scholarly journals TREE-RING FEATURES: INDICATORS OF EXTREME EVENT IMPACTS

IAWA Journal ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 206-231 ◽  
Author(s):  
Achim Bräuning ◽  
Maaike De Ridder ◽  
Nikolay Zafirov ◽  
Ignacio García-González ◽  
Dimitar Petrov Dimitrov ◽  
...  
Keyword(s):  
Tree Ring ◽  
Extreme Events ◽  
Extreme Event ◽  
Reaction Wood ◽  
Anatomical Structures ◽  
Cambial Cell ◽  
Traumatic Resin Ducts ◽  
Earlywood Vessel ◽  
Mechanical Factors ◽  
Flood Rings

Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.

scholarly journals A novel computer-aided tree-ring analysis software (CATS): oak earlywood vessel size reveals a clear spring heat sum response

Trees ◽  
2017 ◽  
Vol 31 (5) ◽  
pp. 1683-1695 ◽  
Author(s):  
Alexander Land ◽  
Matthias Wehr ◽  
Kai-Uwe Roelfs ◽  
Simon Epkes ◽  
Daniel Reichle ◽  
...  
Keyword(s):  
Tree Ring ◽  
Analysis Software ◽  
Tree Ring Analysis ◽  
Vessel Size ◽  
Computer Aided ◽  
Earlywood Vessel ◽  
Ring Analysis

scholarly journals A Comparative Analysis of Climate-Risk and Extreme Event-Related Impacts on Well-Being and Health: Policy Implications

2018 ◽  
Vol 15 (2) ◽  
pp. 331 ◽  
Author(s):  
Walter Leal Filho ◽  
Abul Al-Amin ◽  
Gustavo Nagy ◽  
Ulisses Azeiteiro ◽  
Laura Wiesböck ◽  
...  
Keyword(s):  
Climate Change ◽  
Extreme Events ◽  
Extreme Event ◽  
Well Being ◽  
Lessons Learned ◽  
Policy Implications ◽  
Health Impacts ◽  
Climate Risks ◽  
Wide Range ◽  
Mental Problems

There are various climate risks that are caused or influenced by climate change. They are known to have a wide range of physical, economic, environmental and social impacts. Apart from damages to the physical environment, many climate risks (climate variability, extreme events and climate-related hazards) are associated with a variety of impacts on human well-being, health, and life-supporting systems. These vary from boosting the proliferation of vectors of diseases (e.g., mosquitos), to mental problems triggered by damage to properties and infrastructure. There is a great variety of literature about the strong links between climate change and health, while there is relatively less literature that specifically examines the health impacts of climate risks and extreme events. This paper is an attempt to address this knowledge gap, by compiling eight examples from a set of industrialised and developing countries, where such interactions are described. The policy implications of these phenomena and the lessons learned from the examples provided are summarised. Some suggestions as to how to avert the potential and real health impacts of climate risks are made, hence assisting efforts to adapt to a problem whose impacts affect millions of people around the world. All the examples studied show some degree of vulnerability to climate risks regardless of their socioeconomic status and need to increase resilience against extreme events.

scholarly journals Brief communication "Climatic covariates for the frequency analysis of heavy rainfall in the Mediterranean region"

2011 ◽  
Vol 11 (9) ◽  
pp. 2463-2468 ◽  
Author(s):  
Y. Tramblay ◽  
L. Neppel ◽  
J. Carreau
Keyword(s):  
Extreme Events ◽  
Heavy Rainfall ◽  
Climate Models ◽  
Extreme Event ◽  
Generalized Pareto Distribution ◽  
Climatic Conditions ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
The Future ◽  
Heavy Rainfall Events

Abstract. In Mediterranean regions, climate studies indicate for the future a possible increase in the extreme rainfall events occurrence and intensity. To evaluate the future changes in the extreme event distribution, there is a need to provide non-stationary models taking into account the non-stationarity of climate. In this study, several climatic covariates are tested in a non-stationary peaks-over-threshold modeling approach for heavy rainfall events in Southern France. Results indicate that the introduction of climatic covariates could improve the statistical modeling of extreme events. In the case study, the frequency of southern synoptic circulation patterns is found to improve the occurrence process of extreme events modeled via a Poisson distribution, whereas for the magnitude of the events, the air temperature and sea level pressure appear as valid covariates for the Generalized Pareto distribution scale parameter. Covariates describing the humidity fluxes at monthly and seasonal time scales also provide significant model improvements for the occurrence and the magnitude of heavy rainfall events. With such models including climatic covariates, it becomes possible to asses the risk of extreme events given certain climatic conditions at monthly or seasonal timescales. The future changes in the heavy rainfall distribution can also be evaluated using covariates computed by climate models.

scholarly journals Niche construction mediates climate effects on recovery of tundra heathlands after extreme event

