The effects of soil disturbance on the diversity and function of mycorrhizal fungi in grasslands
Pål Axel Olsson (project leader)
Summary of results with list of publications from Microbiological Ecology, Lund University.
Email: pal_axel.olsson@ekol.lu.se
Unseen fungi are of key importance in the food chain
Mycorrhizal fungi live in symbiosis with plants. They grow in the roots of the plants and deliver nutrients to the plant, and at the same time receive from the plant the carbohydrates they need. There are several types. One common type is formed between our forest trees and large fungi such as sickeners, milk caps and chantarelles. Another common type is formed on practically all herbaceous plants and many trees. This type is called arbuscular mycorrhiza (AM) and they are really hidden. They form no sporophores that are visible above ground. But their spores are of key importance in the fungal world. Those who research into fungal genuses have had great difficulty in determining the origin and genus of these fungi. Some fungi form widespread networks of mycelia which are disrupted when the soil is subject to ploughing and rotavation. Such disruption naturally occurs in arable land and is presumably the reason that there are so few AM fungi that proliferate in arable soil. But there are also natural disturbances such as tramping by animals and soil erosion.
The investigations clearly showed that soil disturbance is important for the preservation of species richness. This study is the first one that focused on the way these fungi are affected by soil disturbance in semi-natural grasslands. The effects were similar to those seen in agriculture. The mycelia are broken up and their carbon sequestration ability is reduced. The impact on these fungi is therefore a significant cause of carbon losses from the soil, but at the same time limitation of soil disturbance may be of the utmost importance in preserving quantities of threatened species in nature.
Scientific basis for biodiversity-focused recommendations for forestry in South-East Asia
Lena Gustafsson (project leader)
Summary of results from SLU.
Email: lena.gustafsson@ekol.slu.se
If biodiversity is to be preserved in rain forests in the long term, it is essential to develop methods for a more environmental forestry. Rain forests in south-east Asia are dominated by trees that are called dipterocarps, and many of these are valuable for forestry. When recommendations for nature conservation are developed, they must be based on knowledge of the critical factors for different species, and on knowledge of the ecological processes and patterns that charactise these forests.
When forestry is adapted to nature conservation, it is important that the natural dynamics should be taken into consideration, i.e. the fact that dipterocarp forests are seldom subject to large disturbances. This means that the plants are adapted to fairly constant environmental conditions without large open spaces. Forestry should therefore be based on selective felling so that only a few trees are extracted per felling occasion. In this way a continual tree cover will be maintained that is connected to the landscape. In some forest types such as peat swamps, heath forests and submontane forests, forestry practices should be completely avoided since even selective felling may cause irreversible damage to the ecosystem. There are considerable gains to be made by running a sensitive and sustainable forestry in rain forests. Apart from a potential for rich biodiversity, they also sequestrate a lot of carbon.
Processes that delay or prevent recovery of the vegetation in eutrophied boreal forest land when nitrogen input decreases
Annika Nordin (project leader)
Summary of results from SLU
Email: Annika.Nordin@genfys.slu.se
Growth in boreal forests is normally limited by access to nitrogen. Since the 1950s, increased fallout of atmospheric nitrogenous compounds has affected the Swedish forest ecosystem. Forest fertilisation was therefore used as a measure to increase growth. Nitrogen fallout and nitrogenous fertilisers may affect the structure and function of the ecosystem. Nitrogen induced vegetation changes often persist long after nitrogen input had ended.
In order to determine the long term consequences of increased nitrogen input, it is important to understand whether the systems are at all able to return to their original state if the nitrogen input decreases or ceases. The aim of the project was to investigate biogeochemical processes that can pevent or delay the recovery of the forest ecosystem from the impact of nitrogen.
The project shows that changes in vegetation caused by nitrogen persist even if nitrogen fallout or forest fertilisation ceases. This is probably due to the fact that the turnover of nitrogen in the soil (nitrogen mineralisation) proceeds at a greater rate in previously affected soil. On the other hand, the associations of dwarf shrubs with micorrhizal fungi are not affected by increased nitrogen input. More nitrogen in the forest often gives rise to more grasses and herbaceous plants, while there may be fewer dwarf shrubs and mosses.
Selection of genotypes with high nitrogen utilisation, high weed competitive ability and high allelopathy in wheat and barley for organic farming
Nils-Ove Bertholdsson (project leader)
Summary of results with list of publications from SLU
Email: nils-ove.bertholdsson@ltj.slu.se
In an earlier project, a selection method was developed for the selection of plants with vigorous growth of root and shoots for better nutrient utilisation and resistance to weeds. Since it is expensive to produce root and shoot biomass, there is a risk that competitive genotypes are removed at an early stage. The plant’s production of growth retarding substances that are excreted via the root (allelopathy) is also of importance for competitive ability. The focus of this work has therefore been on developing varieties with a higher allelopathic activity and to verify the effects in field trials.
