Claudia Hartl

Claudia Hartl
Ghent University | UGhent · Department of Environment

Dr. rer. nat.

About

49
Publications
20,581
Reads
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1,044
Citations
Additional affiliations
August 2022 - present
Ghent University
Position
  • Postdoc
April 2022 - June 2022
Justus-Liebig-Universität Gießen
Position
  • Postdoc
June 2021 - September 2021
Independent Researcher
Position
  • Senior Researcher
Education
March 2010 - March 2015
Technische Universität München
Field of study
  • Influence of climate change on mountain forests in the Northern Limestone Alps – a dendroecological approach
October 2003 - November 2009
Universität Regensburg
Field of study
  • Geography

Publications

Publications (49)
Article
Full-text available
Key message Growth response to climate differs between species and elevation. Fir is the most drought-tolerant species. The mountain forests are robust to the climatic changes until now. Abstract Alpine mountain forests provide a wide range of ecological and socio-economic services. Climate change is predicted to challenge these forests, but there...
Article
Full-text available
Mountain forests offer a range of socio-economic and ecological services, e.g. providing wood harvest products, serving as hotspots of biodiversity and fulfilling protective functions. In the European Alps, where these environments are dominated by drought-sensitive Norway spruce, it has been questioned whether these services can be secured in the...
Article
Full-text available
Tree-ring stable isotopes, providing insight into drought-induced eco-physiological mechanisms, are frequently used to reconstruct past changes in growing season temperature and precipitation. Their climatic response is, however, still not fully understood, particularly for data originating from non-extreme, mid-latitude environments with differing...
Article
War has an immediate and obvious effect on people and communities, but its impacts on local ecology can be more subtle. This paper shows how one military encounter in the Second World War has left a clear legacy in the northern forests of Norway, trackable more than seventy years later. We used annual growth rings of ~180 pine and ~30 birch trees a...
Article
The long tradition of dendroclimatological studies in Fennoscandia is fostered by the exceptional longevity and temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world's longest ring width and density-based climate reconstructions have been d...
Article
Tree-ring chronologies encode interannual variability in forest growth rates over long time periods from decades to centuries or even millennia. However, each chronology is a highly localized measurement describing conditions at specific sites where wood samples have been collected. The question whether these local growth variabilites are represent...
Article
Although tree-ring stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes are increasingly used for climate reconstructions, it remains unclear whether isotopic ratios from the two chemical elements and different tree species exhibit age-related trends that require removal prior to any paleoclimatic interpretation. Here, we present 2,355 δ¹³C and 2,237 δ¹...
Article
Full-text available
The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes....
Article
Tree ring-based temperature reconstructions are preferably derived from maximum latewood density (MXD) compared to tree-ring width (TRW). Although temperature signals in MXD are less dependent on site ecology, systematic analyses of the effects of elevation and slope aspect on ring formation are still lacking. Here, we assess the climate sensitivit...
Article
Full-text available
The growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees ( Fagus sylvatica L.) from 324 sites...
Article
Full-text available
Palaeoclimatic evidence is necessary to place the current warming and drying trends of the Mediterranean region in a long-term perspective of pre-industrial variability. Annually resolved and absolutely dated climate proxies that extend back into medieval times are, however, limited to a few sites only. Here we present a network of long ring width...
Article
Full-text available
Maximum latewood density (MXD) measurements from long-lived Black pines (Pinus nigra spp. laricio) growing at the upper treeline in Corsica are one of the few archives to reconstruct southern European summer temperatures at annual resolution back into medieval times. Here, we present a compilation of five MXD chronologies from Corsican pines that c...
Article
Full-text available
Key message Whereas cold temperatures and artificial smoke pollution (during World War II) cause negative pointer years in northern Fennoscandian downy birches, mass outbreaks of Epirrita autumnata L. and Operophtera brumata Bkh. are the strongest growth-influencing and -synchronizing factor. Abstract Variations in radial tree growth of downy birc...
Article
Full-text available
The presence of an ancient, high-elevation pine forest in the Natural Park of Sierras de Cazorla in southern Spain, including some trees reaching >700 years, stimulated efforts to develop high-resolution temperature reconstructions in an otherwise drought-dominated region. Here, we present a reconstruction of spring and fall temperature variability...
Article
Previous work demonstrated the global variability of synchrony in tree growth within populations, that is, the covariance of the year‐to‐year variability in growth of individual neighbouring trees. However, there is a lack of knowledge about the causes of this variability and its trajectories through time. Here, we examine whether climate can expla...
Article
Stable hydrogen isotope ratios of lignin methoxyl groups (δ²HLM) of wood have been shown to reflect climate-sensitive δ²H values of precipitation (δ²Hprecip). However, a detailed calibration study between high-resolution δ²HLM and δ²Hprecip data has not been performed yet. Here, we present annually resolved δ²HLM values from nine tree-ring series (...
Article
Full-text available
X‐ray microdensitometry on annually resolved tree‐ring samples has gained an exceptional position in last‐millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X‐ray based measurement techniques have been the de facto standard. However, studies report...
Article
We analyze annually resolved tree‐ring stable carbon (δ13C) and oxygen (δ18O) isotopic chronologies from Swiss stone pine (Pinus cembra L.) in Romania. The chronologies cover the period between 1876 and 2012 and integrate data from four individual trees from the Calimani Mts in the eastern Carpathians where climatic records are scarce and starts on...
Article
Full-text available
Stable hydrogen isotopes ratios of lignin methoxyl groups (expressed as δ2HLM) of wood have been shown to reflect the climate-sensitive δ2H values of precipitation (expressed as δ2Hprecip) modulated by a large uniform negative isotope fractionation. However, a detailed calibration study among temporal variabilities of δ2HLM in tree-ring series, sit...
Article
Full-text available
Climatically controlled allocation to reproduction is a key mechanism by which climate influences tree growth and may explain lagged correlations between climate and growth. We used continent-wide datasets of tree-ring chronologies and annual reproductive effort in Fagus sylvatica from 1901-2015 to characterise relationships between climate, reprod...
Article
Full-text available
Addressing timely and relevant questions across a multitude of spatiotemporal scales, state-of-the-art interdisciplinary drought research will likely increase in importance under projected climate change. Given the complexity of the various direct and indirect causes and consequences of a drier world, scientific tasks need to be coordinated efficie...
Article
Full-text available
Key message Pinus sylvestris tree-ring δ¹³C and δ¹⁸O records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts. Abstract We produced twentieth century stable isotope data from Pinus sylvestris trees near lakeshores and inland sites in northern Sweden (near Kiruna)...
Article
Spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy-based reconstructions. Here we use tree ring-based temperature reconstructions and state-of-the-art climate model simulations to assess temporal changes in Northern Hemisphere intercontinental temperature covariance duri...
Article
Full-text available
1 Outbreaks of the larch budmoth (LBM) in the European Alps are among the most documented population cycles and their historical occurrence has been reconstructed over 1200 years. 2 Causes and consequences of cyclic LBM outbreaks are poorly understood and little is known about populations near the margin of the host’s distribution range. 3 In the p...
Article
Full-text available
Spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multi-proxy-based reconstructions. Here, we use tree ring-based temperature reconstructions and state-of-the-art climate model simulations to assess temporal changes in Northern Hemisphere inter-continental temperature covariance d...
Article
Full-text available
Information about past volcanic impact on climate is mostly derived from historic documentary data and sulfate depositions in polar ice sheets. Although these archives have provided important insights into the Earth's volcanic eruption history, the climate forcing and exact dating of many events is still vague. Here we apply a new method of break d...
Article
We present the longest high-elevation tree-ring width dataset in the Mediterranean reaching back to the 6th century CE. The network includes 101 living and 92 relict Pinus heldreichii Christ trees from four differently exposed sites in the 2100–2200 m a.s.l. elevation range of Mt. Smolikas in the Pindus Mountains in Greece. Though the sites were al...
Article
Ice core based estimates of past volcanic eruptions are the main forcing of last millennium climate model simulations. Understanding the timing and magnitude of eruptions is thus critical for assessing the dynamics of the Earth’s climate system. Uncertainty associated with a major event in the 1450s, originally attributed to the south Pacific Kuwae...
Article
Full-text available
Norway spruce (Picea abies (L.) Karst.) is an economically significant species of timber industry in Germany. However, previous studies reported a drought sensitivity of spruce questioning the suitability of this species when exposed to future climate change. We analyse the species’ climate sensitivity by comparing high-resolution stem radius chang...
Article
Tree-ring chronologies are widely used to reconstruct high-to low-frequency variations in growing season temperatures over centuries to millennia. The relevance of these timeseries in large-scale climate reconstructions is often determined by the strength of their correlation against instrumental temperature data. However, this single criterion ign...
Article
Full-text available
To study the decay of coarse woody debris (CWD) in forest ecosystems, it is necessary to determine the time elapsed since tree death, which is difficult at advanced decay stages. Here, we compare two methods for age determination of CWD logs, dendrochronological cross-dating and radiocarbon analysis of the outermost tree ring. The methods were comp...
Article
Full-text available
The future performance of native tree species under climate change conditions is frequently discussed, since increasingly severe and more frequent drought events are expected to become a major risk for forest ecosystems. To improve our understanding of the drought tolerance of the three common European temperate forest tree species Norway spruce, s...

