Detecting Drought-induced Tree Mortality in Sierra Nevada Forests PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Detecting Drought-induced Tree Mortality in Sierra Nevada Forests PDF full book. Access full book title Detecting Drought-induced Tree Mortality in Sierra Nevada Forests by Sarah Ann Byer. Download full books in PDF and EPUB format.
Author: Sarah Ann Byer
Publisher:
ISBN: 9780355461763
Category :
Languages : en
Pages :
Get Book Here
Book Description
A five-year drought in California has led to a significant increase in tree mortality in the Sierra Nevada forests from 2012 to 2016. Landscape level monitoring of forest health and tree dieback is critical for vegetation and disaster management strategies. We examined the capability of multispectral imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) in detecting and explaining the impacts of the recent severe drought in Sierra Nevada forests. Remote sensing metrics were developed to represent baseline forest health conditions and drought stress using time series of MODIS vegetation indices (VIs) and a water index. We used Random Forest algorithms, trained with forest aerial detection surveys data, to detect tree mortality based on the remote sensing metrics and topographical variables. Map estimates of tree mortality demonstrated that our two-stage Random Forest models were capable of detecting the spatial patterns and severity of tree mortality, with an overall producer’s accuracy of 96.3% for the classification Random Forest (CRF) and a RMSE of 7.19 dead trees per acre for the regression Random Forest (RRF). The overall omission errors of the CRF ranged from 19% for the severe mortality class to 27% for the low mortality class. Interpretations of the models revealed that forests with higher productivity preceding the onset of drought were more vulnerable to drought stress and, consequently, more likely to express tree mortality. This method highlights the importance of incorporating baseline forest health data and measurements of drought stress in understanding forest response to severe drought.
Author: Sarah Ann Byer
Publisher:
ISBN: 9780355461763
Category :
Languages : en
Pages :
Get Book Here
Book Description
A five-year drought in California has led to a significant increase in tree mortality in the Sierra Nevada forests from 2012 to 2016. Landscape level monitoring of forest health and tree dieback is critical for vegetation and disaster management strategies. We examined the capability of multispectral imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) in detecting and explaining the impacts of the recent severe drought in Sierra Nevada forests. Remote sensing metrics were developed to represent baseline forest health conditions and drought stress using time series of MODIS vegetation indices (VIs) and a water index. We used Random Forest algorithms, trained with forest aerial detection surveys data, to detect tree mortality based on the remote sensing metrics and topographical variables. Map estimates of tree mortality demonstrated that our two-stage Random Forest models were capable of detecting the spatial patterns and severity of tree mortality, with an overall producer’s accuracy of 96.3% for the classification Random Forest (CRF) and a RMSE of 7.19 dead trees per acre for the regression Random Forest (RRF). The overall omission errors of the CRF ranged from 19% for the severe mortality class to 27% for the low mortality class. Interpretations of the models revealed that forests with higher productivity preceding the onset of drought were more vulnerable to drought stress and, consequently, more likely to express tree mortality. This method highlights the importance of incorporating baseline forest health data and measurements of drought stress in understanding forest response to severe drought.
Author:
Publisher:
ISBN:
Category : Forest declines
Languages : en
Pages : 0
Get Book Here
Book Description
Climate change is projected to bring more frequent and prolonged droughts, causing widespread forest die-off. Identifying tree mortality over large spatial extents in response to the most recent California drought will help forest managers and conservationists understand where there may be a greater likelihood of future die-offs. In order to find more at-risk areas, this study evaluated how interacting site-specific topographic, climate, substrate, and stand characteristics mediated tree mortality in the Central Sierra Nevada during the 2012-2016 drought. The author used lidar and hyperspectral imagery provided by the National Ecological Observatory Network to identify individual dead trees using the Random Forest classification method and created a Random Forest Regression model to assess site-specific environmental variables that had a greater influence on tree mortality. The results show that the most influential variables were tree height, density, and elevation. Results also found higher mortality rates in pines and oaks, meaning further widespread die-off of these trees could reduce forest productivity, increase fire hazard risk, and drive a shift in community composition over the long-term. This study provides a finer resolution mapping of tree mortality over the research area than was reported by the USFS Aerial Detection Survey. Due to the confounding evidence regarding the relative influence of environmental factors on tree mortality during droughts, these results provide robust information to help maintain these changing forests in a climate-informed manner. Because this study is site-specific, more research is needed to assess how environmental factors mediate drought-induced mortality in other regions also projected to have more intense droughts as a result of climate change.
