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Rolf Theodor Walter Siegwolf

Rolf Theodor Walter Siegwolf

PhD

About

337
Publications
68,982
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Introduction
As a plant ecophysiologist I use stable isotopes to study the response of plants to environmental impacts. I am particularly interested in the effects of environmental changes on C, H2O fluxes and growth patterns. The variations of stable isotope ratios as a sensitive tool are instrumental in the investigation of plant responses to environmental changes. All the more I am interested in isotopic fractionations, their drivers and mechanisms in plant metabolic processes, also during my retirement.
Additional affiliations
January 2017 - present
Swiss Federal Institute for Forest, Snow and Landscape Research WSL
Position
  • Researcher
Description
  • As a guest researcher I have the opportunity to participate in various projects experimentally and as a consultant in my fields of interest and expertise.
January 2012 - July 2016
ETH Zurich
Position
  • Ecophysiology in Agricultural Sciences
January 2010 - July 2014
University of Basel
Position
  • Lecturer

Publications

Publications (337)
Book
Full-text available
About this book: This Open Access volume highlights how tree ring stable isotopes have been used to address a range of environmental issues from paleoclimatology to forest management, and anthropogenic impacts on forest growth. It will further evaluate weaknesses and strengths of isotope applications in tree rings. In contrast to older tree ring s...
Article
Full-text available
Plain Language Summary In the middle of a hot and dry summer, we often think that a large rain event can “rescue” a forest from drought. However, it is not clear whether trees can or do consistently use the water from summer rains. A growing body of research indicates that over the course of the summer growing season, trees take up significant amou...
Article
Full-text available
Temperature and precipitation changes are crucial for larch trees growing at high-elevation sites covered by permafrost in the Altai-Sayan mountain range (ASMR). To contextualize the amplitude of recent climate fluctuations, we have to look into the past by analyzing millennial paleoclimatic archives recording both temperature and precipitation. We...
Article
Full-text available
Carbon (C) allocation plays a crucial role for survival and growth of the alpine treeline trees, which, however, is still poorly understood. Using in situ 13CO2 labeling, we investigated the leaf photosynthesis and the allocation of 13C labeled photoassimilates in various tissues (leaves, twigs and fine roots) in treeline trees and low-elevation tr...
Preprint
Full-text available
Recent studies have challenged the interpretation of plant water isotopes obtained through cryogenic vacuum distillation (CVD) based on observations of large 2H-fractionations. These studies have hypothesized the existence of a H-atom exchange between water and organic tissue during CVD extraction with the magnitude of H-exchange related to relativ...
Article
Full-text available
Wildfires are one of the most important environmental factors controlling forest ecosystem physiology and the carbon balance in the permafrost zone of North Siberia. We investigated tree-ring width (TRW) and stable isotope chronologies in tree-ring cellulose (δ13CCell, δ18OCell) of Larix Gmelinii (Rupr.) Rupr. from a wet (WS) and a dry (DS) site. T...
Chapter
The environmental and physiological interpretation of stable isotope variation in organic matter is affected by many different and interacting factors. This is especially true when considering isotope variation in tree rings, which are influenced not only by leaf-level photosynthetic gas exchange processes but also by post-photosynthetic fractionat...
Chapter
Full-text available
This chapter aims at summarizing strengths and caveats on the suitability of stable carbon and oxygen isotopes in tree rings as recorders for fingerprints of environmental influences. First, environmental constraints limiting tree growth and shaping tree species distribution worldwide are discussed. Second, examples are presented for environmental...
Chapter
Full-text available
Anthropogenic activities such as industrialization, land use change and intensification of agriculture strongly contribute to changes in the concentrations of atmospheric trace gases. Carbon dioxide (CO 2 ), oxidized N compounds(NOx), sulfur dioxide (SO 2 ) and ozone(O 3 ) have particularly significant impacts on plant physiology. CO 2 , the substr...
Chapter
Full-text available
Nutritive, but detrimental if at high levels, several nitrogen (N) forms involved in air and soil biogeochemical reactions constitute the N load trees assimilate. Although a large body of literature describes series of tree-ring N isotopes (δ ¹⁵ N) as archival systems for environmental changes, several questions relative to the isotopic integrity a...
Preprint
Full-text available
The combined study of C and O isotopes in plant organic matter has emerged as a powerful tool for understanding plant functional response to environmental change. The approach relies on established relationships between leaf gas exchange and isotopic fractionation to derive a series of model scenarios that can be used to draw inferences about chang...
