scholarly journals REFINEMENT OF CONIFER GROWTH MODELS BASED ON TREE-RING CHRONOLOGIES OF THE NORTH OF WESTERN SIBERIA

2020 ◽  
pp. 41-48
Author(s):  
V. R. Tsibulsky ◽  
I. G. Solovyev ◽  
D. A. Govorkov
Keyword(s):  
Time Series ◽  
Tree Ring ◽  
Growth Model ◽  
Western Siberia ◽  
Growth Function ◽  
Climate Conditions ◽  
The North ◽  
Tree Ring Data ◽  
Model Update ◽  
Pine Trees

The subject of this research is conifer growth model based on time-series of annual rings width. The article addresses processing of data and model update in respect of forest dendrology. The purpose of study is to update the conifer growth model due to expansion of time-series of tree-rings width in regards to conifer forests in Western Siberia. The method represents expansion of time-series due to the fact that some growth phases had not been taken into account. When measurements were taken at the height of 1.3 meters, the following phases were not considered: seedling, juvenile, immature and beginning of virginile phase. The authors carried out examination of a number of scans and core samples, as well as time-series received by other scientists and which are contained in the International Tree-Ring Data Bank. Based on the results of field studies, the authors recommend to add some zeroes to the beginning of time-series within the range of 10-15 years for pine-trees in the south of Western Siberia, depending on growth conditions; the range of 15-30 years in the north for larch-trees and pine-trees depending on soil and climate conditions and latitude. The sequence of data pre-processing operations for time-series, received by means of core sampling, is as follows: averaging out of radius gain in 2 (3) mutually perpendicular directions for one specimen, graphing of radius gain curve, adding to the beginning of time-series, its normalization, approximation by specified growth function. It is possible to build area growth function for the scans. For averaging out a group of model trees, the sequence of operations is as follows: synchronization of time-series by cross-correlation method, approximation by specified growth function. Methods and results of studies can be applied in forest sectors and oil and gas industries for monitoring of forest health conditions. The proposed method of curve growth model update will allow to define more precisely time intervals for efficient forest exploitation as well as to reconstruct digital models of conifer populations in the north of Western Siberia.

scholarly journals Debris-flow activity in abandoned channels of the Manival torrent reconstructed with LiDAR and tree-ring data

2011 ◽  
Vol 11 (5) ◽  
pp. 1247-1257 ◽  
Author(s):  
J. Lopez Saez ◽  
C. Corona ◽  
M. Stoffel ◽  
A. Gotteland ◽  
F. Berger ◽  
...  
Keyword(s):  
Debris Flow ◽  
Tree Ring ◽  
Debris Flows ◽  
Temporal Distribution ◽  
Alluvial Fan ◽  
Tree Ring Data ◽  
Pine Trees ◽  
Spatio Temporal ◽  
Flow Activity ◽  
Abandoned Channels

Abstract. Hydrogeomorphic processes are a major threat in many parts of the Alps, where they periodically damage infrastructure, disrupt transportation corridors or even cause loss of life. Nonetheless, past torrential activity and the analysis of areas affected during particular events remain often imprecise. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris-flow activity in abandoned channels on the forested cone of the Manival torrent (Massif de la Chartreuse, French Prealps). A Light Detecting and Ranging (LiDAR) generated Digital Elevation Model (DEM) was used to identify five abandoned channels and related depositional forms (lobes, lateral levees) in the proximal alluvial fan of the torrent. A total of 156 Scots pine trees (Pinus sylvestris L.) with clear signs of debris flow events was analyzed and growth disturbances (GD) assessed, such as callus tissue, the onset of compression wood or abrupt growth suppression. In total, 375 GD were identified in the tree-ring samples, pointing to 13 debris-flow events for the period 1931–2008. While debris flows appear to be very common at Manival, they have only rarely propagated outside the main channel over the past 80 years. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of four patterns of debris-flow routing and led to the determination of three preferential breakout locations. Finally, the results of this study demonstrate that the temporal distribution of debris flows did not exhibit significant variations since the beginning of the 20th century.

scholarly journals Paleo-hydrologic reconstruction of 400 years of past flows at a weekly time step for major rivers of Western Canada

2019 ◽  
Author(s):  
Andrew R. Slaughter ◽  
Saman Razavi
Keyword(s):  
Time Series ◽  
Water Resources ◽  
Tree Ring ◽  
Flow Distribution ◽  
Future Climate Change ◽  
Western Canada ◽  
Tree Ring Chronology ◽  
Time Step ◽  
Water Resources Systems ◽  
Tree Ring Data

