Network Of Chronologies Research Articles

Reconstructed Late Summer Maximum Temperatures for the Southeastern United States From Tree‐Ring Blue Intensity

AbstractOver recent decades, the southeastern United States (Southeast) has become increasingly well represented by the terrestrial climate proxy record. However, while the paleo proxy records capture the region's hydroclimatic history over the last several centuries, the understanding of near surface air temperature variability is confined to the comparatively shorter observational period (1895‐present). Here, we detail the application of blue intensity (BI) methods on a network of tree‐ring collections and examine their utility for producing robust paleotemperature estimates. Results indicate that maximum latewood BI (LWBI) chronologies exhibit positive and temporally stable correlations (r = 0.28–0.54, p < 0.01) with summer maximum temperatures. As such, we use a network of LWBI chronologies to reconstruct August‐September average maximum temperatures for the Southeast spanning the period 1760–2010 CE. Our work demonstrates the utility of applying novel dendrochronological techniques to improve the understanding of the multi‐centennial temperature history of the Southeast.

Hydrological Variability in the El Cielo Biosphere Reserve, Mexico: A Watershed-Scale Analysis Using Tree-Ring Records

The El Cielo Biosphere Reserve (CBR) stands as a vital forested region in eastern Mexico due to its high biodiversity in flora and fauna and provision of environmental services. This study established a network of 10 ring-width chronologies of different species within the CBR and adjacent watersheds. The objective was to analyze their climatic response and reconstruct the seasonal streamflow contribution of each sub-basin to the main stream, utilizing data from a gauge network of eight hydrological stations located at strategic locations of the CBR. With chronologies ranging from 116 to 564 years, most exhibited association with the accumulated streamflow between January and June. Based on the adjusted R2, Akaike Information Criteria, and Variance Inflation Factor, the stepwise regression procedure was selected among different statistical methods for developing the reconstruction model. In spite of differences in the seasonal reconstructed periods, all the species showed potential to develop hydrological reconstructions as indicated by their common response to streamflow variability, as occurred in the wet years of 1976, 1993, 2000, and 2008, and dry years of 1980, 1982, 1996, and 2011. It was found that the response of the chronologies to gauge records increased as a function of the chronologies’ interseries correlation, average mean sensitivity, and distance of the tree-ring series to the gauge station. Streamflow reconstructions at the sub-basin level allowed a better understanding of the hydroclimatic variability characterizing the CBR, but also suggested the need to increase the network of chronologies for some particular sub-basins lacking tree-ring series to improve the reconstructed models.

Runoff Variability in the Truckee–Carson River Basin from Tree Rings and a Water Balance Model

Abstract Regional warming and associated changes in hydrologic systems pose challenges to water supply management in river basins of the western United States and call for improved understanding of the spatial and temporal variability of runoff. We apply a network of total width, subannual width, and delta blue intensity tree-ring chronologies in combination with a monthly water balance model to identify droughts and their associated precipitation P and temperature T footprints in the Truckee–Carson River basin (TCRB). Stepwise regression gave reasonably accurate reconstructions, from 1688 to 1999, of seasonal P and T (e.g., R2 = 0.50 for May–September T). These were disaggregated to monthly values, which were then routed through a water balance model to generate “indirectly” reconstructed runoff. Reconstructed and observed annual runoff correlate highly (r = 0.80) from 1906 to 1999. The extended runoff record shows that twentieth-century droughts are unmatched in severity in a 300-yr context. Our water balance modeling reconstruction advances the conventional regression-based dendrochronological methods as it allows for multiple hydrologic components (evapotranspiration, snowmelt, etc.) to be evaluated. We found that imposed warming (3° and 6°C) generally exacerbated the runoff deficits in past droughts but that impact could be lessened and sometimes even reversed in some years by compensating factors, including changes in snow regime. Our results underscore the value of combining multiproxy tree-ring data with water balance modeling to place past hydrologic droughts in the context of climate change. Significance Statement We show how water balance modeling in combination with tree-ring data helps place modern droughts in the context of the past few centuries and a warming climate. Seasonal precipitation and temperature were reconstructed from multiproxy tree-ring data for a mountainous location near Lake Tahoe, and these reconstructions were routed through a water balance model to get a record of monthly runoff, snowmelt, and other water balance variables from 1688 to 1999. The resulting extended annual runoff record highlights the unmatched severity of twentieth-century droughts. A warming of 3°C imposed on reconstructed temperature generally exacerbates the runoff anomalies in past droughts, but this effect is sometimes offset by warming-related changes in the snow regime.

