Special Sessions

Acceptance of special session proposals was closed on 15 January 2015

Urban vegetation

Convened by Sonja Knapp & Zdeňka Lososová
Urban vegetation is a heterogeneous assembly of native species, horticultural planting and alien species. It is influenced by multiple factors such as land use, edaphic, and socio-economic conditions, disturbance and stochastic processes. At the same time, some species are under strong selective pressure by human preferences. This session aims to map the recent progress in understanding processes which shape diversity of urban vegetation across different spatial, taxonomic, phylogenetic or functional scales.

Global change and vegetation dynamics: the use of historical data sets

Convened by Radim Hédl, John-Arvid Grytnes, Gerald Jurasinski & Markus Bernhardt-Römermann
The spatial and temporal dynamics of vegetation can be studied at various scales. The ecosystem-level effects of changes in environment during the Anthropocene, when human impact has intensified and gained a global dimension, provide an important framework for the analysis of vegetation change. This includes changes in management of ecosystems, indirect effects of airborne depositions, increased impact of ungulates and, most recently, global climatic changes. The drivers of community composition and related biodiversity changes receive considerable attention by ecologists. A better understanding of this complex process currently belongs to the most important tasks for basic and applied vegetation science.
Fortunately, vast resources of historical vegetation data are available from the 20th century. Sites can be resampled and the data used for comprehensive analyses of vegetation dynamics. The effects of environmental changes on biodiversity and species composition from landscape to global levels are of particular concern. The resampling of records from the 20th century provides a unique opportunity to understand these processes over a period of rapid increase of human impact. However, the resampling of historical sites involves several methodological challenges as well as a need for cooperation between various disciplines. One aspect is how these old vegetation databases (and eventually also new vegetation data that at one stage will become historic data) are retrieved and stored. A second aspect is methods of resampling and comparison with the original sampling. The last and so far least explored aspect is our understanding of processes underlying vegetation change, which calls for intense cooperation with climatologists, geochemists, human geographers and historical ecologists.
The session aims at bringing together vegetation scientists dealing with the resampling of historical vegetation records and their colleagues from other disciplines. On the one hand we seek contributions that present examples of resampling studies. On the other hand we call for contributions that address methodological challenges of resampling studies. Strategies of future research should be discussed, including potential networking not only within the vegetation science community, but also with outreach to disciplines dealing with vegetation history in general.

Long-term perspectives on vegetation change

Convened by: Triin Reitalu, Petr Kuneš & Thomas Giesecke
The time period of plant ecological studies is often restricted to a few years, long-term monitoring programs provide information on the vegetation change over decades, but when the focus lies on vegetation changes over hundreds or thousands of years, palaeoecological techniques have to be used. Several ecological questions require the long time perspective, particularly where long-lived species like trees are involved. Long time perspective is needed to study questions regarding the responses of biomes to climate change, for studies concerned with forest succession, resilience and competition and for evaluating natural versus anthropogenic drivers of vegetation change and diversity. The last million and in particular the last twenty thousand years represent a period for which vegetation dynamics can be reconstructed from pollen and larger plant remains and providing opportunities to study natural experiments that occurred in the past. Recent efforts of quantitative vegetation reconstruction provide improved tools to understand the magnitude of past vegetation changes and to facilitate comparisons of reconstructed and simulated scenarios of long-term vegetation change. We invite ecologists working on different time scales to discuss long term processes and vegetation dynamics based on short term observations, monitoring results, simulations and palaeoecological vegetation reconstructions.

The relevance of ‘dark diversity’ for theoretical and applied ecology

Convened by Francesco de Bello, Rob Lewis & Meelis Pärtel
Describing and understanding the patterns of species diversity presents a major challenge for both theoretical ecologists and conservationists. Ecological theory and biodiversity conservation have traditionally relied on the number and identity of species observed at a site, measured through different sampling techniques and monitoring schemes. However, this observed diversity represents only a portion of the actual ‘habitat-specific species pool’ of a site, that is all species in the region that have an ecological affinity to the prevailing abiotic conditions, and thus the potential to inhabit the site. Absent species that are part of the ‘habitat-specific’ species pool constitute dark diversity. In part, absences may be accountable to insufficient sampling effort both spatially and temporally, or through biotic and abiotic conditions temporarily reducing some species to a less than detectable population size at a given sampling period. Absences capture the dark diversity and can reflect local extinctions, a major concern to nature conservationists, and highly relevant from the restoration and invasion perspective. Considering only observed diversity in ecological studies can therefore have important drawbacks for ecological theory and biodiversity conservation. For example comparing absolute values of species richness across ecosystems, regions and/or taxonomic groups is of limited value since it is not relativized against potential values. Understanding absences facilitates respective comparisons and may improve ways in which biodiversity among regions and habitats is evaluated. Moreover, understanding the mechanisms that regulate biodiversity assembly and species coexistence in a particular site requires identifying which and how many species have been excluded during the assembling process. Understanding absence here is not only valuable but also essential. The session aims to bring together vegetation scientists dealing with different aspects of measuring and studying dark diversity in theoretical and applied ecological studies. The session will cover methodological issues in estimating the absent component of biodiversity, its utility in better understanding shifts in community assembly under global change scenarios and the possible applications for conservation and ecosystem management.