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0245929
Author(s):  
Victoria T. González ◽  
Bente Lindgård ◽  
Rigmor Reiersen ◽  
Snorre B. Hagen ◽  
Kari Anne Bråthen
Keyword(s):  
Extreme Events ◽  
Niche Construction ◽  
Extreme Event ◽  
Recovery Process ◽  
Vegetation Recovery ◽  
Allelopathic Effect ◽  
Climatic Gradient ◽  
Soil Environment ◽  
Ecosystem Recovery ◽  
Continental Climate

Climate change is expected to increase the frequency and intensity of extreme events in northern ecosystems. The outcome of these events across the landscape, might be mediated by species effects, such as niche construction, with likely consequences on vegetation resilience. To test this hypothesis, we simulated an extreme event by removing aboveground vegetation in tundra heathlands dominated by the allelopathic dwarf shrub Empetrum nigrum, a strong niche constructor. We tested the hypothesis under different climate regimes along a 200-km long gradient from oceanic to continental climate in Northern Norway. We studied the vegetation recovery process over ten years along the climatic gradient. The recovery of E. nigrum and subordinate species was low and flattened out after five years at all locations along the climatic gradient, causing low vegetation cover at the end of the study in extreme event plots. Natural seed recruitment was low at all sites, however, the addition of seeds from faster growing species did not promote vegetation recovery. A soil bioassay from 8 years after the vegetation was removed, suggested the allelopathic effect of E. nigrum was still present in the soil environment. Our results provide evidence of how a common niche constructor species can dramatically affect ecosystem recovery along a climatic gradient after extreme events in habitats where it is dominant. By its extremely slow regrowth and it preventing establishment of faster growing species, this study increases our knowledge on the possible outcomes when extreme events harm niche constructors in the tundra.

Analyse dendrochronologique d'un glissement de terrain de la région du Lac à l'Eau Claire (Québec nordique)

1985 ◽  
Vol 22 (2) ◽  
pp. 175-182 ◽  
Author(s):  
Christian Bégin ◽  
Louise Filion
Keyword(s):  
Tree Ring ◽  
Forest Regeneration ◽  
Climatic Conditions ◽  
Reaction Wood ◽  
Growth Rings ◽  
Glissement De Terrain ◽  
Landslide Occurrence ◽  
Slow Progression ◽  
Ring Analysis

A landslide in Clearwater Lake has been dated to spring of 1933 from tree-ring analysis (reaction wood, growth suppression, and corrosion scars). From the 52 sampled trees, seven peak periods of movement were registered within the site before landslide occurrence: 1785, 1815, 1827, 1829, 1852–1853, 1871–1872, 1897, and 1926. After a slow progression lasting 200 years, the slope movements accelerated in 1926, as indicated by suppressed growth rings. It is proposed here that the landslide was the outcome of a long-term slope development partly controlled by climate (precipitation). Postdisturbance forest regeneration (between 1950 and 1976) on the newly exposed substrate is also related to climatic conditions.

Extreme Events Theory and Application

2017 ◽  
pp. 83-115
Keyword(s):  
Extreme Events ◽  
Real World ◽  
Extreme Event ◽  
Investment Strategy ◽  
The Other ◽  
Price Inflation ◽  
Statistical Software ◽  
Tail Risk ◽  
Inflation Risk ◽  
World Markets

In standard statistical methodologies, the probability that the extreme event will occur is very small. But the expected losses in real world markets are higher and sometimes with catastrophic outcomes. Here it seems that the fact that we could lose a certain amount of money 95% or 99% of the time tells us absolutely nothing about what could happen the other 5 or even 1 percent of the time. For that reason, instead of estimating the certain loss, as the standard statistical methodologies account, we introduce a technique known as a “tail risk protecting strategy” or “the barbell investment strategy.” In this chapter, analyzing the copper market movements I understand that the market has been conditioned to believe that the copper demand will exceed its supply. Therefore, I suggest to protect against a growing price-inflation risk. The analyses are conducted using the statistical software STATA 11 and Excel Spreadsheets.

scholarly journals Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

2014 ◽  
Vol 11 (20) ◽  
pp. 5877-5888 ◽  
Author(s):  
D. Zona ◽  
D. A. Lipson ◽  
J. H. Richards ◽  
G. K. Phoenix ◽  
A. K. Liljedahl ◽  
...  
Keyword(s):  
Extreme Events ◽  
Extreme Event ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Co2 Uptake ◽  
Lag Effects ◽  
Tundra Ecosystem ◽  
Co2 Sink ◽  
The Impact

Abstract. The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005–2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

scholarly journals Machine Learning Predictors of Extreme Events Occurring in Complex Dynamical Systems

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 925 ◽  
Author(s):  
Stephen Guth ◽  
Themistoklis P. Sapsis
Keyword(s):  
Time Series ◽  
Extreme Events ◽  
Extreme Event ◽  
Binary Classification ◽  
Selection Criterion ◽  
Area Under The Curve ◽  
Wave Model ◽  
Training Dataset ◽  
Ocean Engineering ◽  
Selection Of