Author: Chance C. Callahan
Publisher:
ISBN:
Category : Conifers
Languages : en
Pages : 48
Get Book Here
Book Description
Drought-induced tree mortality can drastically alter forest composition, structure, carbon dynamics, and ecosystem function. Increasingly, forest policy and management focuses on how to improve forest resistance and resilience to drought stress. This study used tree ring data at Teakettle Experimental Forest (TEF), a historically frequent fire mixed-conifer forest in the California Sierra Nevada, to quantify how prescribed fire and mechanical thinning conducted in 2001-2002 influenced stand and tree-level growth responses to the extreme California drought of 2012-2016. Overstory thinning and understory thinning significantly enhanced growth responses to treatments alone and treatments during the drought at the stand-level. In each year of the drought, distinct tree species were the only significant predictors of drought resistance at the stand-level. As drought persisted, shade-intolerant pine species yielded greater drought resistance values than shade-tolerant white fir and incense cedar. No prescribed burn effects were found, likely due low fire intensity. At the tree-level, tree diameter (DBH), tree height (HT), crown ratio (CRNR), topographic position index (TPI), and change in growing space over time (competition) were the most important predictors of growth responses to treatments and drought resistance. Mechanical thinning, in both understory and overstory thinning can enhance mixed-conifer forests ability to resist drought by reducing competition and increasing resource availability. This study suggests forest managers have flexibility in prescribing various thinning intensities to promote drought resistance. Prescribed burn effects were not found in this study, but further research is needed to understand long-term burn effects for promoting drought resistance in Sierra Nevada mixed-conifer forests.
Author: James M. Vose
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 302
Get Book Here
Book Description
This assessment provides input to the reauthorized National Integrated Drought Information System (NIDIS) and the National Climate Assessment (NCA), and it establishes the scientific foundation needed to manage for drought resilience and adaptation. Focal areas include drought characterization; drought impacts on forest processes and disturbances such as insect outbreaks and wildfire; and consequences for forest and rangeland values. Drought can be a severe natural disaster with substantial social and economic consequences. Drought becomes most obvious when large-scale changes are observed; however, even moderate drought can have long-lasting impacts on the structure and function of forests and rangelands without these obvious large-scale changes. Large, stand-level impacts of drought are already underway in the West, but all U.S. forests are vulnerable to drought. Drought-associated forest disturbances are expected to increase with climatic change. Management actions can either mitigate or exacerbate the effects of drought. A first principal for increasing resilience and adaptation is to avoid management actions that exacerbate the effects of current or future drought. Options to mitigate drought include altering structural or functional components of vegetation, minimizing drought-mediated disturbance such as wildfire or insect outbreaks, and managing for reliable flow of water.
