Christian Körner

University of Basel | UNIBAS · Department of Environmental Sciences, Institute of Botany

Maintaining or increasing forest carbon sinks is considered essential to mitigate the rise of atmospheric CO2 concentrations. Harvesting trees is perceived as having negative consequences on both the standing biomass stocks and the carbon sink strength. However, harvesting needs to be examined from a forest stand canopy perspective since carbon ass...

High‐latitude vegetation experience different temperatures than the ambient air temperature. While lacking a regional plant temperature product, we drove the dynamic ecosystem model, LPJ‐GUESS, with widely used ERA5‐land surface temperature (Tsurf, at radiative equilibrium) and air temperature to understand ecosystem process responses to these two...

In the European Alps, mean temperature has risen by 2.5 K since the end of the nineteenth century. A 2 K warming of the growing season has taken place in the last 4 decades only. The 2.5 K warming should rise the position of the climatic treeline by about 400 m. Actual shifts in uppermost tree positions reported here for the Austrian Defereggen Val...

Extended growing season lengths under climatic warming suggest increased time for plant growth. However, research has focused on climatic impacts to the timing or duration of distinct phenological events. Comparatively little is known about impacts to the relative time allocation to distinct phenological events, for example, the proportion of time...

High-latitude vegetation can experience much higher surface temperatures (T surf , at radiative equilibrium) than the ambient air temperature (T air ). In snow-free seasons, T surf is closely linked to plant physiological and biochemical processes. We drove the dynamic ecosystem model LPJ-GUESS with reanalysis data ERA5-land T surf and 2-m T air to...

While the position of alpine and arctic treelines can be predicted by climatic data, the underlying biological mechanisms are still unclear. In a recent paper in this journal (Körner C, Lenz A, Hoch G (2023) Chronic in situ tissue cooling does not reduce lignification at the Swiss treeline but enhances the risk of 'blue' frost rings. Alpine Botany...

Background Weather conditions and fungal morphology may influence spatial and temporal dynamics of carbon transfer to ectomycorrhizal fungi from their tree hosts but field studies of these dynamics are challenging. Methods Broad-leaved trees in a Swiss forest were labeled with ¹³C-depleted CO2 from 2001–2005 and ¹³C traced into ectomycorrhizal spo...

The mycorrhizal symbiosis between fungi and plants is among the oldest, ubiquitous and most important interactions in terrestrial life on Earth. Carbon (C) transfer across a common mycorrhizal network (CMN) was demonstrated over half a century ago in the lab (Reid and Woods 1969), and later in the field (Simard et al . 1997). Recent years have seen...

In a recent Perspective, Karst et al. (2023) offered a valuable critical review, warning of over-interpretation and positive citation bias in common mycorrhizal network (CMN) research. It concluded that while there is evidence for C movement among plants, the importance of CMNs remains unclear, as noted by others too (Henriksson et al. 2023). Here...

The alpine life zone is perhaps the only biome that occurs globally where mountains are high enough. At latitudinally varying elevation, the alpine belt hosts small stature plants that vary greatly in morphology, anatomy and physiology. In this contribution, I summarize a number of principles that govern life in what is often considered a cold and...

What is addressed as growing season in terrestrial ecosystems is one of the main determinants of annual plant biomass production globally. However, there is no well‐defined concept behind. Here, we show different facets of what might be termed growing season, each with a distinct meaning: (1) the time period during which a plant or a part of it act...

Mountains represent ‘experiments by nature’ that permit testing ecological theory. Using herbarium samples of 92 Rhododendron species collected between 800 and 4500 m a.sl. in the Himalaya-Hengduan Mountains region, SW China, we explored congeneric elevational trends in key plant traits at the among- and at the within-species level. We aimed at ide...

In their 2013 paper, Lenz et al. illustrated how trees growing at the low-temperature limit respond to a chronic in situ warming or cooling by 3 K, by employing Peltier-thermostated branch collars that tracked ambient temperatures. The micro-coring-based analysis of seasonal tree ring formation included double-staining microtome cross sections for...