Interspecific differences in drought and pluvial responses for Quercus alba and Quercus rubra across the eastern United States

Quercus is one of the most important genera of plants in North America, but is currently undergoing a decrease in abundance and dominance of North American forest ecosystems. Of the two most common North American Quercus species, eastern white oak (Quercus alba) has experienced a slightly greater decline in dominance compared to northern red oak (Quercus rubra). Changes in Quercus demographics are likely due to multiple factors, but also highlight the importance of understanding the growth-climate relationships of these species under shifting climatic regimes. Therefore, we developed a network of tree-ring chronologies and stomatal conductance measurements where Q. alba and Q. rubra co-occur that spans the longitudinal extent of both species’ geographic ranges. We compared growth reductions due to drought conditions, and growth increases due to pluvial conditions, of both species. The drought response (by reductions in radial growth and stomatal conductance) of Q. alba was consistently greater than Q. rubra irrespective of temporal or spatial drought dynamics. Similarly, the pluvial response (relative increase in growth) of Q. alba was greater than Q. rubra. We also found that both species exhibit nonlinear relationships to water availability, where increases in growth during pluvial conditions are less than the decreases in growth due to drought conditions. Thus, we concluded that Q. alba is moderately more sensitive to water availability than Q. rubra, which provides new insight for Quercus isohydricity classification, and may indicate different sensitivities to a changing precipitation regime in North America.

Uncovering the spatiotemporal patterns of traffic congestion from large-scale trajectory data: A complex network approach

Understanding the spatiotemporal characteristics of traffic congestion is the cornerstone of generating traffic management and control strategies. Based on the large-scale taxi trajectory data in Shenzhen, China, this study designs an effective framework to explore the spatiotemporal patterns of traffic congestions. To bridge trajectory data with urban road networks, we develop a two-stage map-matching method from the aspects of distance and angle. Then, the free-flow speed of each road segment is extracted and employed to identify traffic congestion. In this way, a novel complex network method, named chronological network (chronnet), is utilized for traffic congestion modeling, and we employ an overlapping community detection algorithm to identify region-level bottlenecks. According to the network properties, we explore the influence scope of traffic congestions and uncover the role of each road segment in the propagation process. Meanwhile, community detection results indicate that there are typical local clustering structures in traffic congestions, and each community also has its unique traffic characteristics. Overall, these findings reveal that the complex network can effectively mine the consecutive patterns of traffic congestion.

Streamflow reconstructions from tree rings and variability in drought and surface water supply for the Milk and St. Mary River basins

The Milk and St. Mary Rivers are international waterways straddling the United States and Canada and traversing four Tribal Nations before draining into the Missouri and South Saskatchewan Rivers respectively. Management of water resources in the region is challenged by the complexity of stakeholder interests, the limitations of existing management infrastructure, and by a limited characterization of the long-term streamflow and hydroclimatic variability across the area. We used existing records of natural streamflow to investigate the relationships between seasonal climate variability and differences in the timing and volume of flow from the headwaters to the prairie tributaries. Then, using a network of tree-ring chronologies to reconstruct records of past streamflow, we assessed whether drought risk relates to these sub-basin specific differences and if drought events experienced during the observational period are representative of those that have occurred over the long-term. Observed climate-flow relationships suggest that outside of the mountain headwaters, where precipitation dominates the hydrograph, streamflow variability on lower reaches of the Milk River is particularly sensitive to winter temperatures. This sensitivity was reflected by severe drought conditions over the prairies during the 2000s, implying potentially large future flow reductions with warming. The streamflow reconstructions show sub-basin specific drought risks that also imply greater temperature driven drought severities across the prairie tributaries. Within the mountain and foothill sub-basins numerous past drought episodes exceed the magnitude and duration of observational period events, which implies the potential for future water supply management challenges stemming from severe, long-duration droughts coupled with the negative hydrologic effects of warmer temperatures.

