Dr Marko Hyvärinen, marko.hyvarinen@oulu.fi
Department of Biology, University of Oulu http://cc.oulu.fi/~biolwww/english/Welcome.html

EXTINCTION RISK AND MANAGEMENT OF RARE PLANTS IN PATCHY SEASHORE HABITATS

Project summary

Seashore meadows of the Bothnian Bay harbour several endemic plant species and arctic plants with a disjunctive distribution area in the Arctic and N parts of the Baltic region (Primula sibirica -group). Species of both groups exhibit more or less patchy population structure. Since local populations of many of the species have been declining during the last decades we aim to examine their population biology and life-history traits in order to be able to recognise the phases that may be most sensitive to external influence. These include amplitude and frequency of disturbance and the impact of herbivory on species coexistence at the local scale. Furthermore, the occurrence of metapopulation structure and its consequences to ecology of these species is under scrutiny. Specifically, we use three plant species belonging to this group (Primula nutans, Arctophila fulva and Puccinellia phryganodes) as surrogate species, first, for investigating how to best protect communities of seashores and seashore meadow habitats, and second, for planning and targeting most efficient management and conservation practices on seashore meadows.

Analysis of population dynamics is achieved by constructing a set of population dynamic models based on field experiments and observations from several years. These can be used to analyse the importance of habitat characteristics to population viability of chosen plant species. Especially the availability and turnover of suitable habitat patches and patch quality will be targeted. Furthermore, the significance of extensive goose grazing in the area in maintenance of local biodiversity is assessed. Both analytical methods and simulations will be employed to determine the critical life-history stages for population survival. This information, together with supportive data from genetic studies, will be used in planning and focusing management practises in optimal way to conserve species diversity in these habitats. The research is managed as a consortium of the research group in the Department of Biology, University of Oulu and the Nature Conservation Department of the North Ostrobothnia Regional Environment Centre.

Research group:

Pirjo Rautiainen, pirjorautiainen(at) hotmail.com
Lauri Erävuori, lauri.eravuori(at) oulu.fi
Marika Niemelä , mniemel(at) mail.student.oulu.fi
Annamari Markkola, amarkkol(at) sun3.oulu.fi
Pirkko Siikamäki, Pirkko.Siikamaki(at) oulu.fi
Jouko Siira, jouko.siira(at) oulu.fi
Jouni Aspi, jouni.aspi(at) oulu.fi
Henry Väre, henry.vare(at) helsinki.fi
Sami Aikio, sami.aikio(at) helsinki.fi
Eero Kaakinen, eero.kaakinen(at) vyh.fi
Tupuna Kovanen, tupuna.kovanen(at) vyh.fi
Juha Markkola, juha.markkola(at) vyh.fi

Project’s own pages: http://cc.oulu.fi/~eravuori/welcome.htm

Progress and results year 2000

Grazing-exclosure study was continued for its second year on Isomatala, Hailuoto. Effects of grazing/ungrazing treatments on salt marsh vegetation with Puccinellia phryganodes was examined by measuring 1) the cover of all species, 2) the maximum heights and 3) the number of flowering shoots of dominant species. So far the results indicate that Puccinellia is more abundant on grazed plots and that grazing depresses the growth and flowering of Agrostis stolonifera, Juncus gerardii and Phragmites australis, the potential competitors of Puccinellia.

Competition experiment between Puccinellia phryganodes and Agrostis stolonifera in the Botanical gardens was started in October. Axillary shoots from 20 ramets of both species were planted alone or both together in pots and grown in summer conditions. Half of the plant material will be cut down imitating mowing/grazing to see how it does affect to the outcome of competition between the species.

