The role of seeds in a changing climate - linking germination ecophysiology to population and community ecology
Regeneration from seed is a key event in the life-histories of plants; affecting their ability to disperse, to evolve, and to persist under unfavourable conditions. Consequently, impacts of climate change on the probability of successful recruitment from seed are likely to affect the fate of local populations and communities. This project integrates observational and experimental approaches across broad-scale climate gradients in Norway to explore how climate, and climate change, affects the role of seed recruitment across four levels of organisation - from direct physiological effects via demographic responses to population and community dynamics.
General aim and methodological approach
The general objective of SeedClim is to provide a mechanistic understanding of how ongoing and future climate change affects plants at landscape to regional scales. To achieve this we have developed a new methodological framework allowing us to explore how climate-change effects vary along two major climate gradients--temperature and precipitation--and how these effects scale across levels of organisation from individuals via populations to communities.
- Does climate affect seed recruitment in any systematic way?
- To what extent do differences among populations reflect local adaptations, and to what extent do they reflect plastic responses to the environment?
- At what levels of organisation, from germination physiology via individual performance to population and community dynamics, do climate effects appear?
- How do climate effects link across these levels?
- How will these relationships affect the susceptibility of local communities to climate change - specifically the invasibility of alpine communities?
The western Norwegian fjord landscapes give us a unique possibility to set up a grid of study sites along independent temperature and precipitation gradients, enabling us to study the unique and combined effects of a warmer and a wetter climate. Our 12 experimental sites are located in a climate grid where four levels of annual precipitation (600, 1200, 2000 and 2700 mm) are combined with three levels of mean summer temperatures (7.5, 9.5, and 11.5°C) while keeping all other variables as constant as possible (Figure 1). In collaboration with met.no we have installed climate stations that monitor temperature, precipitation, and soil moisture at each site.
Within the climatic grid, we have transplanted seeds of three species pairs of alpine specialists and lowland generalists (Veronica alpina, V. officinalis, Viola biflora, V. palustris, Carex capillaris, C. pallescens) and turfs (25 x 25 cm) of intact plant communities including focal populations, from cold and/or dry conditions towards warmer and/or wetter conditions. In other words, from the mountains towards the lowlands, and from the inlands towards the coast.
- To provide a background for the mechanistic experimental studies on climate change in this project, we have carried out an empirical modelling study of the spatial distribution of the focal plants and their responses to climate and other variables. A particularly interesting finding was that in addition to the climate effect, the distributions of the alpine species are also affected by interactions from lowland species. This means that theses species might be more negatively affected by future climate change than what their own physiological responses to climate suggests (Meineri et al. in prep).
- To examine patterns of seedling recruitment along the precipitation and temperature gradients we recorded seedling emergence in intact vegetation and in experimentally created disturbances, or gaps, in the 12 sites. In the intact vegetation, seedling emergence increased towards warmer climates in the driest region, but it decreased towards warmer climates in the wetter regions. In gaps, however, the number of germinating seedlings increased with temperature across all regions, and it also increased towards drier regions. This suggests that seedling recruitment into intact vegetation may become harder in a warmer and a wetter climate, and that the ability of species to respond to future climate change by means of colonisation of new areas (range shifts) and/or local adaptation may depend critically on the level of disturbance in the landscapes (Master thesis Berge 2010).
- Seed banks of the grassland communities were extensive; 7988 seedlings germinated per square metre sampled, representing more than 100 different species. The overall similarity between vegetation and seedbank was 62%, but there are significant scale-dependencies and climate-related trends. The seed bank was the major source of seedlings across the climatic grid (23-90% of all seedlings; model estimate 82%), but its relative contribution increased towards cold and dry climates, suggesting that the role of seedbanks may decrease in the future.
- In addition to the experiments, we have measured plant traits and resource allocation in our focal species, as well as species composition and diversity of extant grassland communities to examine how these vary along the natural temperature and precipitation gradients. Preliminary results show contrasting responses in growth and resource allocation to temperature between species. These results show that both precipitation and temperature affect growth and resource allocation in lowland vs. alpine species, and that species-specific responses may affect the competitive relationship between them, favouring the lowland generalist in a warmer and a wetter world (Master theses Bargman 2009, Pötsch 2010).
2011 will mark the end of the initial phase of the project, as we will now start getting results from the transplant experiments.
Two posters (pdfs) presenting interim results can be found at the bottom of this page.