Centennial Scots pine chronologies for western, central and eastern Lithuania

Although two centennial Scots pine chronologies for the dating of timber in Lithuania were constructed in the 2000 s, the Baltic countries still lack a network of regional chronologies. To fill this gap, we constructed three Scots pine chronologies for western, central and eastern Lithuania. Here we present chronologies covering the fifteen to the twentieth centuries. Our analysis revealed a strong teleconnection of the compiled chronologies with Scots pine chronologies constructed in Poland, Latvia, Estonia, and Belarus. The established link with Belarus chronologies and the fact that some of the timber in Lithuanian buildings could be of Belarus origin is important in the long-distance timber trade during the last 500 years. Dendroclimatological analysis has shown that constructed tree-ring chronologies are sensitive to air temperatures in February and March. Therefore, the constructed chronologies have a potential for climate reconstructions and dendroprovenancing.

Intra-annual ring width and climate response of red pine in Itasca State Park in north-central Minnesota

Red pine (Pinus resinosa Ait.) of northern Minnesota are part of a growing network of tree-ring chronologies aimed at understanding climate dynamics in the Upper Great Lakes Region. Red pine has been widely used in tree-ring studies of fire and climate variability across its range. Earlier studies have relied primarily on total annual ring width. Here we develop annual and subannual (i.e., earlywood, latewood, and adjusted latewood) chronologies from Itasca State Park to refine our understanding of red pine climate response. Our chronologies extend to the early 18th century and display common growth and cross-dating characteristics indicative of a significant common controlling mechanism. We found that total ring width contains dampened attributes reflective of both the temperature-limited earlywood and moisture-dependent latewood chronologies. The strongest relationship between climate and radial growth is between the adjusted latewood chronology and 3-month summer precipitation, suggesting that overall summer wetness rather than any single summer month primarily limits growth. The ability to disaggregate and improve upon the mixed climate signal of red pine highlights the potential of using intra-annual chronologies to strengthen future climate reconstructions. We hope the methodologies demonstrated here serve as a potential guide for future red pine chronology development in the region.

The First Network of Tree-Ring Chronologies for Co-Occurring Nothofagus nervosa and Nothofagus obliqua along a Precipitation Gradient in Patagonia, Argentina

We present the first network of tree-ring chronologies for co-occurring Nothofagus nervosa and Nothofagus obliqua in Argentina. Using standard dendrochronological techniques, we developed seven tree-ring width chronologies for each species, encompassing their E-W distribution along a precipitation gradient. Chronology statistics indicated that N. nervosa and N. obliqua are strong candidates for research in dendrochronology. The chronologies were used to study and compare the temporal and spatial growth patterns of each species. Correlation and principal components analysis of the tree-ring chronologies serve as evidence of a strong common signal, indicating shared regional growth patterns across the gradient with some exceptions between sites and species. These results indicate the high potential of N. nervosa and N. obliqua for their use in dendroclimatology.

The dendrochronological proof of origin of oak churches located in the Czech Republic

Transcarpathian wooden churches started to dilapidate after World War I. To preserve the architectural heritage, five oak churches were transported from the region to the territory of today's Czech Republic. However, an exact date of their construction and origin of wood have not been specified and evidenced in literature. In this study, 63 samples have been collected and processed using standard dendrochronological methods. Three Baroque churches, coming from the Mukachevo district, were absolutely dated thanks to the preserved waney edge or sapwood tree rings to periods 1734–1744, 1753–1755, and 1783–1795. Two other churches, representing Gothic architecture, were transported from a more eastern part of Transcarpathian Ukraine. One of them was dated to the period after 1655 and the other could not be reliably dated using available reference chronologies. The created mean tree-ring width series representing individual churches showed strong correlations with the reference chronologies for Slovakia and northern Romania whereas correlations with the only Ukrainian chronology (Lviv region) were negligible. This could suggest low Transcarpathian tree-ring coherency and may indicate the need to create a dense network of regional tree-ring width chronologies in the regions surrounding the Carpathian Mountains.