Background To assess the extent of belowground carbon transfer to ectomycorrhizal fungi in natural forests, we used δ¹³C and loge C/N measurements to calculate spatial dynamics of carbon movement into ectomycorrhizal sporocarps. Methods Fourteen broad-leaved trees were labeled with ¹³C-depleted CO2 from 2001–2005 in Switzerland and ¹³C traced into...

Forests account for nearly 90 % of the world's terrestrial biomass in the form of carbon and they support 80 % of the global biodiversity. To understand the underlying forest dynamics, we need a long-term but also relatively high-frequency, networked monitoring system, as traditionally used in meteorology or hydrology. While there are numerous exis...

In this contribution, I will summarize a number of features of mountain ecosystems that apply globally. After providing a brief statement on mountain definitions and some mountain statistics, I will recall the major climatic and atmospheric drivers and how their action is modified by geomorphology and type of vegetation. I will close by highlightin...

Tree species differ in their physiological responses to drought, but the underlying causes are often unclear. Here we explored responses of radial growth to centennial drought events and sap flow (Fs) to seasonal drought in four mixed forests on either moist or drier sites in northwestern Switzerland. While the diffuse-porous species (Fagus sylvati...

Background. The spatial extent and timing of carbon fluxes from mature trees to ectomycorrhizal fungi associated with different hosts is challenging to assess in natural forests but could provide insights into carbon dynamics of fungi differing in exploration capabilities. Methods. We analyzed carbon movement into ectomycorrhizal sporocarps at the...

Mountain areas provide essential resources for a significant proportion of the Earth’s population. This study presents the development of mountain research between 1900 and 2019 based on peer-reviewed articles in English listed in Web of ScienceTM (WOS). We analyzed the number of publications over time, journals and scientific categories, frequent...

Aim Initiation of autumnal leaf senescence is crucial for plant overwintering and ecosystem dynamics. Previous studies have focused on the advanced stages of autumnal leaf senescence and reported that climatic warming delayed senescence, despite the fundamental differences among the stages of senescence. However, the timing of onset of leaf colorat...

Whether and how alpine organismic communities respond to ongoing environmental changes is difficult to assess quantitatively, given their intrinsically slow responses, remote locations and limited data. Here we provide a synthesis of the first five years of a multidisciplinary, highly standardized, long-term monitoring programme of terrestrial and...

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...

A standardized delineation of the world’s mountains has many applications in research, education, and the science-policy interface. Here we provide a new inventory of 8616 mountain ranges developed under the auspices of the Global Mountain Biodiversity Assessment (GMBA). Building on an earlier compilation, the presented geospatial database uses a f...

Aim: Initiation of autumnal leaf senescence is critical for plant overwintering and ecosystem dynamics. Previous studies focused solely on the advanced stages of autumnal leaf senescence and claimed that climatic warming delays senescence, despite the fundamental differences among the stages of senescence. However, the timing of onset of leaf color...

This scientific commentary refers to ‘Forest stand and canopy development unaltered by 12 years of CO2 enrichment’ by Norby et al. (doi: 10.1093/treephys/tpab107). All life requires a balanced presence of c. 18 essential chemical elements other than carbon (C), hydrogen and oxygen (out of c. 94 natural elements on Earth). These rules of stoichiomet...

The majority of alpine plants are of small stature. Through their small size alpine plants are decoupled from the free atmospheric circulation and accumulate solar heat. However, a few alpine species do not follow that “rule” and protrude with their aboveground structures from the microclimatic shelter of the main canopy boundary layer. We aim at e...

We studied abundance, diversity, and composition of soil invertebrates along snowmelt gradients to generally understand how soil animal communities are responding to life conditions across snowbeds along a west–east transect of the European Alps and to create a reference inventory for future investigations of climate change effects on snowbed habit...

Old postcards with stamps might help unravelling historical family stories and relationships. By employing ancient DNA recovered from world war I postage stamps, we disprove a family saga of an illegitimate child born in 1887. We developed a protocol to collect DNA from saliva, trapped and protected on the backside of postage stamps glued on postca...