At the beginning of June we noticed that exceptionally large amount of flowering shoots of Puccinellia phryganodes were developing both in potted Puccinellia in the Botanical gardens and in the field. A pollination experiment was started in the Botanical gardens but with few exceptions flowers never opened so removal of anthers and hand pollination could not be done. The amount of flowering shoots in pots were counted and in July 70 flowering shoots were collected for further study of the development of flowers and for staining of endophytic fungal infections possibly affecting the flowering. At the beginning of July a trial to document the flowering in the field on Isomatala did not succeed because of wilting of the flowering shoots which made them difficult to be found and because the vegetation was so intensively grazed by geese.

We started an experiment to study the effects of nutrition on growth and survival of Puccinellia in the Botanical gardens. Small axillary shoots were planted in pots with a mixture of peat and sand in July. They were divided in to three groups with two nutritional level and a control with only water addition. We conducted twice the nutritional treatments starting at the end of August. During the autumn plants with additional nutrition seemed to be in much better condition than the control group indicating that the nutritional conditions might have a great impact on growth and survival. This might partially explain the observed variation in vigour of Puccinellia stands in different growing places.

To resolve the potential of mowing as a management tool for overgrowing Puccinellia stands we started an experiment at Siikajoki, Tauvo where the second largest occurrence of the species is situated. At the beginning of September 12 pairs of Puccinellia patches were chosen and marked for the experiment. The cover and location of a patch was measured on a 1m² sample plot with the help of 10 x 10-cm grid. Also the covers of co-occurring species were measured. From the other half of the patch pairs the vegetation was cut down from height of 5-10 cm so that Puccinellia remained untouched. In addition we marked on five treatment pairs individual ramets to follow their demography.

The main populations of Puccinellia phryganodes at Siikajoki and at Hailuoto were mapped with the help of GPS to get more exact data of the present state and distribution. At Siikajoki, Tauvo 108 patches were found and marked. Diameter and cover of half of the patches were measured. Considerably larger amount of patches now observed compared to observations at few previous years probably was simply due to more time used for mapping. Similar mapping was done at southern part of Hailuoto at Väliteonkarit occurrence, which just as Tauvo population consists of small and more or less distinct patches of Puccinellia. Altogether 31 patches or group of patches were found from 13 small skerries. The outer borders of the main population on Isomatala consisting of large and almost uniform Puccinellia stands were also mapped.

For later analysis of genetic diversity within and between the populations of Puccinellia shoot samples were collected and preserved in freezer (-70° C). Material was collected from about 50 patches at Tauvo, Siikajoki, two patcHes at Savilahti, Siikajoki, 30 patcHes at Väliteonkari, Hailuoto and from 25 locations of the borders of Isomatala population, Hailuoto. The total number of samples taken from different populations was about 180 from Tauvo, 10 from Savilahti, 280 from Isomatala and 100 from Väliteonkarit. In all 570 samples of shoots were collected from about 110 locations.

With Arctophila fulva var. pendulina, the locations of the patches were mapped and sizes of the patches were measured. Moreover, leaf samples were collected for genetic diversity analysis. Management experiment was started and seed samples were collected for germination analysis. Pollen germination analysis was carried out in order to find the reason for non-existent seed dispersal.

A numerical simulation model was constructed for studying the dynamics and evaluating the extinction risk of Arctophila fulva patches under the disturbance regime that prevails at the Liminka Bay. The model will be parameterised with field data on the size-changes of individual patches during 2000 and 2001. A sensitivity analysis of the model helps to understand the factors that are most important for the long-tem persistence of the A. fulva.

With Primula nutans demographic data include now one transition in natural and managed sites. The species seems to have at least a short-term seed bank, but the seeds are unable to float as such. The seeds submerge immediately, but after germination these raise to the water surface and are able to spread along with moving water. Small population seemed to suffer at some localities of biased flower ratios (pin versus thrum), which leads to lowered seed production and further to lowered seed germination. Thus conservation selection process should consider only large populations with relatively even flower type ratios. The garden experiment indicates, that the species do not suffer on nutrient limitation and produce readily new stolons which forms new rosettes. In a garden experiment the life cycle may be completed within one year, but in native sites this seems improbable.

 

Project publications, pub2.