Christian Ammer

Christian Ammer
University of Göttingen | GAUG · Department of Silviculture and Forest Ecology of the Temperate Zones

About

352
Publications
233,216
Reads
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16,668
Citations
Additional affiliations
September 2007 - present
University of Göttingen
Position
  • Professor (Full)
September 1996 - September 2001
Technical University of Munich
Position
  • Research Assistant
April 1992 - September 1996
Ludwig-Maximilians-Universität in Munich
Position
  • Research Assistant

Publications

Publications (352)
Article
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Temperate mixed forests are currently experiencing severe drought conditions and face increased risk of degradation. However, it remains unclear how critical tree physiological functions such as sap flow density (SFD) and tree water deficit (TWD, defined as reversible stem shrinkage when water is depleted), respond to extreme environmental conditio...
Article
Die Ess- oder Edelkastanie (Castanea sativa Mill.) wird als eine Baumart angesehen, die mit den prognostizierten wärmeren und in der Vegetationszeit niederschlagsärmeren Bedingungen infolge des Klimawandels gut zurechtkommen könnte. Ihre zunehmende Einbringung beziehungsweise Förderung in den Laubmischwäldern Mitteleuropas erscheint daher als sinnv...
Article
Several regional initiatives and reporting efforts assess the state of forest biodiversity through broad-scale indicators based on data from national forest inventories. Although valuable, these indicators are essentially indirect and evaluate habitat quantity and quality rather than biodiversity per se. Therefore, their link to biodiversity may be...
Article
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The introduction of non‐native tree species has become a global concern and may disrupt native communities and related ecosystem functions. Soil food webs regulate organic matter decomposition and nutrient cycling in forests with their feeding activities, but evaluating consequences of the introduction of tree species on soil invertebrates is chall...
Article
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Enriching tree species–poor and less productive forests by introducing economically valuable species is a strategy proposed for achieving multipurpose forest management. However, empirical evidence from managed and mature forests on the impact of this enrichment on ecological (multidiversity and ecosystem multifunctionality) and economic dimensions...
Article
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Forest ecosystems face threats related to human-driven degradation, climate change, and biodiversity loss. Addressing these challenges requires management strategies that combine biodiversity conservation with climate change mitigation. Here, we aimed to identify manageable local-scale forest properties that promote biodiversity at multiple trophic...
Article
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The density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 mil...
Article
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Introduction In production forests, management can have cascading effects on biodiversity and ecosystem services. Acoustic diversity reflects the diversity of vocalizing animals and has also considerable recreational value for human well-being, but the relationship between acoustic diversity and forest management remains largely unexplored Method...
Article
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Mixed-species forests are, for multiple reasons, promising options for forest management in Central Europe. However, the extent to which interspecific competition affects tree hydrological processes is not clear. High-resolution dendrometers capture sub-daily variations in stem diameter; they can simultaneously monitor stem growth (irreversible cha...
Article
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In Central Europe, anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s, however, they are still abundant across many forest landscapes. Artificial and natural tree regeneration both play a key role during conversion by determining the species composition and structure of the future for...
Article
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Biodiversity loss and its potential threat on ecosystem functions call for a critical evaluation of human impacts on forest ecosystems. Management practices based on stand diversification offer a possible solution to biodiversity loss due to monoculture plantations, and these practices often involve planting introduced tree species. Although introd...
Article
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The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous for...
Article
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Recent studies suggest that arthropod diversity in German forests is declining. Currently, different national programs are being developed to monitor arthropod trends and to unravel the effects of forest management on biodiversity in forests. To establish effective long-term monitoring programs, a set of drivers of arthropod diversity and compositi...
Article
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Key message Norway spruce operates with larger hydraulic safety margins (HSM) than beech and Douglas-fir despite the known drought sensitivity of spruce, questioning a pivotal role of HSM in drought tolerance. Abstract The exceptional 2018/2019 drought exposed Central Europe’s forests to severe stress, highlighting the need to better understand st...
Preprint
Full-text available
The density of wood is a key indicator of trees’ carbon investment strategies, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here, we analyze information from 1.1 million...
Preprint
Full-text available
Several regional initiatives and reporting efforts assess the state of forest biodiversity through broad-scale indicators based on data from national forest inventories. Although valuable, these indicators are essentially indirect and evaluate habitat quantity and quality rather than biodiversity per se. Therefore, their link to biodiversity may be...
Preprint
Full-text available
Ecosystems worldwide face threats related to human-driven degradation, climate change, and biodiversity loss. Addressing these challenges requires management strategies that combine biodiversity conservation with climate change mitigation. Here, we aimed to identify local-scale management actions that promote biodiversity at multiple trophic levels...