The four smarts of Industry 4.0: Evolution of ten years of research and future perspectives

The Industry 4.0 literature has exponentially grown in the past decade. We aim to understand how this literature has evolved and propose future research opportunities. We focus on four smart dimensions of Industry 4.0: Smart Manufacturing, Smart Products and Services, Smart Supply Chain, and Smart Working. We perform a machine learning-based systematic literature review. Our analysis included 4,973 papers published from 2011 to 2020. We conducted a chronological network analysis considering the growth of these four dimensions and the connections between them. We also analyzed keywords and the main journals publishing on these four smart dimensions. We show that the literature has mainly been devoted to the study of Smart Manufacturing, although attention to the other smart dimensions has been growing in recent years. Smart Working is the less explored dimension, with many opportunities for future research. We show that research opportunities are concentrated in the interfaces between the different smart dimensions. Our findings support the vision of Industry 4.0 as a concept transcending the Smart Manufacturing field, thus creating opportunities for synergies with other related fields. Scholars can use our findings to understand the orientation of journals and gaps that can be fulfilled by future research.

Application of Multilayer Network Models in Bioinformatics.

Multilayer networks provide an efficient tool for studying complex systems, and with current, dramatic development of bioinformatics tools and accumulation of data, researchers have applied network concepts to all aspects of research problems in the field of biology. Addressing the combination of multilayer networks and bioinformatics, through summarizing the applications of multilayer network models in bioinformatics, this review classifies applications and presents a summary of the latest results. Among them, we classify the applications of multilayer networks according to the object of study. Furthermore, because of the systemic nature of biology, we classify the subjects into several hierarchical categories, such as cells, tissues, organs, and groups, according to the hierarchical nature of biological composition. On the basis of the complexity of biological systems, we selected brain research for a detailed explanation. We describe the application of multilayer networks and chronological networks in brain research to demonstrate the primary ideas associated with the application of multilayer networks in biological studies. Finally, we mention a quality assessment method focusing on multilayer and single-layer networks as an evaluation method emphasizing network studies.

A multimillennial snow water equivalent reconstruction from giant sequoia tree rings

The first dendroclimatic reconstruction of May 1 snow water equivalent (SWE) was developed from a Sequoiadendron giganteum regional tree-ring chronology network of 23 sites in central California for the period 90–2012 CE. The reconstruction is based on a significant relationship between May 1 SWE and tree-ring growth and shows climate variability from interannual to intercentennial time scales. A regression-based reconstruction equation explains up to 55% of the variance of SWE for 1940–2012. Split-sample validation supports our use of a reconstruction model based on the full period of reliable observational data (1940–2012). Thresholds for May 1 SWE low (15 percentile) and high (80 percentile) years were selected based on the exploratory scatterplots relationship between observed and reconstructed data for the period 1940–2012. The longest period of consecutive low-SWE years in the reconstruction is 2 years and the frequency of the lowest SWE years is highest during the period 710–809 CE. The longest high-SWE period, defined by consecutive wet years, is 3 years (558–560 CE). SWE and its reconstruction positively correlate with northeastern Pacific sea surface temperatures, the low-frequency variability of which may provide some predictive ability. Ultimately, the instrumental record and reconstruction suggest that unlike other sites in the region, twentieth century SWE variability in these Sequoia groves has remained within historical boundaries and relatively buffered from extremes and severe declines, though this is likely to change in coming decades with potentially negative effects on water availability for these trees.

Increasing climate sensitivity of subtropical conifers along an aridity gradient

Subtropical forests are an important but still poorly understood component of the global carbon cycle and global biodiversity. If climate continues to change as anticipated, increasing drought may affect the composition and structure of many subtropical forests. Understanding the environmental conditions that determine drought sensitivity across subtropical ecosystems and trees species will help accurately predict their response to climate change and inform the best mitigation and protection strategies. To identify the broad-scale drivers of drought sensitivity, we collected a large network of ring-width chronologies along a broad climate gradient that spans from east to west of the Yunnan-Guizhou Plateau (YGP), in southwestern China. Our network includes growth data from 10 trees species in 28 old growth subtropical coniferous sites. We used tree ring analyses, Redundancy Analysis (RDA), and linear mixed effects models to assess how drought responses varied geographically, climatically, and taxonomically. We found that aridity exerted the strongest limitation in our study area, implying that subtropical forest responses to drought may be more complex than commonly assumed. Moreover, we found that drought intensity during dry season, proxied by aridity index, is a stronger driver of drought sensitivity than stand characteristics and microenvironment. Further increases in drought frequency and dry season drought intensity in the region associated with climate change may pose a larger-than-expected threat to the growth, and ultimately persistence, of many subtropical coniferous forests.

