Joachim Paul Töpper

• Doctor of Philosophy
• Researcher at Norwegian Institute for Nature Research

Following rapid climate change across the Arctic, tundra plant communities are experiencing extensive compositional shifts. One of the most prevalent changes is the encroachment of boreal species into the tundra (‘borealization’). Borealization has been reported at individual sites, but has not been systematically quantified across the tundra biome...

Global warming is changing plant communities due to the arrival of new species from warmer regions and declining abundance of cold‐adapted species. However, experimentally testing predictions about trajectories and rates of community change is challenging because we normally lack an expectation for future community composition, and most warming exp...

Cost of bacteriophage resistance (COR) is important in explaining processes of diversification and coexistence in microbial communities. COR can be expressed in different traits, and the lack of universally applicable methods to measure fitness trade‐offs makes COR challenging to study. Due to its fundamental role in growth, we explored protein syn...

Arctic and alpine tundra ecosystems are large reservoirs of organic carbon1,2. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere3,4. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain5–7. This hampers the accuracy of global land carbon...

Aims A number of modelling frameworks exist to aid in the identification and exploration of stable states and the assessment of resilience from ecological datasets. However, because such models are complex to implement there is a substantial barrier for the application in ecological research. Here we develop a flexible model of ecological resilienc...

One of the ways in which plants are responding to climate change is by shifting their ranges to higher elevations. Early life‐history stages are major bottlenecks for species' range shifts, and variation in seedling emergence and establishment success can therefore be important determinants of species' ability to establish at higher elevations. Pre...

Ecology & Evolution has published its first Registered Report and offers the perspective of the editor, author, and student on the publication process.

Seed regeneration is a critical stage in the life histories of plants, affecting species' abilities to maintain local populations, evolve, and disperse to new sites. In this study, we test for local adaptations to drought in germination and seedling growth of two alpine forbs with contrasting habitat preferences: the alpine generalist Veronica alpi...

Alien species constitute one of the major threats to global biodiversity. Stopping alien species at an early stage, preferably before establishment, is crucial for the effectiveness of management actions. To enable early detection and prevent future introductions, knowledge of pathways of introduction and their absolute and relative importance is c...

Plants are responding to climate change by shifting their ranges to higher elevations. These range shifts are not happening at the same rate for all species, for example, subalpine species are generally moving faster upslope than alpine species, but with large variation within groups. This asymmetry in migration rates will result in novel communiti...

Despite their importance in shaping the structure and function of marine microbial food webs, little is known about factors regulating marine virus abundance. Previous work demonstrated clearance of laboratory‐cultured Emiliania huxleyi virus by the appendicularian Oikopleura dioica; however, the applicability of this interaction to natural virus a...

Genetic differentiation and phenotypic plasticity jointly shape intraspecific trait variation, but their roles differ among traits. In short-lived plants, reproductive traits may be more genetically determined due to their impact on fitness, whereas vegetative traits may show higher plasticity to buffer short-term perturbations. Combining a multi-t...

Sustainable nature management and ecosystem conservation depends critically on scientifically sound and stakeholder-relevant analytical frameworks for monitoring and assessing ecological condition. Several general frameworks are currently being developed internationally, including the Essential Biodiversity Variables (EBV), and the UN’s SEEA EEA Ec...

Phenotypic plasticity can mask population genetic differentiation, reducing the predictability of trait-environment relationships. In short-lived plants, reproductive traits may be more genetically determined due to their direct impact on fitness, whereas vegetative traits may show higher plasticity to buffer short-term perturbations. Combining a m...

Wooded hay meadows provide livestock fodder in the form of both foliage from pollarded trees and hay from the understorey, and can be part of an environmentally friendly agroforestry system. However, trees may also have a negative effect on fodder production. Such trade-offs between productivity and sustainability in farming are poorly understood,...

Seed dispersal and local filtering interactively govern community membership and scale up to shape regional vegetation patterns, but data revealing how and why particular species are excluded from specific communities in nature are scarce. This lack of data is a missing link between our theoretical understanding of how diversity patterns can form a...

Effective evidence-based nature conservation and habitat management relies on developing and refining our methodological toolbox for detecting critical ecological changes at an early stage. This requires not only optimizing the use and integration of evidence from available data, but also optimizing methods for dealing with imperfect knowledge and...

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a...

Restoration of degraded ecosystems may take decades or even centuries. Accordingly, information about the current direction and speed of recovery provided by methods for predicting time to recovery may give important feedback to restoration schemes. While predictions of time to recovery have so far been based mostly upon change in species richness...

Climate change is a worldwide threat to biodiversity and ecosystem structure, functioning, and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate‐change impacts across the soil–plant–atmosphere continuum...

Dispersal dynamics and local filtering processes interact to generate regional vegetation patterns, but data on their relative importance in nature is scarce. Here, we compare seed and adult plant communities at twelve grassland sites with different climates in southern Norway to explore the degree to which community membership is shaped by dispers...

Species composition is a vital attribute of any ecosystem. Accordingly, ecological restoration often has the original, or “natural,” species composition as its target. However, we still lack adequate methods for predicting the expected time to compositional recovery in restoration studies. We describe and explore a new, ordination regression‐based...

This report is part of the development of a system for determining ecological status. The main purpose of the report has been to develop suggestions for reference and limit values for good condition of indicators that are ready or almost ready for use

Climate warming poses considerable challenges for alpine plant species, especially for competitively inferior ones with resource-conservative adaptations to cold climates. The Himalayas are warming at rates considerably faster than the global average, so it is particularly important to assess how and through which mechanisms alpine plant species ar...

In climate‐change ecology, simplistic research approaches may yield unrealistically simplistic answers to often more complicated problems. In particular, the complexity of vegetation responses to global climate change begs a better understanding of the impacts of concomitant changes in several climatic drivers, how these impacts vary across differe...