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Projects

Projects (2)
Project
A network initiative to link ring-width measurements with satellite-borne earth observations. The TREOS initiative aims to establish a new tree ring research network to explore the possibilities of interpolating tree growth at mesic sites in Central Europe using the latest high-resolution satellite data. In recent decades, satellite imagery has developed rapidly and now provides open access to time series with high temporal and spatial resolution. Earth observations by satellites (EOS) can be related to radial growth of trees if field calibration is performed, which could then support upscaling of tree growth from individual trees to site and landscape levels. Statistical relationships between EOS and tree rings are commonly studied in alpine and boreal forests, where individual growth factors often determine growth. However, at mesic sites in temperate climates, tree growth is limited by multiple factors, and the relationship between EOS and tree growth remains challenging. We hypothesize that at mesic sites, additional site descriptors such as elevation, slope, and forest characteristics play an important role in explaining tree growth. In addition, the application of machine learning algorithms and the use of higher resolution satellite data could increase the predictive accuracy of already established models. However, to train appropriate algorithms, regional to continental tree ring networks covering recent years are needed to allow for a sufficiently large sample size over the entire observation period of the main satellite missions, such as Landsat 8 (since 2013) and Sentinel 2 (since 2015). We therefore invite researchers to participate in our TREOS initiative by sampling and/or providing tree ring data from Central Europe and altitudes below 1200 m that have been collected in October 2018 or a more recent period. Based on the network, we aim to improve our understanding of the robustness and uncertainty of the link between EOS and secondary tree growth of conifers and broadleaves, and to generate appropriate transfer functions.
Project
War has a immediate and obvious effect on people and communities, but its impacts on local ecology can often be more subtle. In this project, researchers from Gutenberg University (Germany) and the University of Minnesota (USA) will explore why one military encounter in the Second World War continues to leave a legacy in the northern forests of Norway more than seventy years later.