Chronological networks in archaeology: A formalised scheme

This paper proposes a new methodology for modelling chronological data in archaeology. We introduce the concept of “chronological network”, a flexible model for representing chronological entities, synchronisms between them, and other chronological constraints such as termini post/ante quem and duration bounds. We propose a procedure for checking the consistency of a chronological network and for refining dating estimates from the available synchronisms and constraints. We introduce ChronoLog, a chronology software application that allows users to build a chronological network interactively. The software automatically checks the consistency of the network and computes the tightest possible chronological range for each entity, within seconds. ChronoLog is freely available online at http://chrono.ulb.be.

Sampling density and date along with species selection influence spatial representation of tree-ring reconstructions

Abstract. Our understanding of the natural variability of hydroclimate before the instrumental period (ca. 1900 CE in the United States) is largely dependent on tree-ring-based reconstructions. Large-scale soil moisture reconstructions from a network of tree-ring chronologies have greatly improved our understanding of the spatial and temporal variability in hydroclimate conditions, particularly extremes of both drought and pluvial (wet) events. However, certain regions within these large-scale network reconstructions in the US are modeled by few tree-ring chronologies. Further, many of the chronologies currently publicly available on the International Tree-Ring Data Bank (ITRDB) were collected in the 1980s and 1990s, and thus our understanding of the sensitivity of radial growth to soil moisture in the US is based on a period that experienced multiple extremely severe droughts and neglects the impacts of recent, rapid global change. In this study, we expanded the tree-ring network of the Ohio River valley in the US, a region with sparse coverage. We used a total of 72 chronologies across 15 species to examine how increasing the density of the tree-ring network influences the representation of reconstructing the Palmer Meteorological Drought Index (PMDI). Further, we tested how the sampling date and therefore the calibration period influenced the reconstruction models by creating reconstructions that ended in the year 1980 and compared them to reconstructions ending in 2010 from the same chronologies. We found that increasing the density of the tree-ring network resulted in reconstructed values that better matched the spatial variability of instrumentally recorded droughts and, to a lesser extent, pluvials. By extending the calibration period to 2010 compared to 1980, the sensitivity of tree rings to PMDI decreased in the southern portion of our region where severe drought conditions have been absent over recent decades. We emphasize the need of building a high-density tree-ring network to better represent the spatial variability of past droughts and pluvials. Further, chronologies on the ITRDB need updating regularly to better understand how the sensitivity of tree rings to climate may vary through time.

The Driftless Oaks: A new network of tree-ring chronologies to improve regional perspectives of drought in the Upper Midwest, USA

New and updated multi-century tree-ring chronologies from living oak trees, remnants, and archeological beams from across the Driftless Area of southwest Wisconsin and northeast Iowa, USA, were developed to fill a spatial gap in the network of available tree-ring chronologies. We produced a robust 303-year summer drought reconstruction (June–August Palmer’s Modified Drought Index (PMDI): r 2 = 0.45) that identified clusters of extreme droughts and pluvials (PMDI ≤ –4.0 or ≥ 4.0) in the early 1700s and more even distributions of drought conditions, with the exception of the post 1930s period when drought became relatively infrequent. Compared to the Living Blended Drought Atlas (LBDA) and the North American Drought Atlas (NADA), our reconstruction more accurately represented moderate moisture conditions across the Driftless Area, the NADA and LBDA more closely represented extreme pluvials, and our reconstruction and the LBDA better represented extreme drought years. The three reconstructions largely captured the same high-frequency variability in drought conditions and differed most at low frequencies. Significant correlations were identified between our reconstruction and corn ( r = 0.30, n = 91, p = 0.002) and soybean ( r = 0.25, n = 81, p = 0.012) yields, with the strength of the correlations increasing over recent decades suggesting a tighter coupling of interannual climate variability and crop productivity in the region. Superposed epoch analyses indicated significantly wetter conditions in the Driftless Area two years after major volcanic eruptions. In the context of long-term climatic variability, the Driftless Oaks drought reconstruction demonstrated that drought and pluvial conditions more extreme than those experienced during the instrumental record have occurred in the past.