Abstract. The assumption of stationarity in water resources no longer holds, particularly within the context of future climate change. Plausible scenarios of flows that fluctuate outside the envelope of variability of the gauging data are required to assess the robustness of water resources systems to future conditions. This study presents a novel method of generating weekly-time-step flows based on tree-ring chronology data. Specifically, this method addresses two long-standing challenges with paleo-reconstruction: (1) the typically limited predictive power of tree-ring data at the annual and sub-annual scale, and (2) the inflated short-term persistence in tree-ring time series and improper use of prewhitening. Unlike the conventional approach, this method establishes relationships between tree-ring chronologies and naturalised flow at a biennial scale to preserve persistence properties and variability of hydrological time series. Biennial flow reconstructions are further disaggregated to weekly, according to the weekly flow distribution of reference two-year instrumental periods, identified as periods with broadly similar tree-ring properties to that of every two-year paleo-period. The Saskatchewan River Basin (SaskRB), a major river in Western Canada, is selected as a study area, and weekly flows in its four major tributaries are extended back to the year 1600. The study shows that the reconstructed flows properly preserve the statistical properties of the reference flows, particularly, short- to long-term persistence and the structure of variability across time scales. An ensemble approach is presented to represent the uncertainty inherent in the statistical relationships and disaggregation method. The ensemble of reconstructed weekly flows are publically available for download from https://doi.org/10.20383/101.0139 (Slaughter and Razavi, 2019).

Impact of Climate change on tropical terrestrial water use efficiency

2020 ◽  
Author(s):  
Shweta Kumari ◽  
Mark A Adams
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Water Use Efficiency ◽  
Eddy Covariance ◽  
Water Use ◽  
Tree Ring ◽  
Tropical Regions ◽  
The North ◽  
Tree Ring Data ◽  
Use Efficiency

<p>Variability in precipitation and temperature are key markers of climate change. Extreme events like heat waves, droughts, frosts, wind storms, flooding rains and fires greatly affect ecosystem and terrestrial carbon balance. Tropical regions in particular make strong contributions to the global carbon cycle and are the focus of our research. Our initial analysis confirmed the long-known pattern of large variability in rainfall in the tropical southern hemisphere (i.e. between the Tropic of Capricorn and the Equator) w.r.t. the north, with less variation in temperature between the hemispheres. In the follow-up analysis, we focus on exchanges of carbon and water and water use efficiency, based on 39 eddy covariance flux sites which represent 25 years of data across the tropics. Our working hypothesis is that long-term increases in temperature and significant changes (+/-) in rainfall will be reflected in changes in water use efficiency and cropping period, albeit with greater spatial and temporal variation in the south than in the north. We are also investigating relationships between water use efficiency of tropical regions calculated using eddy covariance flux data, with that calculated using tree ring data. We seek to combine methodologies that can help drive our understanding of the impact of climate change on water use efficiency of tropical regions.</p><p><strong><span>Keywords: </span></strong><span>Eddy covariance, Tropics, Water use efficiency, Carbon cycle, Tree ring data</span></p>

scholarly journals Streamflow variability over 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and on geopotential height field reanalysis

2016 ◽  
Author(s):  
P. Brigode ◽  
F. Brissette ◽  
A. Nicault ◽  
L. Perreault ◽  
A. Kuentz ◽  
...  
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Tree Ring ◽  
Tree Rings ◽  
Geopotential Height ◽  
Climatic Reconstruction ◽  
Daily Streamflow ◽  
Tree Ring Data ◽  
Streamflow Variability ◽  
Climatic Time Series

Abstract. Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir to compare the obtained streamflow series and study the natural streamflow variability over the 1881–2011 period. This new reconstruction is based, not on natural proxies, but on a historical reanalysis of global geopotential height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall-runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, both in terms of monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows, and the other one on spring floods. In terms of mean annual flows, the interannual variability of the reconstructed flows were similar (except for the 1930–1940 decade), with significant changes seen in wetter and drier years. For spring floods, the interannual variabilities reconstructed were quite similar for the 1955–2011 period, but significantly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions, and finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

scholarly journals Wavelet analysis of the singular spectral reconstructed time series to study the imprints of Solar–ENSO–Geomagnetic activity on Indian climate