Author: Sophia Lemmo
Publisher:
ISBN:
Category : Trees
Languages : en
Pages : 0
Get Book Here
Book Description
The 2012-2016 California drought was the most severe in the state’s recorded history, contributing to the death of millions of trees. While the effects of this drought on forests are relatively well studied in the central and southern Sierra Nevada, less is known about its effects on the heavily timbered and diverse forests of northern California. Through sampling 54 0.25 ha plots in northern California, this study compared tree mortality and regeneration patterns before, during, and after California’s most recent record-setting drought. This study evaluated 1) the influence of habitat and competitive covariates on mortality and regeneration trends using ridge regression analysis; and 2) tree death and seedling/sapling establishment dates using dendrochronology and Superposed Epoch Analysis to explore the influence of climate on forest demographics. Montane drought-induced tree mortality occurred primarily in trees smaller than 40 cm diameter at breast height (DBH), with no coastal drought-related mortality in trees with DBH greater than 80 cm. The highest rates of overstory mortality across all sites were observed in Abies grandis (51%), Pinus lambertiana (43%), and Pinus monticola (37%). Picea breweriana (6%) and Picea sitchensis (9%) had the lowest average mortality rates. In montane environments, years with high rates of mortality were positively associated with climatic water deficit (CWD; drier than expected conditions) in the 1-2 years preceding and during tree death dates. Pre-drought montane mortality was greater at wet sites than dry sites, and recent montane mortality (~2013-2020) was positively related with canopy openness. In coastal environments, recent tree mortality was positively associated with maximum temperature and topographic position. Regeneration was dominated by advanced regeneration (median age of 32 years) of shade-tolerant species. In montane environments, regeneration dates were significantly associated with lower-than-average CWD the year proceeding. In coastal environments, regeneration was greater at dry sites than wet sites, and was positively associated with stand density and maximum temperature. These data demonstrate that these forests are not actively perpetuating as diversely into the future, especially in montane environments where more mortality is found in white pine species (Pinus lambertiana and P. monticola) and where the regeneration is weighted towards advanced regeneration of shade-tolerant fir species. This work indicates a need to implement targeted management aimed at generating disturbances to foster balanced and responsive regeneration. This management should preferentially retain medium to larger trees, as these size classes seem to be the least vulnerable to mortality. Such management would be promising for supporting the resilience and diversity of northern California landscapes.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 48
Get Book Here
Book Description
We analyzed gridded daily climate (temperature, precipitation and climatic water deficit) data to identify and characterize the spatiotemporal evolution of the largest Western United States droughts of the last 100 years. Droughts of the last 15 years (2000-2002, 2012-2014) had more extremes of climatic water deficit than earlier droughts, driven by greater temperature and precipitation extremes. Comparing fire extent and severity before, during and after drought events using the Monitoring Trends in Burn Severity dataset (1984-2014), we found fire size and high severity burn extent were greater during droughts than before or after. Similarly, recent Sierra Nevada forest mortality was greatest in drought-affected locations immediately after the drought. Climate simulations anticipate greater extremes in temperature and precipitation in a warming world: droughts and related impacts of the last 15 years may presage the effects of these extremes.
Author: Craig DeLong
Publisher:
ISBN: 9780772680839
Category : Dead trees
Languages : en
Pages : 0
Get Book Here
Book Description
We tested components of a drought mortality decision tool for application in British Columbia forests. The previously estimated drought thresholds for lodge-pole pine and western larch were tested and revised based on the field assessment of visible foliar drought indicators in relation to estimated soil moisture regimes using the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET). Post-processed photography from drones flown over sites with known drought mortality was very successful at mapping dead trees. Using a supervised image classification, dead trees identified in the field were composed of 75% pixels identified as dead. Only 1% of the dead trees were composed of > 50% live pixels based on image classification. In combination, the drought assessment tool using AET/PET estimates, along with image-mapping tools, should be effective at identifying and preparing treatment maps for forests impacted by drought. Furthermore, these tools have the potential to map drought risk, allowing appropriate management planning.
Author: Chad T. Hanson
Publisher: University Press of Kentucky
ISBN: 0813181054
Category : Nature
Languages : en
Pages : 245
Get Book Here
Book Description
Smokescreen cuts through years of misunderstanding and misdirection to make an impassioned, evidence-based argument for a new era of forest management for the sake of the planet and the human race. Natural fires are as essential as sun and rain in fire-adapted forests, but as humans encroach on wild spaces, fear, arrogance, and greed have shaped the way that people view these regenerative events and given rise to misinformation that threatens whole ecosystems as well as humanity's chances of overcoming the climate crisis. Scientist and activist Chad T. Hanson explains how natural alarm over wildfire has been marshaled to advance corporate and political agendas, notably those of the logging industry. He also shows that, in stark contrast to the fear-driven narrative around these events, contemporary research has demonstrated that forests in the United States, North America, and around the world have a significant deficit of fire. Forest fires, including the largest ones, can create extraordinarily important and rich wildlife habitats as long as they are not subjected to postfire logging. Smokescreen confronts the devastating cost of current policies and practices head-on and ultimately offers a hopeful vision and practical suggestions for the future—one in which both communities and the climate are protected and fires are understood as a natural and necessary force.
Author: Angelo Rita
Publisher: Frontiers Media SA
ISBN: 2832510914
Category : Science
Languages : en
Pages : 131
Get Book Here
Book Description
Author: Alisha
Publisher:
ISBN: 9783384262271
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