Appendicularians are planktonic marine tunicates with elaborate filter-feeding houses that can efficiently trap particles as small as 0.2 um. While marine viruses are seldom considered outside their role in disease transmission, we conducted a controlled laboratory experiment to determine if the appendicularian Oikopleura dioica can trap and ingest...

Factors controlling the community composition of marine heterotrophic prokaryotes include organic-C, mineral nutrients, predation, and viral lysis. Two mesocosm experiments, performed at an Arctic location and bottom-up manipulated with organic-C, had very different results in community composition for both prokaryotes and viruses. Previously, we s...

Questions Is there a shift from positive to negative biotic interaction effects on seedling recruitment along two different stress gradients, temperature and precipitation (the stress‐gradient hypothesis); do such interaction effects differ between species with different bioclimatic affinities? Location Boreal, sub‐alpine and alpine grassland in s...

Inducible plant defense is a beneficial strategy for plants, which imply that plants should allocate resources from growth and reproduction to defense when herbivores attack. Plant ecologist has often studied defense responses in wild populations by biomass clipping experiments, whereas laboratory and greenhouse experiments in addition apply chemic...

Environmental cueing that restricts seed germination to times and places where mortality risk is relatively low may have considerable selective advantage. The predictive power of lab germination responses for field regeneration behaviour is rarely tested. We screened 11 alpine grassland forbs for germination behaviour predictive of microsite and se...

Soil seed banks offer plants the possibility to disperse through time. This has implications for population and community dynamics, as recognised by ecological and evolutionary theory. In contrast, the conservation and restoration literature often find seed banks to be depauperate, weedy and without much conservation value or restoration potential....

Biotic interactions are often ignored in assessments of climate change impacts. However, climate-related changes in species interactions, often mediated through increased dominance of certain species or functional groups, may have important implications for how species respond to climate warming and altered precipitation patterns. We examined how a...

How plants allocate biomass to different parts strongly affects vegetation dynamics and ecosystem processes and services such as productivity and carbon storage. We tested the hypothesis that plant size explains the majority of variation in the size of plant parts (as predicted by Allometric Partitioning Theory, APT) and that additional variation i...

QuestionsWhat are the most important factors explaining present-day variation in species composition in a glacier foreland? Does the rate of species compositional change in glacier forelands decelerate through primary succession? How do data set properties and analytic methods influence our understanding of glacier foreland successional dynamics?Lo...

Millennia of human land-use have resulted in the widespread occurrence of what have been coined ‘domesticated ecosystems’. The anthropogenic imprints on diversity, composition, structure and functioning of such systems are well documented. However, evolutionary consequences of human activities in these ecosystems are enigmatic. Calluna vulgaris (L....

QuestionsEffects of climate on flowering performance are often investigated independently of plant size. We ask how temperature and precipitation impact flowering probability and flower production: via direct effects, size-dependent indirect effects, changes in minimum size for flowering and/or changes in reproductive investment. LocationTwelve cal...

Disturbance in the form of different management regimes affects established vegetation, but how the same management affects the corresponding seed banks is poorly understood. We used the seedling emergence method to investigate how present and previous management intensity impacts the dynamics of established vegetation and corresponding seed bank i...

Background and AimsAcross their range, widely distributed species are exposed to a variety of climatic and other environmental conditions, and accordingly may display variation in life history strategies. For seed germination in cold climates, two contrasting responses to variation in winter temperature have been documented: first, an increased abi...

Seedling recruitment allows genetic recombination and production of dispersal units. Both the climate experienced by the source populations (seed source effect) and the weather experienced by the seeds during germination and seedling emergence (recruitment site effects) are important for seedling recruitment. Separating these effects in the field i...

The phenomenon of individual plants being absent for one or more growing seasons before sprouting again has often been reported for at least 40 years. This has been referred to under the term prolonged vegetative dormancy (from latin «dormire» for «to sleep»), but it has only recently become a topic of study. A range of potential drivers for dorman...

Ocean acidification may stimulate primary production through increased availability of inorganic carbon in the photic zone, which may in turn change the biogenic flux of dissolved organic carbon (DOC) and the growth potential of heterotrophic bacteria. To investigate the effects of ocean acidification on marine bacterial assemblages, a two-by-three...

Questions How frost resistant are the early development stages (seeds, seedlings, plantlets and juveniles) of alpine plant species? Do summer frosts impair establishment of plant species typical of different successional stages on a central alpine glacier foreland? Location Rotmoos glacier foreland, A ustrian C entral A lps ( O bergurgl, T yrol, A...

Ocean acidification may stimulate primary production through increased availability of inorganic carbon in the photic zone, which may in turn change the biogenic flux of dissolved organic carbon (DOC) and the growth potential of heterotrophic bacteria. To investigate the effects of ocean acidification on marine bacterial assemblages, a two-by-three...

The European coastal heathlands are important habitats for international conservation. Today, these low-intensity farming systems are threatened by the cessation of traditional management regimes, such as grazing and prescribed burning. In natural systems, the effects of fire on germination responses are often explained by adaptation to fire over e...

Anthropogenic use of fire, often in conjunction with grazing, is contributing to the creation and maintenance of semi-natural ecosystems on marginal lands world-wide, e.g. the African savannas and the Australian kwongan. The European coastal heathlands are important habitats for international conservation. Today, these low-intensity farming systems...

Infrared differential thermal analysis (IDTA) and differential imaging chlorophyll fluorescence (DIF) were employed simultaneously to study the two-dimensional pattern of ice propagation in leaves and mesophyll freeze dehydration as detected by a significant increase of basic chlorophyll fluorescence (F(0)). IDTA and DIF technique gave different in...