2015 ◽  
Vol 2 (5) ◽  
pp. 1447-1479
Author(s):  
S. Sri Lakshmi ◽  
R. K. Tiwari
Keyword(s):  
Time Series ◽  
Wavelet Analysis ◽  
Time Scales ◽  
Tree Ring ◽  
Geomagnetic Activity ◽  
Temperature Variability ◽  
Temperature Record ◽  
Western Himalayas ◽  
Tree Ring Data ◽  
Reconstructed Time Series

Abstract. In order to study the imprints of solar–ENSO–geomagnetic activity on the Indian Subcontinent, we have applied the Singular Spectral Analysis (SSA) and wavelet analysis to the tree ring temperature variability record from the western Himalayas. The data used in the present study are the Solar Sunspot Number (SSN), Geomagnetic Indices (aa Index), Southern Oscillation Index (SOI) and tree ring temperature record from western Himalayas (WH), for the period of 1876–2000. The SSA and wavelet spectra reveal the presence of 5 years short term ENSO variations to 11 year solar cycle indicating the influence of both the solar–geomagnetic and ENSO imprints in the tree ring data. The presence of 33-year cycle periodicity suggests the Sun-temperature variability probably involving the induced changes in the basic state of the atmosphere. Our wavelet analysis for the SSA reconstructed time series agrees with our previous results and also enhance the amplitude of the signals by removing the noise and showing a strong influence of solar–geomagnetic and ENSO patterns throughout the record. The solar flares are considered to be responsible for cause in the circulation patterns in the atmosphere. The net effect of solar–geomagnetic processes on temperature record thus appears to be the result of counteracting influences on shorter (about 5–6 years) and longer (about 11–12 years) time scales. The present analysis thus suggests that the influence of solar processes on Indian temperature variability operates in part indirectly through ENSO, but on more than one time scale. The analyses hence provides credible evidence for teleconnections of tropical pacific climatic variability with Indian climate ranging from interannual-decadal time scales and also demonstrate the possible role of exogenic triggering in reorganizing the global earth–ocean–atmospheric systems.

scholarly journals Temperature variability at Dürres Maar, Germany during the migration period and at high medieval times, inferred from stable carbon isotopes of Sphagnum cellulose

2011 ◽  
Vol 7 (1) ◽  
pp. 535-573 ◽  
Author(s):  
R. Moschen ◽  
N. Kühl ◽  
S. Peters ◽  
H. Vos ◽  
A. Lücke
Keyword(s):  
Time Series ◽  
Middle Ages ◽  
Tree Ring ◽  
Temperature Variability ◽  
Data Sets ◽  
Stable Carbon ◽  
Migration Period ◽  
Kettle Hole ◽  
Tree Ring Data ◽  
Temperature Reconstructions

Abstract. This paper presents a high resolution reconstruction of local growing season temperature (GST) anomalies at Dürres Maar, Germany, spanning the last two millennia. The GST anomalies were derived from a stable carbon isotope time series of cellulose chemically extracted from Sphagnum leaves (δ13Ccellulose) separated from a kettle-hole peat deposit of several metres thickness. The temperature reconstruction is based on the Sphagnum δ13Ccellulose /temperature dependency observed in calibration studies. Reconstructed GST anomalies show considerable centennial and decadal scale variability. A cold and presumably also wet phase with below-average temperature is reconstructed between the 4th and 7th century AD which is in accordance with the so called European Migration Period marking the transition from the Late Roman Period to the Early Middle Ages. At High Medieval Times above-average temperatures are obvious followed by a temperature decrease. On the contrary, a pronounced Late Roman Climate Optimum, often described as similar warm or even warmer as medieval times, could not be detected. The temperature signal of the Little Ice Age (LIA) is not preserved in Dürres Maar due to considerable peat cutting that takes place in the first half of the 19th century. The local GST anomalies show a remarkable agreement to northern hemispheric temperature reconstructions based on tree-ring data sets and are also in accordance with climate reconstructions on the basis of lake sediments, glacier advances and retreats, and historical data sets. Most notably, e.g. during the Early Middle Ages and at High Medieval Times, temperatures were not low or high in general. Rather high frequency temperature variability with multiple narrow intervals of below- and above-average temperatures at maximum lasting a few decades are reconstructed. Especially the agreements between our estimated GST anomalies and the NH temperature reconstructions derived from tree-ring chronologies indicate the great potential of Sphagnum leaves δ13Ccellulose time series from peat deposits for palaeoclimate research. This is particularly the case, given that a quantitative δ13Ccellulose/temperature relationship has been found for several Sphagnum species. Although the time resolution of Sphagnum δ13Ccellulose data sets certainly wouldn't reach the annual resolution of tree-ring data, reconstructions of past temperature variability on the basis of this proxy hold one particular advantage: due to often relatively high peat accumulation rates, especially in kettle-hole bogs accumulated on temperate latitudes over periods of up to several millennia, they allow extending temperature reconstructions based on tree-ring series into the past to enhance our knowledge of natural climate variability during the Holocene.