Article
Full-text available
The uptake of carbon dioxide (CO2) from the atmosphere through photosynthesis is accompanied by an inevitable loss of water vapor through the stomata of leaves. The rate of leaf-level CO2 assimilation per unit stomatal conductance, i.e. intrinsic water-use efficiency (WUEi), is thus a key characteristic of terrestrial ecosystem functioning that is...
Article
Full-text available
Rapid changes in the hydrological and temperature regimes over the past decades at the northern latitudes enhance significantly permafrost degradation accelerating carbon release, increase the frequency of drought events and extensive wildfires. However, the mechanisms and dynamics driving drought events and their influence on Siberian forests are...
Article
Recent climatic changes significantly affected forest ecosystems in northern Eurasia. Trees growing in Siberia are very sensitive to climate change due to strong temperature limitation of their growth. Our study covers high-latitude (northeastern Yakutia, eastern Taimyr, central Evenkia) and high-altitude (Russian Altai) zones in Eurasia, where tre...
Presentation
Picea abies and Fagus sylvatica are important tree species in Europe, but their physiological performance under climate change at temperate sites is not yet fully understood. We, investigated tree-ring width and stable isotope chronologies (δ13C/δ18O) at 10 sites in Central Europe. In these uneven-aged stands, we compared the year-to- year variabil...
Article
Picea abies (L.) Karst. and Fagus sylvatica (L.) are important tree species in Europe, and the foreseen increase in temperature and vapour pressure deficit (VPD) could increase the vulnerability of these species. However, their physiological performance under climate change at temperate and productive sites is not yet fully understood, especially i...
Article
Full-text available
A strong increase in the mean annual air temperature during the past 50 years by up to 0.54 °C was recorded in the Altai region (45°–52° N; 84°–99° E) compared to the global value of 0.07 °C over the period 1901–2008. The impact of the climatic changes on the hydrology are complex in these mountainous forest ecosystems and not fully understood. We...
Article
Full-text available
Newly developed millennial δ13C larch tree-ring chronology from Siberia allows reconstruction of summer (July) vapor pressure deficit (VPD) changes in a temperature-limited environment. VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm Anomaly. The most humid conditions in the Siberian North w...
Article
Full-text available
The carbon isotopic composition (δ¹³C) of foliage is often used as proxy for plant performance. However, the effect of N O 3 – vs. N H 4 + supply on δ¹³C of leaf metabolites and respired CO2 is largely unknown. We supplied tobacco plants with a gradient of N O 3 – to N H 4 + concentration ratios and determined gas exchange variables, concentrations...
Article
Full-text available
The carbon and oxygen isotopic composition of water and assimilates in plants reveals valuable information on plant response to climatic conditions. Yet, the C and O uptake, incorporation, and allocation processes determining isotopic compositions are not fully understood. We carried out a dual-isotope labelling experiment at high humidity with 18O...
Article
In many regions, drought is suspected to be a cause of Scots pine decline and mortality, but the underlying physiological mechanisms remain unclear. Because of their relationship to ecohydrological processes, δ18O values in tree rings are potentially useful for deciphering long-term physiological responses and tree adaptation to increasing drought....
Article
Full-text available
Wildfires are an important factor in controlling forest ecosystem dynamics across the circumpolar boreal zone. An improved understanding of their direct and indirect, short- to long-term impacts on vegetation cover and permafrost–vegetation coupling is particularly important to predict changes in carbon, nutrient and water cycles under projected cl...
Article
Full-text available
Stratospheric volcanic eruptions have had significant impacts on the radiation budget, atmospheric and surface temperatures, precipitation and regional weather patterns, resulting in global climatic changes. The changes associated with such eruptions most commonly result in cooling during several years after events. This study aimed to reveal eco-p...
Article
Full-text available
Recent decades have been characterized by increasing temperatures worldwide, resulting in an exponential climb in vapor pressure deficit (VPD). VPD has been identified as an increasingly important driver of plant functioning in terrestrial biomes including being a major contributor in recent drought‐induced plant mortality, independently from other...
Article
Full-text available
A multimedia approach is presented to evaluate the atmospheric impact on Alpine torests in Switzerland. The aim of this approach is the determination of anthropogenic air pollutants leading to wet and dry depositions in an area along the Sankt Gotthard transect crossing the Alps in the North-South direction and to evaluate the possible changes in t...
Article
Stable carbon isotopes in tree rings are a promising tool in palaeoclimate research, provided attempts are made to disentangle climatic from local effects (e.g. soil properties, competition, light). The 13 C/ 12 C variations in cellulose of tree rings of beech (Fagus sylvatica) were determined at several sites in the Swiss Central Plateau covering...