1. Effects of climate on seed production and/or dispersal
Plants depend on seed dispersal for colonization of new habitat patches as well as for "tracking" their ecological niche through space under changing climatic or environmental conditions. Understanding seed dispersal and how it varies between species and along ecological gradients is therefore key to understanding species' distribution in time and space, their responses to climatic and environmental changes, as well as community assembly and biodiversity. Seed dispersal is a "hot topic" and is intensively studied by plant ecologists today, both from empirical (How far and how fast can species spread? Will they be able to displace and colonize new areas in response to future climate change?) and theoretical (What is the relative importance of dispersal and niche processes for community assembly, diversity, and evolution?) points of view.SeedClim offers opportunities for studies of dispersal processes along gradients, as well as for studying the contribution of dispersal processes to community assembly and diversity under different ecological settings.
We seek students who are interested in studying variation in seed production (single species or community approach, studying variation in seed production within and among species in the SeedClim grid) and seedrain (community approach, study seedrain density and species richness in the SeedClim grid).
- How do seed production and/or seed rain vary along climatic gradients?
- How does this vary among species with different ecological and functional traits?
- What are the implications for species' responses to climate change?
- Combine seedrain assessment by means of seed traps and surveys of potential seed sources surrounding the traps to assess dispersal distances.
- Surveys to assess maximum seed production for many species (including model species), per flowering stem and per area. Combine with SeedClim and external data on e.g. recruitment success, range size, plasticity, species' traits, and "niche filling" to understand ecological consequences.
2. Effects of climate, and climate change on seedling survival, growth and reproduction.
In SeedClim, we have transplanted seeds of four model species to warmer, wetter and warmer and wetter climates in order to assess how populations will respond to the climatic changes predicted in our study region. We have already studied the seedling recruitment of our species under extant and predicted future climatic conditions, and we are seeking students who would be interested in following up established experiments with plants grown under of extant and future climates to study consequences of climate change for survival, growth and reproduction of our target species.
- How will plant populations of different species and in different parts of the species' range respond to climate change?
- Are there differences in growth and reproduction along climate gradients, and if so, do these reflect plastic responses to the environment or adaptations to the current local environment?
As target species we have selected two species pairs consisting of an alpine species (Veronica alpina, Viola biflora) and their lowland co-geners (Veronica officinalis, Viola palustris)
- Monitor survival, growth and reproduction, analyse data using generalized linear models.
3. What is the variation in clonal growth structure of the dominant graminoid Agrostis capillaris in relation to climate? A MSc student can collect data on clonal growth traits of the species along climate gradients, and use these data to parameterise an already-existing clonal growth model. This model can then be used to understand consequences of climate change for clonal growth in this important grassland species.
4. How do species traits vary along climate gradients? Site-level traits (notably, maximum height, seed mass, Specific Leaf Area, but also other less standardised traits of presumed functional importance) can be collected for as many species as possible in the different localities. Variation in traits among communities and within species along the gradients complement data on variation and change in biodiversity and community composition (assessed in other parts of the project) and will enable generalization and comparison with other studies.
Vigdis Vandvik UiB, project leader
Olav Skarpaas NINA, population ecology, demography and modelling
Øyvind Nordli met.no, climate data monitoring and modelling
Kari Klanderud postdoc UiB, community ecology
Deborah Goldberg, University of Michigan, community ecology and resource allocation of focal species
Zuzana Münzbergová, Czech Academy of Sciences, population ecology and modelling, genetic analyses
Matt I. Daws, Royal Botanical Gardens, Kew, UK / EWL Sciences, Darwin, Australia, seed ecology
Eric Meineri, UiB, population biology and distributional modelling
Joachim Spindelböck, UiB/HiSF, population biology and seed ecophysiology
Christine Pötsch, UiB, resource allocation
Serge Farinas, University of Michigan, soil nutrient dynamics
Knut Rydgren HiSF, seed and population ecology and demography
Mikael Ohlson UMB, treeline dynamics and tree species establishment
Marianne Evju NINA, population ecology, demography and modelling
Anita Verpe Dyrdal met.no, climate data monitoring and modelling
Funding source: Norwegian Research council (NFR) NORKLIMA 2008-2012
Bargmann T. How are plants responding to a changing climate? A case study of growth and allocation in Veronica alpina, Viola biflora, Veronica officinalis and Viola palustris in western Norway. Master thesis, Oxford University
Berge A. 2010. Seedbank, seedrain and seedling recruitment along climate gradients in southern Norway. Master thesis, University of Bergen
Meineri E, Skarpås O, and Vandvik V. 2010. Predicting alpine plant distributions and climate change: Do biotic interactions matter at the landscape scale? In prep.
SeedClim Fieldwork Foto: Vigdis Vandvik
Last updated 20.4.2011