scholarly journals Forward modelling of tree-ring width and comparison with a global network of tree-ring chronologies

2013 ◽  
Vol 9 (4) ◽  
pp. 4065-4098 ◽  
Author(s):  
P. Breitenmoser ◽  
S. Brönnimann ◽  
D. Frank
Keyword(s):  
Tree Ring ◽  
Ring Width ◽  
Global Network ◽  
Threshold Temperature ◽  
Tree Ring Width ◽  
Data Set ◽  
Past Climate ◽  
Climate Conditions ◽  
Tree Ring Data ◽  
Wide Range

Abstract. We investigate the relationship between climate and tree-ring data on a global scale using the process-based Vaganov–Shashkin–Lite (VSL) forward model of tree-ring width formation. The VSL model requires as inputs only latitude, monthly mean temperature, and monthly accumulated precipitation. Hence, this simple, process-based model enables ring-width simulation at any location where monthly climate records exist. In this study, we analyse the growth response of simulated tree-rings to monthly climate conditions obtained from the CRU TS3.1 data set back to 1901. Our key aims are (a) to examine the relations between simulated and observed growth at 2287 globally distributed sites and (b) to evaluate the potential of the VSL model to reconstruct past climate. The assessment of the growth-onset threshold temperature of approximately 4–6 °C for most sites and species using a Bayesian estimation approach complements other studies on the lower temperature limits where plant growth may be sustained. Our results suggest that the VSL model skilfully simulates site level tree-ring series in response to climate forcing for a wide range of environmental conditions and species. Spatial aggregation of the tree-ring chronologies to reduce non-climatic noise at the site level yields notable improvements in the coherence between modelled and actual growth. The resulting distinct and coherent patterns of significant relationships between the aggregated and simulated series further demonstrate the VSL model's ability to skilfully capture the climatic signal contained in tree-series. Finally, we propose that the VSL model can be used as an observation operator in data assimilation approaches to reconstruct past climate.

scholarly journals Paleo-hydrologic reconstruction of 400 years of past flows at a weekly time step for major rivers of Western Canada

2020 ◽  
Vol 12 (1) ◽  
pp. 231-243
Author(s):  
Andrew R. Slaughter ◽  
Saman Razavi
Keyword(s):  
Time Series ◽  
Tree Ring ◽  
Flow Distribution ◽  
Future Climate Change ◽  
Western Canada ◽  
Tree Ring Chronology ◽  
Time Step ◽  
Persistence Properties ◽  
Tree Ring Data ◽  
Improper Use

Abstract. The assumption of stationarity in water resources no longer holds, particularly within the context of future climate change. Plausible scenarios of flows that fluctuate outside the envelope of variability of the gauging data are required to assess the robustness of water resource systems to future conditions. This study presents a novel method of generating weekly time step flows based on tree-ring chronology data. Specifically, this method addresses two long-standing challenges with paleo-reconstruction: (i) the typically limited predictive power of tree-ring data at the annual and sub-annual scale and (ii) the inflated short-term persistence in tree-ring time series and improper use of pre-whitening. Unlike the conventional approach, this method establishes relationships between tree-ring chronologies and naturalized flow at a biennial scale to preserve persistence properties and variability of hydrological time series. Biennial flow reconstructions are further disaggregated to weekly flow reconstructions, according to the weekly flow distribution of reference 2-year instrumental periods, identified as periods with broadly similar tree-ring properties to those of every 2-year paleo-period. The Saskatchewan River basin (SaskRB) in Western Canada is selected as a study area, and weekly flows in its four major tributaries are extended back to the year 1600. The study shows that the reconstructed flows properly preserve the statistical properties of the reference flows, particularly in terms of short- to long-term persistence and the structure of variability across timescales. An ensemble approach is presented to represent the uncertainty inherent in the statistical relationships and disaggregation method. The ensemble of reconstructed weekly flows are publicly available for download from https://doi.org/10.20383/101.0139 (Slaughter and Razavi, 2019).

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