Climate and atmospheric circulation related to frost-ring formation in Picea mariana trees from the Boreal Plains, interior North America

Earlier spring and earlier onset of growth, as a consequence of climate change, may expose trees and crops to increased risk of exposure to frost damage. In this study, we compare the frequency of frost rings in three regions [Porcupine Provincial Forest (PPF; north-latitude); Duck Mountain Provincial Forest (DMPF; mid-latitude) and Riding Mountain National Park (RMNP, south-latitude)] located in the Boreal Plains of interior North America. In each of PPF and DMPF, twenty upland black spruce [Picea mariana (Mill.) BSP] trees were sampled using stem analysis and others were sampled at breast height or below. In RMNP, multiple coniferous tree species were sampled at breast height or below to allow comparison among species. Results from stem analysis indicated that frost rings were more frequent in DMPF than PPF (north of DMPF). Frost rings identified up to a height of 16 m and were formed predominantly in the early cambial age zone. As a general pattern, frost rings recorded in PPF occurred more abundantly in years with warm April temperatures and this association was less prevalent in DMPF. Frost rings were formed following extreme frost events in late May - early June and frost-ring years corresponded to years with cooler June temperatures. A significant positive association was found between frost-ring frequency and the El Niño Southern Oscillation. In the absence of an early spring, black spruce trees were less affected by frost damages. Stem analysis provided a better record of spring frosts than solely sampling at breast height or below. The multi-species approach used in RMNP revealed many years with synchronous frost rings among species. The development of a large network of frost-ring chronologies from tree species of various age classes and/or from stem analysis will help with assessing the impact of late spring frosts on forest dynamics and to document large-scale climate anomalies in areas with low climate data coverage and/or prior to instrumental records.

The European Russia Drought Atlas (1400–2016 CE)

We present the European Russia Drought Atlas (ERDA) that covers the East European Plain to the Ural Mountains from 1400–2016 CE. Like the Old World Drought Atlas (OWDA) for the Euro-Mediterranean region, the ERDA is a one-half degree gridded reconstruction of summer Palmer Drought Severity Indices estimated from a network of annual tree-ring chronologies. Ensemble point-by-point regression is used to generate the ERDA with the identical protocols used for developing the OWDA. Split calibration/validation tests of the ERDA indicate that it has significant skill over most of its domain and is much more skillful than the OWDA where they overlap in the western part of ERDA domain. Comparisons to historical droughts over European Russia additionally support the ERDA’s overall validity. The ERDA has been spatially smoothed and infilled using a local regression method to yield a spatially complete drought atlas back to 1400 CE. EOF analysis indicates that there are three principal modes of hydroclimatic variability in the ERDA. After Varimax rotation, these modes correlate significantly with independent climate data sets extending back to the late nineteenth century in a physically interpretable way and relate to atmospheric circulation dynamics of droughts and heatwaves over European Russia based on more recent instrumental data.

A network of bivalve chronologies from semi-enclosed seas

Four chronologies of the bivalve species Glycymeris pilosa have been constructed along a 300 km gradient of the eastern coastal Adriatic Sea, all of which span the common period of 1982–2015. The chronologies are compared to local and remote environmental drivers suspected to influence the biology of the system, including air and seawater temperature, precipitation and freshwater discharge. The Adriatic-Ionian Bimodal Oscillating System (BiOS), a key oceanographic feature quantified by satellite-derived absolute dynamic topography, is also compared to the chronologies. The chronologies at the two southern sites are more strongly influenced by local river discharge, while the two northern chronologies are more strongly influenced by BiOS. These results highlight the broadscale importance of BiOS to the Adriatic system as well as the heterogeneity of nearshore environmental and drivers of growth. These G. pilosa chronologies provide unique multidecadal, continuous, biological time series to better understand the ecology and fine-scale variability of the Adriatic with potential for other shallow, semi-enclosed seas.