Old wine in new bottles: trait-based understanding of plant responses to disturbance

Convened by Jitka Klimešová & Tomáš Herben
There are few ecological processes that have been studied more thoroughly than disturbance. However, after a surge of interest before and around the turn of the millennium, there have been a number of case studies, but surprisingly few attempts at more general understanding. Apart from a few trivial generalities, we lack knowledge of general patterns of plant traits along disturbance gradients. We even do not know within which trait groups these patterns are to be sought. This is partly due to the fact that study of disturbance has been dominated by study of a few systems such as boreal forests, Mediterranean shrublands, and grazed systems, which makes generalizations difficult. Although disturbance is present in virtually any ecosystem, scholars traditionally used different context-dependent tools to study vegetation response to specific disturbance drivers such as fire, herbivory, flooding, or frost. Second, disturbance is a difficult factor due to its dynamic nature, in contrast to e.g. soil or climatic variables. Time since disturbance and disturbance intensity, together with their spatial and temporal correlations account for multidimensionality of disturbance gradients that has made any generalization difficult. We believe that with the advent of trait-based ecology, we possess novel approaches and tools how these questions can be addressed. We know which traits drive vegetation responses to major environmental gradients and could examine how these traits change along disturbance gradients. We know more about functions and traits of plant bodies that enable plants to survive disturbance in vegetative state. Existing databases offer huge data sets of mean trait values of many species, which can be linked with existing or to-be-collected data on community composition along disturbance gradients. Vegetation databases also offer data to characterize individual species in terms of their optima in response to disturbance gradients. The session aims at bringing together vegetation scientists interested in study of disturbance, particularly when spanning larger gradients of disturbance regimes. We invite comparative studies from different ecosystems assessing functional traits relevant to their disturbance regimes and discuss general framework for plant traits and disturbance type assessment. Most welcome are studies seeking hitherto unstudied traits of species responses to disturbance.

Integration of evolutionary processes into invasion studies - cancelled

Convened by Kate S. He & Tiffany Knight
Concerns for the implications and consequences of successful invasions have stimulated a considerable amount of research in the past two decades. Invasion biologists are continuously searching for answers to questions such as what types of biological traits make a superior invader and what types of communities are more susceptible to invasions. The answers for those two questions have been perused separately in most published studies in recent years, even though invaders’ traits can be best understood in the context of the recipient community as it was proposed by Darwin in 1859. Contemporary studies have shown that for plant invaders, being different in traits and fitness from natives can lead to successful establishments and spread. Therefore, the classic niche theory stating that large overlap in limiting factors can prevent a species from establishing in a novel community, may in part explain invasion success. Other core mechanisms that explain invasion success include disturbances, enemy release, biotic interactions, and rapid adaptations under novel environments. However, evolutionary history of species in both native and introduced ranges has rarely been explored in invasion studies even though it may be a critical factor causing the success or failure of invasions. Therefore, the aim of this special session is to call for contributions that integrate evolutionary processes into current invasion studies by examining the role of phylogenetic structure of both native and exotic communities in invasion processes, and that test phylogenetic relatedness between exotic species and native flora by integrating traits and niche concepts at multiple scales.

Species and plant community responses along soil gradients

Convened by Martin Diekmann, Jörg Ewald & Cord Peppler-Lisbach
Species distribution models relate the large-scale distribution of organisms to environmental predictors, most often by relying on climatic variables. They have become increasingly popular in the framework of climate change research. However, the models often neglect the responses of species to factors other than climate, especially soil variables. The main reason for this is the lack of systematic measurements of the responses of species and communities: whereas hundreds of thousands of compositional plot data are available from all over Central Europe, only few of these plots are accompanied by soil data. Ellenberg values give us an indirect estimate of the optima relative to several soil variables, but there is insufficient knowledge about the critical thresholds, for example with respect to soil pH, beyond species are no longer found. These limits, however, are of critical importance for species distribution models and other fields of ecology, such as conservation biology and restoration ecology. In this session we aim to quantify the responses of species to various soil variables, notably pH and nutrients (nitrogen, phosphorus). We will also discuss methodological aspects related to the detection of ecological thresholds along gradients, i.e. whether there is a boundary clumping of species along soil gradients that coincides with the boundaries of communities.

Vegetation patterns, processes and dynamics of timberlines - only poster session

Convened by Hongyan Liu, Zehao Shen, Lynn Resler & Eryuan Liang
As the marginal belt of forests, timberlines have been hypothesized to be sensitive to environmental changes. Timberlines, including alpine and arctic timberlines, forest-grassland ecotones, and forest-wetland ecotones, are widely distributed. There have been some efforts on monitoring timberline vegetation dynamics under climate changes, but different vegetation indicators were selected in different studies. General features of vegetation and the determinants behind these features are still required for monitoring and comparison at global scale. How trees, shrubs and herbs mix in timberlines is still a conundrum in vegetation science. We aim at bringing together vegetation scientists who have studied timberlines to share timberline vegetation patterns, processes and dynamics in different parts of the world in this session. Works on timberline vegetation monitoring are particularly welcome. This session will improve understanding general patterns of timberline vegetation and responses of timberline to different environmental limitations.

Remote sensing for vegetation science

Convened by Hannes Feilhauer, Duccio Rocchini & Sebastian Schmidtlein
Remote sensing is a valuable complement of field-based data collections since it allows for a synoptic view of an area at a broad range of temporal, spectral and spatial resolutions. New methods and techniques provide measurements of photosynthetic activity, functional traits, plant stress, disturbance, as well as proxies for species richness, functional diversity and plant species composition. The possibility to map traits or species composition as continuous fields in space and time provides new insights into pattern and processes. Recently opened image archives of satellite data and open source systems for the analysis of remotely sensed imagery allow to study large parts of the Earth's surface free of costs. The aim of this session is to give an overview on available methods and applications and to discuss challenging aspects of the use of remote sensing for vegetation science.