The alpine belt hosts the treeless vegetation above the high elevation climatic treeline. The way alpine plants manage to thrive in a climate that prevents tree growth is through small stature, apt seasonal development, and ‘managing’ the microclimate near the ground surface. Nested in a mosaic of micro-environmental conditions, these plants are in...

Mountains are rugged structures in the landscape that are difficult to delineate. Given that they host an overproportional fraction of biodiversity of high ecological and conservational value, conventions on what is mountainous and what not are in need. This short communication aims at explaining the differences among various popular mountain defin...

At high elevation or latitude, trees reach low-temperature range limits. In attempting an explanation, the range limits of individual tree species (set by freezing tolerance) and the general limit of the life-form tree (set by thermal growth constraints) need to be distinguished. The general cold edge of the fundamental niche of trees is termed the...

The global treeline phenomenon follows a common high elevation or high latitude isotherm (Körner 2012). Because treeline position (not necessarily the growth rate of trees) is defined by temperature irrespective of season length (beyond a minimum of three months), treeline elevation can be modelled with surprisingly high precision (Paulsen and Körn...

Das Strahlungsangebot, die Versorgung mit Wasser und Mineralstoffen sowie, auf der Basis dieser Voraussetzungen, der Einbau von Kohlenstoff für Wachstum und Biomasseproduktion sind die wichtigsten Bindeglieder zwischen Pflanzen und ihrer physikochemischen Umwelt. Die biochemischen und physiologischen Grundlagen hierzu wurden in früheren Kapiteln be...

Dieses Kapitel beschäftigt sich mit der Entwicklung und Zusammensetzung der Vegetation. Die Pflanzengemeinschaft an einem bestimmten Standort ist zwar letztlich das Resultat enorm komplizierter Wechselwirkungen von erdgeschichtlich jüngeren, historischen und aktuellen Prozessen mit der abiotischen Umwelt (Klima und Ausgangssubstrat; Kap. 26 und 27)...

Die Pflanzendecke der Erde ist das Spiegelbild des Klimas, modifiziert durch regional wirksame Einflüsse des geologischen Untergrunds und von Störungen (◘ Abb. 24.1). So, wie das Klima keine scharfen geografischen Grenzen kennt, gibt es auch keine scharfen Grenzen zwischen den Vegetationszonen, die durch die Dominanz bestimmter Lebensformen geprägt...

Die wissenschaftliche Ökologie beschäftigt sich mit den Wechselwirkungen zwischen Organismen und ihrer lebenden und unbelebten Umgebung. Sie umspannt alle Integrationsebenen vom Einzelorganismus bis zur Biosphäre. Entsprechend vielfältig sind die Forschungsansätze und Teildisziplinen (► Abschn. 21.6).

In the Original publication of the article, the funding number was incorrectly published.

Alpine plants complete their seasonal phenological cycle during two to three snow-free months. Under climate change, snowmelt advances and the risk of summer droughts increases. Yet, photoperiodism may prevent alpine plants from benefiting from an earlier start of the growing season. To identify the drivers of flowering phenology in the seven main...

Does mistletoe infestation influence the position of the dry range limit of oaks? We explored this question and our results contrast most earlier findings on host-mistletoe interaction. The study was located in the SE Himalayas in an environment with 200–360 mm annual precipitation falling mainly during the short monsoon season (hardly any rain dur...

Statements that plant growth or the biomass production of a terrestrial ecosystem is nutrient limited are always true, and hence, reflect a truism that is of limited ecological value. Exceptions may be sites under bird cliffs or on guano benches on oceanic islands, eutrophic estuaries, or plants growing in very deep shade where C limitation rules o...

It is important, though trivial, that low temperatures affect different life processes in different ways. The life process most limited will most strongly influence growth and development. In the nineteenth century, when researchers watched submerged aquatic leaves for emerging air bubbles in order to check whether the plant was photosynthesizing,...

Plants respond to the harsh alpine environment with a high degree of specialization, the structural and functional aspects of which this book aims to explore. Palaeorecords suggest that life on land started out in sheltered, warm, and moist environments, and gradually expanded into more demanding habitats where water is rare, thermal energy is eith...