Article
Full-text available
The 18O‐signature of atmospheric water vapour (δ18OV) is known to be transferred via leaf water to assimilates. It remains, however, unclear how the 18O‐signal transfer differs among plant species and growth forms. We performed a 9 h greenhouse fog experiment (relative humidity ≥ 98%) with 18O‐depleted water vapour (‐106.7‰) on 140 plant species of...
Article
Full-text available
Stomata control the gas exchange of terrestrial plant leaves, and are therefore essential to plant growth and survival. We investigated gas exchange responses to vapor pressure deficit (VPD) in two grey poplar (Populus × canescens) lines: wild type (WT), and abscisic acid-insensitive (abi1) with functionally impaired stomata. Transpiration rate in...
Presentation
Climatic effects on Picea abies and Fagus sylvatica, two of the most important tree species in Europe, have been extensively investigated. However, their physiology at temperate sites is not yet fully understood. For each species, we sampled five sites along a climate gradient in Central Europe. Tree-ring width and stable isotope ratios (C and O) w...
Article
Full-text available
mDatabases describing branch gas exchange of Picea abies L. at two montane forest sites, Lägeren, Switzerland (National Forschungsprojekt 14 of the Schwei-zerische Nationalfonds) and Oberwarmensteinach, Ger-many (Bayerische Forschungsgruppe Forsttoxikologie), were analyzed in conjunction with a physiologically based model. Parameter estimates for d...
Article
Full-text available
Stratospheric volcanic eruptions have far-reaching impacts on global climate and society. Tree rings can provide valuable climatic information on these impacts across different spatial and temporal scales. To detect temperature and hydroclimatic changes after strong stratospheric Common Era (CE) volcanic eruptions for the last 1500 years (535 CE un...
Article
Full-text available
Rain recharges soil water storages and either percolates downward into aquifers and streams or is returned to the atmosphere through evapotranspiration. Although it is commonly assumed that summer rainfall recharges plant-available water during the growing season, the seasonal origins of water used by plants have not been systematically explored. W...
Article
Elevated CO2 along with rising temperature and water deficits can lead to changes in tree physiology and leaf biochemistry. These changes can increase heat- and drought-induced tree mortality. We aim to reveal the impacts of climatic drivers on individual compounds at the leaf level among European larch (Larix decidua) and mountain pine (Pinus mugo...
Article
Measurements of methane (CH4) mole fractions and δ¹³C−CH4 that resolve the diel cycle in the agriculturally dominated Reuss Valley, Switzerland, were used to quantify the contributions of different CH4 sources to the atmospheric CH4 source mix. Both a nocturnal (NBL) and a diurnal convective boundary layer (CBL) approach were employed. A diel cours...
Article
Full-text available
The tree-ring stable carbon and oxygen isotope chronologies from two forest sites located in the Forni Glacier forefield (Italy)—one along the glacier stream (GL) and the other toward the valley slope (SL)—were analyzed with the aim of disentangling the precipitation and glacier meltwater inputs in source water δ¹⁸O, as reflected by the tree-ring c...
Article
Studies of stable isotopes of water in the environment have been fundamental to advancing our understanding of how water moves through the soil-plant-atmosphere continuum; however, much of this research focuses on how water isotopes vary in time, rather than in space. We examined the spatial variation in the δ18O and δ2H of throughfall and bulk soi...
Article
Full-text available
Rain recharges soil water storages and either percolates downward into aquifers and streams, or is returned to the atmosphere through evapotranspiration. Although it is commonly assumed that summer rainfall recharges plant-available water during the growing season, the seasonal origins of water used by plants have not been systematically explored....
Article
Studies of stable isotopes of water in the environment have been fundamental to advancing our understanding of how water moves through the soil‐plant‐atmosphere continuum; however, much of this research focuses on how water isotopes vary in time, rather than in space. We examined the spatial variation in the δ18O and δ2H of throughfall and bulk soi...
Article
Full-text available
Stable isotopes ratios in tree rings have become an important proxy for paleoclimatology, particularly in temperate regions. Yet, temperate forests are often characterized by heterogeneous stand structures, and the effects of stand dynamics on carbon (δ¹³C) and oxygen isotope ratios (δ¹⁸O) in tree rings are not well explored. In this study we inves...
Article
Full-text available
For more than two decades, research groups in hydrology, ecology, soil science, and biogeochemistry have performed cryogenic water extractions (CWEs) for the analysis of δ²H and δ¹⁸O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soi...