Article
There are growing doubts about the true role of the common mycorrhizal networks (CMN or wood wide web) connecting the roots of trees in forests. We question the claims of a substantial carbon transfer from ‘mother trees’ to their offspring and nearby seedlings through the CMN. Recent reviews show that evidence for the ‘mother tree concept’ is incon...
Article
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Formation of mineral-associated organic matter (MAOM) supports the accumulation and stabilization of carbon (C) in soil, and thus, is a key factor in the global C cycle. Little is known about the interplay of mineral type, land use, and management intensity in MAOM formation, especially on subdecadal time scales. We exposed mineral containers with...
Article
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Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system¹. Remote-sensing estimates to quantify carbon losses from global forests2–5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these est...
Article
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Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, ever...
Article
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Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5-7, we explore how the phy...
Article
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Zerbe S, Lange F, Seliger A, Leitinger G, Ammer C (2023) Wie invasiv ist die Douglasie? Ein Fallbeispiel aus dem Spessart. AFZ-DerWald 16/2023: 30-34. Die Douglasie gilt im Kontext des Klimawandels als vergleichsweise stabile Nadelbaumart, weshalb sie vor allem in Mischung vermehrt berücksichtigt wird. Ob die Verjüngung der Douglasie in Mitteleuro...
Article
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Intensive ungulate browsing significantly impacts forests worldwide. However, it is usually not single browsing events that lead to sapling mortality, but the little-researched interactions of browsed saplings with their biotic and abiotic environment. (I) Our objective was to assess the impact of ungulate browsing on the growth of young saplings r...
Article
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Planted monocultures of even-aged coniferous tree species are abundant worldwide but increasingly damaged by biotic and abiotic stressors and disturbances. In Central Europe, a fundamental goal of ecologically oriented forest management is thus the conversion of pure and often even-aged coniferous stands into structurally more diverse and mixed bro...
Article
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Abstract Cultivation of non‐native tree species is a promising option to adapt managed forests to climate change. However, consequences of non‐native tree species on flora, fauna, and microorganisms that occur in forest ecosystems (forest associates) need to be considered when managing forests. We lack a solid understanding of how cultivating non‐n...
Article
Forest biodiversity studies conducted across Europe use a multitude of forestry terms, often inconsistently. This hinders the comparability across studies and makes the assessment of the impacts of forest management on biodiversity highly context-dependent. Recent attempts to standardize forestry and stand description terminology mostly used a top-...
Article
The European biodiversity and forest strategies rely on forest sustainable management (SFM) to conserve forest biodiversity. However, current sustainability assessments hardly account for direct biodiversity indicators. We focused on forest multi-taxon biodiversity to: i) gather and map the existing information; ii) identify knowledge and research...
Article
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Context Establishing mixed forest stands is an option for improving soil nutrient conditions and for increasing the resilience of forest ecosystems. Aims Identify the effects on soil chemistry of spruce and Douglas fir admixed in European beech forest. Methods We analysed pure and mixed species stands in Germany. The pure stands were mature Europ...
Article
The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion an...
Article
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1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all importa...
Article
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Many studies show that mixed species stands can have higher gross growth, or so-called overyielding, compared with monocultures. However, much less is known about mortality in mixed stands. Knowledge is lacking, for example, of how much of the gross growth is retained in the standing stock and how much is lost due to mortality. Here, we addressed t...
Article
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Soil respiration is rarely studied at the landscape scale where forest and soil properties can be important drivers. We performed forest and soil inventories in 150 temperate forest sites in three German landscapes and measured in situ soil CO2 efflux with the soda-lime method in early summer 2018 and 2019. Both years were affected by naturally occ...
Article
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It is already well known that the effects of tree diversity on aboveground wood productivity depend on tree species identity and site conditions and thus can vary among different tree mixtures and forest sites. The effects of species diversity, specifically on belowground productivity and dynamics, have rarely been studied, so potential interaction...
Article
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Key message Authors have analyzed the possible correlation between measurements/indicators of forest structure and species richness of many taxonomic or functional groups over three regions of Germany. Results show the potential to use structural attributes as a surrogate for species richness of most of the analyzed taxonomic and functional groups...
Article
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Increasing pressure on land resources necessitates landscape management strategies that simultaneously deliver multiple benefits to numerous stakeholder groups with competing interests. Accordingly, we developed an approach that combines ecological data on all types of ecosystem services with information describing the ecosystem service priorities...