The ability to characterize and predict extreme events is a vital topic in fields ranging from finance to ocean engineering. Typically, the most-extreme events are also the most-rare, and it is this property that makes data collection and direct simulation challenging. We consider the problem of deriving optimal predictors of extremes directly from data characterizing a complex system, by formulating the problem in the context of binary classification. Specifically, we assume that a training dataset consists of: (i) indicator time series specifying on whether or not an extreme event occurs; and (ii) observables time series, which are employed to formulate efficient predictors. We employ and assess standard binary classification criteria for the selection of optimal predictors, such as total and balanced error and area under the curve, in the context of extreme event prediction. For physical systems for which there is sufficient separation between the extreme and regular events, i.e., extremes are distinguishably larger compared with regular events, we prove the existence of optimal extreme event thresholds that lead to efficient predictors. Moreover, motivated by the special character of extreme events, i.e., the very low rate of occurrence, we formulate a new objective function for the selection of predictors. This objective is constructed from the same principles as receiver operating characteristic curves, and exhibits a geometric connection to the regime separation property. We demonstrate the application of the new selection criterion to the advance prediction of intermittent extreme events in two challenging complex systems: the Majda–McLaughlin–Tabak model, a 1D nonlinear, dispersive wave model, and the 2D Kolmogorov flow model, which exhibits extreme dissipation events.

scholarly journals To what extent does variability of historical rainfall series influence extreme event statistics of sewer system surcharge and overflows?

2009 ◽  
Vol 60 (1) ◽  
pp. 87-95 ◽  
Author(s):  
K. Schaarup-Jensen ◽  
M. R. Rasmussen ◽  
S. Thorndahl
Keyword(s):  
Extreme Events ◽  
Extreme Event ◽  
Rain Gauge ◽  
Water Levels ◽  
Rainfall Series ◽  
Rainfall Time Series ◽  
Extreme Statistics ◽  
Maximum Water ◽  
Present Case Study

In urban drainage modelling long term extreme statistics has become an important basis for decision-making e.g. in connection with renovation projects. Therefore it is of great importance to minimize the uncertainties with regards to long term prediction of maximum water levels and combined sewer overflow (CSO) in drainage systems. These uncertainties originate from large uncertainties regarding rainfall inputs, parameters, and assessment of return periods. This paper investigates how the choice of rainfall time series influences the extreme events statistics of max water levels in manholes and CSO volumes. Traditionally, long term rainfall series, from a local rain gauge, are unavailable. In the present case study, however, long and local rain series are available. 2 rainfall gauges have recorded events for approximately 9 years at 2 locations within the catchment. Beside these 2 gauges another 7 gauges are located at a distance of max 20 kilometers from the catchment. All gauges are included in the Danish national rain gauge system which was launched in 1976. The paper describes to what extent the extreme events statistics based on these 9 series diverge from each other and how this diversity can be handled, e.g. by introducing an “averaging procedure” based on the variability within the set of statistics. All simulations are performed by means of the MOUSE LTS model.

Dendrochronological responses to the 24 October 1992 tornado at Sunset Crater, northern Arizona

2005 ◽  
Vol 35 (12) ◽  
pp. 2911-2919 ◽  
Author(s):  
Paul R Sheppard ◽  
Elizabeth M May ◽  
Michael H Ort ◽  
Kirk C Anderson ◽  
Mark D Elson
Keyword(s):  
Tree Ring ◽  
Pinus Ponderosa ◽  
Ring Width ◽  
Reaction Wood ◽  
Release Reaction ◽  
Archaeological Wood ◽  
Northern Arizona ◽  
Growth Changes ◽  
Tornado Damage

This paper documents tree-ring responses to a historic tornado and reevaluates prehistoric tree-ring changes seen in archaeological wood of Wupatki Ruin used to date the 11th-century eruption of Sunset Crater. The historic tornado occurred at Sunset Crater, northern Arizona, on 24 October 1992, and trees within areas damaged by the tornado survived the event and continue living today. The objectives of this research were to document their ring-growth changes and to consider the possibility of tornadoes as a candidate disturbance for the prehistoric ring-growth changes of Wupatki. About half of the trees sampled within areas damaged by the tornado show one or more dendrochronological responses to that event, including ring-width release, reaction wood, ring-width suppression, and (or) reduced latewood. Tornado damage is not a likely candidate for having caused the abrupt ring-width changes at AD 1064–1065 seen at Wupatki. However, five living ponderosa pines (Pinus ponderosa Dougl. ex P. & C. Laws.) at Sunset Crater experienced abrupt and severe suppressions in ring growth beginning decades ago and continuing today. No single disturbance seems obvious for causing these growth suppressions, but further research is merited to find the cause of these modern suppressions to propose a new candidate explanation for the AD 1064 suppression.

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