Conditions for plants have always changed and will always change, everywhere on the globe, and high elevation vegetation is no exception

The alpine flora of a given mountain region commonly contains 200–300 different species of higher plants (Chap. 2). How do they manage to maintain their presence and expand their range into new open land? How do they ensure the maintenance of intra-population diversity required for sustained ground cover in a harsh and ever-changing environment? Th...

The distribution of trees reaches a natural limit somewhere along thermal, drought, or disturbance gradients. The limit set by low temperature at high elevation or high polar latitudes is termed ‘treeline’ (alpine or arctic treeline). Treelines represent an abrupt change in land cover by a dominant life form, a change from tall woody to small, most...

The previous chapters have illustrated that rates of carbon assimilation by leaves are relatively high in alpine plants. Structural investments favor roots rather than stems, but the mean biomass fraction invested in leaves is similar as in comparable morphotypes at low elevation.

Alpine plants acquire water and nutrients from substrates which differ in many respects from those common at lower elevations. Over very short distances one can find a large variety of alpine soil types, ranging from alpine sand drifts to peat bogs, from shallow A/C (e.g. rendzina) soils to the deeply weathered profiles of some alpine grassland soi...

This chapter deserves a preface at the occasion of preparing the third edition of this book. Readers will notice that the majority of the references in this chapter date from the past century. The driver of studying CO2 gas exchange over all these early years (including my own motivation) was a legacy of de Saussure’s discovery of photosynthesis ar...

Walking across an alpine fell field on a bright day, the mountaineer may find it still chilly and windy, and ‘dry’ air may dehydrate the skin. A nearby meteorological station with all its weather masts confirms: +4 °C air temperature, 5 ms–1 wind speed, 40 % relative humidity. While our mountaineer experiences the harsh life in the mountains, the w...

The climate of a steep equator facing slope? The climate in a poleward exposed avalanche track? The climate of an alpine observatory on a windswept ridge? The climate where alpine life occurs, e.g. in the surface of a cushion plant? In winter or in summer? Under overcast or clear sky conditions? In the tropics or in Alaska?

Snow can fall and cover the ground at alpine elevations at any time of the year and at all latitudes. Higher plants can be found in habitats of mean snow duration of anywhere between 320 and a few days (in the tropics) per year.

Cellular aspects of growth have traditionally not been part of alpine plant ecology. It was perhaps taken as self-evident that once plants are in an active phase of life and sufficient carbon assimilates are present at meristems, plants would grow new cells.

Mountain tops, just like hot deserts are among those environments where life is dominated by climatic severity

Plants commonly don’t grow alone. Thus, the growth of an individual leaf or an isolated plant—the topic of the previous three chapters—needs to be placed in the context of interactions, the growth of many other leaves and plants. A slowing down of one individual may be balanced by enhanced growth of another, hence only a consideration of all member...

What does ‘alpine’ mean? One common explanation is that the term is of Latin origin and means ‘white’ or ‘snow-covered’ (from ‘albus’ = white, with reference to the North Italian peaks of the Alps as seen by the Romans; Löve in Arct Alp Res 2:63–73, 1970). However, today linguists consider this as purely coincidental and the term is most likely of...

We are glad that our suggestion that surplus carbon drives allocation and plant–soil interactions has encouraged debate about whether plants trade carbon with microbes in return for nutrients. In his letter, Noë refutes our suggestion that many interactions among above- and belowground ecosystem components can be simply explained by the production,...

While the high elevation limit of trees is commonly related to low temperature, the rear edge of their distribution is often associated with drought. Here we explore phenology traits that contribute to a mechanistic explanation of both these edges of the fundamental niche in the broad leaved evergreen Quercus pannosa s.l. Populations of this specie...

Seit 120 Jahren liegt die Stärke des STRASBURGERs in der ausgewogenen Darstellung aller Teilgebiete der Pflanzenwissenschaften. In der vorliegenden 38. Auflage sind besonders die Teile Struktur und Entwicklung stark überarbeitet worden. • Der Teil Struktur beschreibt den pflanzlichen Aufbau ausgehend von der Ebene der Zelle über die Gewebe bis hin...

