Special Sessions

Ecological factors relating to herbaceous species richness
Lauchlan Fraser, Department of Natural Resource Sciences and Biological Sciences, Thompson Rivers University, Canada

For decades, plant ecologists have grappled with the question “what controls plant diversity”? Philip Grime’s humped-back model (HBM) proposed in 1973 predicts that there is a unimodal relationship between herbaceous species richness and aboveground biomass such that maximum species richness is found at intermediate biomass, and minimum species richness is found at low and high biomass. The HBM model has been supported by many studies, as well as being rejected by other studies. Last year, in a paper by Peter Adler and others, a comprehensive data set collected by 48 researchers from many countries generally rejected the unimodal relationship between plant diversity and productivity. But, because of methodological criticisms of the Adler paper, there remains uncertainty in the validity of the HBM. In this session, we explore the HBM model and provide a range of studies that test for other factors that may relate to herbaceous species richness.

Niche-based approaches: tackling the link between environment and biota
Jorge Orestes Cerdeira, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Lisboa, Portugal & Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisboa, Portugal and
Aldina Franco, School of Environmental Sciences, University of East Anglia, Norwich, UK

Since Hutchinson’s pioneering work on niche theory dating from 1957, many modelling approaches inspired in that theory have been proposed. Each model translates a particular view on how species and communities relate to environment and proposes solutions for species spatial distribution, environment suitability and vegetation distribution. While much progress has been achieved, a number of relevant questions about modelling the relation between environment, species and communities remain unsolved and require further investigation. On the occasion of the 110th anniversary of Hutchinson’s birth, we propose a special session on the topics listed below. The session aims to bring together ecologists who work under Hutchinson’s niche theory and an audience of vegetation science experts towards the development of conceptual and methodological frameworks relating species and communities with environment. Contributors will be encouraged to share their thoughts and advances, and to discuss hot issues like:
(i) ascertaining patterns within the ecological niche space;
(ii) selecting the environmental variables that best discriminate communities;
(iii) measuring the dispersion extent of suitable environment for communities, to allow identification of endangered communities;
(iv) removing the pervasive autocorrelation from ecological data; assessing environmental drivers on species invasiveness;
(v) evaluating environmental preferences of geographically separated populations;
(vi) validating species-environment models.

Past vegetation patterns
Triin Reitalu, Institute of Geology, Tallinn University of Technology, Estonia and
Petr Kuneš, Department of Botany, Charles University in Prague, Czech Republic

Knowledge of past vegetation development and processes behind it is an important prerequisite for understanding the patterns in present-day vegetation and plant diversity. Written records (historical maps, historical vegetation records) allow to assess vegetation changes happening over decades or centuries. In addition, fossil pollen profiles can be used to reconstruct changes in vegetation composition and to evaluate the extent and type of land-use over several thousands of years. Recent advances in climate and vegetation modelling, together with paleoecological data offer valuable insights into the processes behind past vegetation patterns. One important issue, where knowledge on past vegetation patterns is of crucial importance, is the question of how much the long-term vegetation changes are due to anthropogenic influence as opposed to natural causes (climate, soil development). Even though, contemporary and palaeo plant ecology deal with similar sets of questions, the interaction between the two disciplines is limited. The objectives of the proposed special session are:
1) to introduce recent developments in palaeoecological research and modelling of past vegetation to the broad audience of vegetation scientists in the IAVS symposium;
2) to facilitate dialogue between people from different disciplines dealing with past vegetation patterns and past biodiversity.

Soil biota shaping vegetation: impact of the invisible world on visible patterns
Mari Moora, Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Estonia

Predominant frameworks in vegetation ecology have an aboveground bias that neglects soil micro-organisms, which is inconsistent with recent work illustrating the importance of soil microbes in terrestrial ecology. While soil microbial effects have been incorporated into plant community dynamics using frameworks of niche modification and plant-soil community feedbacks, their actual role in shaping plant community structure and composition in the nature is understudied. This is mainly due to the cryptic lifestyle and major methodological constraints when studying the natural distribution patterns of soil microbiota, but also due to the fact that vegetation scientists typically address traditionally developed concepts (e.g. competition, dispersal, herbivory). In this session we present and discuss recent studies which elucidate the role of soil biota in shaping outcome of plant distribution, plant-plant interactions and hence plant community composition and diversity patterns. Our aim is to increase awareness about the role of soil biota among vegetation scientists. This knowledge is essential if we want to understand, maintain and restore natural vegetation patterns.