The project has shown that it is possible to increase nitrogen uptake when access to nutrients is limited by selecting barley plants with vigorous initial root growth. In spring wheat the results are more varied. Not all the selected lines produce an expected high nitrogen uptake. The project has also shown that allelopathy may be of great significance for the ability to compete with weeds. But this trait gradually disappears unless attention is paid to this improvement. A simple crossing and selection programme increases allelopathic activity and the expected increase in weed competitive ability is realised.
Different legume symbioses and their nitrogen fixation in the field
Kerstin Huss-Danell (project leader)
Smmary of results with list of publications from SLU
Email: kerstin.huss-danell@njv.slu.se
In biological nitrogen fixation, nitrogen gas in air is converted into ammonium. This process can only be performed by a few bacteria. One important group are different species of Rhizobium that infect the roots of leguminous plants. The ammonium that is formed is used by the legume which thus has access to a usable form of nitrogen. The nitrogen becomes available to the ecosystems via degradation of dead plants, urine and dung from cattle. It is therefore a key process in the nitrogen cycle. Nitrogen fixation by leguminous plants is of fundamental importance in organic agriculture. The objective of this project was to quantify nitrogen fixation in legumes under realistic growing conditions.
All the studied legumes developed hydrogen gas from the root nodules. This formation of hydrogen gas can be seen as waste of energy in the nitrogen fixation process, but the hydrogen gas can also be seen as the addition of an energy source for microorganisms in the soil which will enhance soil processes such as mineralisation that improves nutrient supply for the crops.
Potassium dynamics in agricultural soil – quantification of sources and sinks and identification of soils that need a potassium increment
Ingrid Öborn (project leader)
Summary of results with list of publications from Soil Sciences, SLU
Email: ingrid.oborn@mv.slu.se
The objective of this research theme was to integrate knowledge of ecological processes on a major scale in order to evaluate and develop methods for the preservation of biodiversity and to improve the biological control in organic farming. Four doctoral theses and over 30 scientific articles and chapters in books have been produced within this project.
The project has demonstrated that organic farming usually results in greater biodiversity and improved control, but that the response to an improved farming system varies between groups of organisms and also between different landscapes. This makes it difficult to develop general support systems without considering specific conditions. The results also show that there is a coupling between the view of farmers regarding nature and the diversity that is found on their farms.
How does hybridisation affect the probability that one species is eradicated when two species meet?
Anna Qvarnström (project leader)
Summary of results with list of publications from Uppsala University
Email: Anna.Qvarnstrom@ebc.uu.se
Because of the ongoing large scale change in the earth’s mean temperature, many species are forced to change their geographical distribution. This means that species that had previously been separated come into contact with one another, despite their pronounced negative effects on one another. Many species are forced to cohabit with the devil. Closely related species are expected to compete for similar resources, and if their relationship is close enough they may even hybridise. There are however few studies which show what effects this has in wild populations.
Pied flycatchers and collared flycatchers have recently come into contact with one another on Öland and Gotland and provide a unique study system for the factors which favour coexistence.
Emissions of greenhouse gases from slurry during storage and when spread on the field
Lena Rodhe (project leader)
Summary of results with list of publications from Institute of Agricultural and Environmental Engineering
Email: lena.rodhe@jti.se
When manure is handled, greenhouse gases which contribute to global warming are emitted, such as methane when slurry is stored and nitrous oxide from land on which manure had ben spread. Our knowledge is however inadequate as regards the emission of greenhouse gases from Swedish agriculture since there is a shortage of measured data.
On Swedish farms established methods are used to reduce losses of plant nutrients which reduces eutrophication and acidification. In many regions slurry containers must be coveed and on spreading the manure must be worked into the soil as quickly as possible to reduce the emission of ammonia.
The principal objective of the project was to identify measures that limit the emissions of both greenhouse gases and ammonia from slurry under Swedish climatic and handling conditions. Annual emissions of nitrous oxide and methane from containers and after spreading of slurry from cattle and pigs were quantified. A study was also made of how emissions are affected by external conditions such as temperature and humidity and the way the manure is stored and spread. This knowledge will make it possible to identify optimal measures for slurry that minimise emissions of both greenhouse gases and ammonia. This is a step towards an environmentally sustainable Swedish agriculture.