The direction of science is often driven by contemporary theory, and theory emerges from consolidated empirical knowledge. What we know emerges from what we explore, and we explore what we have technical tools for. I feel that technical opportunities contributed strongly towards what is held as a contemporary, widely accepted theory. However, the p...

Plant growth is usually constrained by the availability of nutrients, water or temperature, rather than photosynthetic carbon (C) fixation. Under these conditions leaf growth is curtailed more than C fixation, and the surplus photosynthates are exported from the leaf. In plants limited by nitrogen (N) or phosphorus (P), photosynthates are converted...

Die Baumartenvielfalt hat einen Eigenwert, wie biologische Vielfalt überhaupt. Die Biodiversität im Wald auf ihren möglichen Nutzen zu reduzieren greift zu kurz. Ganz erheblich zu kurz greift die aktuelle Diskussion, in der der Wald oft auf seine Kohlenstoffspeicherung und sein Potenzial zum Ersatz von fossilen Brennstoffen reduziert wird, wobei un...

Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substant...

Unlike the well understood cold limit of trees, the causes of the dry trailing edge of trees await explanations. Here we aimed at explaining the drought limit of an evergreen oak species (Quercus pannosa s.l.) in a typical dry valley of the upper Yangtze region, SE Himalaya, where rains (c. 250 mm a‐1) are largely confined to the typical monsoon se...

Unlike the well understood alpine treeline, the upper range limits of tree taxa that do not reach the alpine treeline are largely unexplained. In this study, we explored the causes of the exceptionally high elevation (4,270 m) occurrence of broad-leaved evergreen oaks (Quercus pannosa) in SE Himalayas. We assessed the course of freezing resistance...

In 2018, Central Europe experienced one of the most severe and long-lasting summer drought and heat wave ever recorded. Before 2018, the 2003 millennial drought was often invoked as the example of a “hotter drought”, and was classified as the most severe event in Europe for the last 500 years. First insights now confirm that the 2018 drought event...

The mutualistic symbiosis between forest trees and ectomycorrhizal fungi (EMF) is among the most ubiquitous and successful interactions in terrestrial ecosystems. Specific species of EMF are known to colonize specific tree species, benefitting from their carbon source, and in turn, improving their access to soil water and nutrients. EMF also form e...

In temperate alpine environments, the short growing season, low temperature and a slow nutrient cycle may restrict plant growth more than carbon (C) assimilation does. To test the C-limitation hypothesis, we applied a shade gradient ranging from ambient light to 44% (maximum shade) of incident photon flux density (PFD) in late successional, Carex c...

In the early 19th century, when naturalists were busy cataloging Earth's inventory and separating the living world into labeled units, a 32-year-old explorer at the flanks of Chimborazo mountain in Ecuador—higher than anybody else had climbed by that time—saw the fog clearing, revealing an arena of tropical mountain life. According to his notes, th...

The response of trees to increasing atmospheric CO2 concentrations is often mediated by the availability of nutrients. However, little is known about the influence of CO2 enrichment on nutrient availability in forests with mature trees. We studied processes in the soil under five 35-m-tall Norway spruce trees (Picea abies) in NW Switzerland that we...

All plant species reach a low temperature range limit when either low temperature extremes exceed their freezing tolerance or when their metabolism becomes too restricted. In this study, we explore the ultimate thermal limit of plant tissue formation exemplified by a plant species that seemingly grows through snow. By a combination of studies in al...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

In this review, I discuss, and partly challenge, a number of paradigms, assumptions and definitions that apply to many fields of plant ecology. The main points include the need for a distinction between a growth-or yield-oriented versus a fitness-or biodiversity-oriented concept of limitation and stress, and the challenges of a meaningful handling...

It is generally accepted that animal heartbeat and lifespan are often inversely correlated, however, the relationship between productivity and longevity has not yet been described for trees growing under industrial and pre-industrial climates. Using 1768 annually resolved and absolutely dated ring width measurement series from living and dead conif...

Pollination is an ecosystem function of global importance. Yet, who visits the flower of specific plants, how the composition of these visitors varies in space and time, and how such variation translates into pollination services is hard to establish. The use of DNA barcodes allows us to address ecological patterns involving thousands of taxa that...