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Forest management has a direct influence on the structure and stability of forests. In this study, we used the 3D data from mobile laser scanning in real forest stands dominated by European beech (Fagus sylvatica L.) to simulate different silvicultural treatments and assess their impact on the structural complexity and short-term economic return. F...
Article
Intensification of land use by humans has led to a homogenization of landscapes and decreasing resilience of ecosystems globally due to a loss of biodiversity, including the majority of forests. Biodiversity-ecosystem functioning (BEF) research has provided compelling evidence for a positive effect of biodiversity on ecosystem functions and service...
Article
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Unlabelled: With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme dr...
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Background The ability of overstory tree species to regenerate successfully is important for the preservation of tree species diversity and its associated flora and fauna. This study investigated forest regeneration dynamics in the Cat Ba National Park, a biodiversity hotspot in Vietnam. Data was collected from 90 sample plots (500 m ² ) and 450 su...
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Key message In beech stands, thinning affects growth differently along tree stems, with higher and longer duration increment at stem base than at crown base while unmanaged stands depict opposite patterns. Abstract Forest management affects individual tree growth dynamics at different levels of the tree bole. Here, we assessed stem-growth patterns...
Chapter
From an ecological perspective, forestry interventions can be defined as disturbances actively implemented at different spatial scales with the aim of obtaining a variety of forest-based ecosystem services. By changing the spatial and temporal distributions of resources, they alter competition between trees at the individual, species, and generatio...
Article
Forest management has been shown to affect biodiversity, but the effects vary among taxa and studies. Due to their host-tree preferences, many saproxylic, i.e. deadwood-dependent, beetle species are likely affected by forest management via changes in tree species composition. However, further structural differences caused by forest management, such...
Article
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Environmental filters—including those resulting from biotic interactions—play a crucial role during the assembly of ecological communities. The importance of scale has thereby been acknowledged but filters at different scales have rarely been quantified in relation to each other, although these hierarchically nested filters eventually determine whi...
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Plant species diversity and composition play crucial roles in many ecosystem services and are largely influenced by environmental conditions, as well as natural and/or anthropogenic disturbances. However, our knowledge of the drivers of plant species diversity and composition in the limestone forests of Vietnam, a hotspot of biodiversity, is limite...
Article
Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented. In this study, we investigated the patterns of species...
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The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increases with species richness, although the ecological fundamentals have mainly been investigated through diversity experiments. To adequately manage forest ecosyste...
Article
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Ecosystem functioning may directly or indirectly—via change in biodiversity—respond to land use. Dung removal is an important ecosystem function central for the decomposition of mammal faeces, including secondary seed dispersal and improved soil quality. Removal usually increases with dung beetle diversity and biomass. In forests, dung removal can...
Article
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The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we...
Article
Eine Arbeitsgruppe aus Vertreterinnen und Vertretern von Ressorteinrichtungen des Bundes und der Länder im Bereich Forstwirtschaft und Naturschutz stellt Thesen zur Entwicklung eines nationalen Biodiversitätsmonitorings im Wald vor. Ziel des Monitorings ist es, umfassende, repräsentative Informationen zur biologischen Vielfalt in den Wäldern Deutsc...
Article
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Heterogeneity of structure can increase mechanical stability, stress resistance and resilience, biodiversity and many other functions and services of forest stands. That is why many silvicultural measures aim at enhancing structural diversity. However, the effectiveness and potential of structuring may depend on the site conditions. Here, we reveal...
Article
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Common myrtle (Myrtus communis L.) occurs in (semi-)arid areas of the Palearctic region where climate change, over-exploitation, and habitat destruction imperil its existence. The evergreen shrub is of great economic and ecological importance due to its pharmaceutical value, ornamental use, and its role in urban greening and habitat restoration ini...
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Der Deutsche Verband Forstlicher Forschungsanstalten (DVFFA) beleuchtet in seinem zweiten Beitrag der Serie „Fakten zum Thema: ...“ die Rolle der Wälder in Bezug zur Holznutzung.
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In ihrem Leserbrief in der Ausgabe 4/2022 [5] zur DVFFAFaktenpublikation „Wälder und Klimaschutz“ [2] konstruieren die Autoren einen „Paradigmenwechsel“ in der deutschen Forst- und Holzwirtschaft hin zu einer auf reinen Nutzungsverzicht fokussierten Waldsicht, der angeblich durch die angesprochene DVFFA-Faktenpublikation unterstützt werde. Sind ihr...
Book
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Am 2. und 3. November 2021 trafen sich in Braunschweig Fachleute aus der waldbezogenen Biodiversitätsforschung und dem Monitoring, um fundierte Ideen und Vorschläge zur Erstellung eines nationalen Biodiversitätsmonitorings im Wald (NaBioWald) zu sammeln und einen Überblick über das diesbezügliche Meinungs-spektrum zu erlangen. Impulsreferate zeigte...