Article
Full-text available
Stratospheric volcanic eruptions have far-reaching impacts on global climate and society. Tree rings can provide valuable climatic information on these impacts across different spatial and temporal scales. Here we explore the suitability of tree-ring width (TRW), maximum latewood density (MXD), cell wall thickness (CWT), and δ¹³C and δ¹⁸O in tree-r...
Article
Full-text available
Increasing biodiversity has been linked to higher primary productivity in terrestrial ecosystems. However, the underlying ecophysiological mechanisms remain poorly understood. We investigated the effects of surrounding species richness (monoculture, two‐ and four‐species mixtures) on the ecophysiology of Lithocarpus glaber seedlings in experimental...
Article
Full-text available
In this commentary, we build on discussions that emerged during the workshop "Isotope-based studies of water partitioning and plant-soil interactions in forested and agricultural environments" held in San Casciano Val di Pesa, Italy, in September 2017. Quantifying and understanding how water cycles through the Earth's critical zone is important to...
Article
Full-text available
We investigated seasonal variations in δ 13 C values and concentrations of carbohydrates and organic acids in needles of declining and healthy mountain pine (Pinus mugo ssp. uncinata (DC.) Domin) trees from the Swiss National Park (SNP), using compound-specific isotopes analysis (CSIA). Our goal was to study the impact of climatic drivers on the in...
Poster
Full-text available
The poster shows an overview of experiments, focusing on the importance of d18O of water vapour on the d18O of plant organic material.
Article
Full-text available
For more than two decades, research groups in hydrology, ecology, soil science and biogeochemistry have performed cryogenic water extractions for the analysis of δ²H and δ¹⁸O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soil water...
Article
Drought is a major environmental constraint to trees, causing severe stress and thus adversely affecting their functional integrity. European beech (Fagus sylvatica L.) is a key species in mesic forests that is commonly expected to suffer in a future climate with more intense and frequent droughts. Here, we assessed the seasonal response of leaf ph...
Article
Full-text available
Our understanding of how temporal variations of atmospheric water vapour and its isotopic composition (δ(18) OV ) influence water and assimilates in plants remains limited, restricting our ability to use δ(18) O as a tracer of ecophysiological processes. We exposed oak (Quercus robur) saplings under wet and dry soil moisture conditions to (18) O-de...
Article
Full-text available
Understanding climate change impacts on drought-prone forests is a critical issue. We investigated ring-width and stable isotopes (Δ¹³C and δ¹⁸O) in two Pinus sylvestris stands of the cold-dry Siberian forest-steppe growing under contrasting climatic trends over the last 75 years. Despite regional warming, there was increasing precipitation during...
Article
Time series of tree-ring growth show significant increases since the early 1970s at the alpine tree line, with simultaneously increasing temperatures and atmospheric CO2 concentration. For a comprehensive understanding of this growth change, the physiological response patterns at both the leaf and stem level need to be separately analyzed and ident...
Article
Rationale: Levoglucosan is formed from cellulose during biomass burning. It is therefore often used as a specific tracer to quantify the contribution of wood burning to the aerosol loading. The stable oxygen isotope composition (δ(18) O value) of biomass is determined by the water cycle and varies regionally, and hence the δ(18) O value of levoglu...
Article
The ability of treeline conifers in the Central European Alps to cope with recent climate warming and increasing CO 2 concentration is still poorly understood. We determined basal area increment (BAI) and tree ring stable carbon isotope ratios (δ 13 C) of Pinus cembra trees from 1925 through 2013. Stable isotope ratios and BAI were compared with le...
Article
Full-text available
A growing number of studies have described the direct absorption of water into leaves, a phenomenon known as foliar water uptake. The resultant increase in the amount of water in the leaf can be important for plant function. Exposing leaves to isotopically enriched or depleted water sources has become a common method for establishing whether or not...
Article
Full-text available
Rationale: In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups (δ (2) Hmethoxyl values) as a palaeoclimate proxy in dendrochronology. This is a quite new method in the field of dendrochronology and the sample preparation is much simpler than the methods used before to measure δ(2) H values from wood. Methods: W...
Article
Full-text available
Adjustment mechanisms of trees to changes in soil-water availability over long periods are poorly understood, but crucial to improve estimates of forest development in a changing climate. We compared mature trees of Scots pine (Pinus sylvestris) and European larch (Larix decidua) growing along water-permeable channels (irrigated) and under natural...