help managers prescribe species-specific silvicultural treatments to help mitigate oak decline and associated mortality.

scholarly journals Correlation of Field-Measured and Remotely Sensed Plant Water Status as a Tool to Monitor the Risk of Drought-Induced Forest Decline

Forests ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 77 ◽  
Author(s):  
Daniel Marusig ◽  
Francesco Petruzzellis ◽  
Martina Tomasella ◽  
Rossella Napolitano ◽  
Alfredo Altobelli ◽  
...  
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Forest Decline ◽  
Tree Mortality ◽  
Vegetation Index ◽  
Water Status ◽  
Remotely Sensed ◽  
Plant Water Status ◽  
Tree Level ◽  
Plant Water

Increased frequency of tree mortality and forest decline due to anomalous drought events calls for the adoption of effective monitoring of tree water status over large spatial and temporal scales. We correlated field-measured and remotely sensed plant water status parameters, to test the possibility of monitoring the risk of drought-induced dehydration and hydraulic failure using satellite images calibrated on reliable physiological indicators of tree hydraulics. The study was conducted during summer 2019 in the Karst plateau (NE Italy) in a woodland dominated by Fraxinus ornus L.; Sentinel-2 images were acquired on a seasonal scale on the same dates when absolute water content (AbWC), relative water content (RWC), and minimum water potential (Ψmin) were measured in the field. Plant water status parameters were correlated with normalized difference vegetation index (NDVI and NDVI 8A), normalized difference water index (NDWI), and soil-adjusted vegetation index (SAVI). Significant Pearson and Spearman linear correlations (α < 0.05) emerged between all tree-level measured variables and NDWI, while for NDVI, NDVI 8A, and SAVI no correlation was found. Our results suggest the possibility of using the NDWI as a proxy of tree water content and water potential.

Stem- and stand-level growth and mortality following partial cutting in eastern boreal poplar – white spruce stands

2019 ◽  
Vol 49 (5) ◽  
pp. 463-470 ◽  
Author(s):  
Suzanne Brais ◽  
Brian D. Harvey ◽  
Arun K. Bose
Keyword(s):  
Growth Rates ◽  
Picea Glauca ◽  
Basal Area ◽  
Natural Disturbance ◽  
White Spruce ◽  
Primary Objective ◽  
Post Treatment ◽  
Tree Level ◽  
Growth Responses ◽  
Partial Cutting

Variable retention (VR) and partial cutting are both considered important silvicultural tools of natural disturbance or ecosystem based forest management approaches. Partial harvesting differs from VR in that post-treatment growth responses and stand regeneration are the primary objective rather than the maintenance of biodiversity. This partial cutting study is undertaken in mixed poplar (Populus spp.) – white spruce (Picea glauca (Moench) Voss) stands in the eastern Canadian boreal mixedwood forest. It compares, at the tree level, absolute growth rates (AGR) and relative growth rates (RGR) of basal area (BA) and stem survival; and at the stand level, it also compares absolute BA growth, mortality, and sapling density 10 years following treatment. The completely randomized experiment was established with four intensities of partial cutting (0, 50%, 65%, and 100% of poplar BA). All partial cutting intensities had a significant and similar positive effect on AGR of residual spruce stems. Complete poplar removal resulted not only in the highest increase in RGR of suppressed and intermediate spruce stems, but also in higher spruce mortality. Removal of 50% of the initial poplar stand BA provided the best trade-off between positive residual stem growth of spruce and poplar and limited post-treatment mortality.

scholarly journals Tree mortality in a riparian forest at Rio Paraguai, Pantanal, Brazil, after an extreme flooding

2004 ◽  
Vol 18 (4) ◽  
pp. 839-846 ◽  
Author(s):  
Geraldo Alves Damasceno-Junior ◽  
João Semir ◽  
Flavio Antonio Maës dos Santos ◽  
Hermógenes de Freitas Leitão-Filho
Keyword(s):  
Mortality Rate ◽  
Tree Mortality ◽  
Riparian Forest ◽  
Total Mortality ◽  
Community Level ◽  
Extreme Floods ◽  
Diameter At Breast Height ◽  
Breast Height ◽  
Extreme Flooding ◽  
Topographic Positions

A study was conducted in a riparian forest (Rio Paraguai, Brazil) to verify the vegetation mortality after an exceptional flooding in 1995. Individuals with diameter at breast height > 5 cm were sampled in 108 (10×10m) plots in 1994, and re-sampled in 1996. The total mortality rate was 4.1% per year. The mortality increased with the increasing of topographic positions, at community level, suggesting that places where the flooding is less frequent are more affected by extreme floods.

Long-term trends in tree mortality rates in the Alberta foothills are driven by stand development

2012 ◽  
Vol 42 (9) ◽  
pp. 1687-1696 ◽  
Author(s):  
H.C. Thorpe ◽  
L.D. Daniels
Keyword(s):  
Mortality Risk ◽  
Forest Structure ◽  
Tree Mortality ◽  
Mortality Rates ◽  
Tree Level ◽  
Model Parameters ◽  
Stem Density ◽  
Stand Development ◽  
Individual Tree ◽  
Local Competition

Tree mortality is a critical driver of stand dynamics, influencing forest structure, composition, and capacity for ecosystem service provision. In recent years, tree mortality has been gaining attention as dramatic occurrences of forest die-off have been linked to climate change. Using permanent sample plot data, we examined tree mortality rates in mature forests in west-central Alberta from 1956 to 2007. We quantified mortality risk at an individual-tree level as a function of size, local competition, and calendar year, a proxy for increasing temperature, and used maximum likelihood methods to estimate species-specific model parameters. Tree size and local competition were both important predictors of mortality risk. However, once these factors were included in our model, no additional variation could be attributed to calendar year, indicating that the trend of increasing tree mortality over time found in our raw data is primarily a result of stand development processes. This finding is supported by the changes in forest structure and composition that we documented over the study period. Stands generally increased in basal area and stem density, and lodgepole pine ( Pinus contorta var. latifolia Engelm. ex S. Watson) declined in abundance relative to the more shade-tolerant black spruce ( Picea mariana (Mill.) B.S.P.) and white spruce ( Picea glauca (Moench) Voss). Our results indicate that warming-related changes did not affect background tree mortality rates in mature forests in the Alberta foothills over the study period. These results also provide critical information for future studies of forest dynamics in the region.

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