Below-ground processes in meadow soil under elevated ozone and carbon dioxide : - Greenhouse gas fluxes, N cycling and microbial communities

This thesis focuses on how elevated CO2 and/or O3 affect the below-ground processes in semi-natural vegetation, with an emphasis on greenhouse gases, N cycling and microbial communities. Meadow mesocosms mimicking lowland hay meadows in Jokioinen, SW Finland, were enclosed in open-top chambers and exposed to ambient and elevated levels of O3 (40-50 ppb) and/or CO2 (+100 ppm) for three consecutive growing season, while chamberless plots were used as chamber controls. Chemical and microbiological analyses as well as laboratory incubations of the mesocosm soils under different treatments were used to study the effects of O3 and/or CO2. Artificially constructed mesocosms were also compared with natural meadows with regards to GHG fluxes and soil characteristics. In addition to research conducted at the ecosystem level (i.e. the mesocosm study), soil microbial communities were also examined in a pot experiment with monocultures of individual species. By comparing mesocosms with similar natural plant assemblage, it was possible to demonstrate that artificial mesocosms simulated natural habitats, even though some differences were found in the CH4 oxidation rate, soil mineral N, and total C and N concentrations in the soil. After three growing seasons of fumigations, the fluxes of N2O, CH4, and CO2 were decreased in the NF+O3 treatment, and the soil NH4+-N and mineral N concentrations were lower in the NF+O3 treatment than in the NF control treatment. The mesocosm soil microbial communities were affected negatively by the NF+O3 treatment, as the total, bacterial, actinobacterial, and fungal PLFA biomasses as well as the fungal:bacterial biomass ratio decreased under elevated O3. In the pot survey, O3 decreased the total, bacterial, actinobacterial, and mycorrhizal PLFA biomasses in the bulk soil and affected the microbial community structure in the rhizosphere of L. pratensis, whereas the bulk soil and rhizosphere of the other monoculture, A. capillaris, remained unaffected by O3. Elevated CO2 caused only minor and insignificant changes in the GHG fluxes, N cycling, and the microbial community structure. In the present study, the below-ground processes were modified after three years of moderate O3 enhancement. A tentative conclusion is that a decrease in N availability may have feedback effects on plant growth and competition and affect the N cycling of the whole meadow ecosystem. Ecosystem level changes occur slowly, and multiplication of the responses might be expected in the long run.

Maintaining plant species richness by cattle grazing - mesic semi-natural grasslands as focal habitats

Semi-natural grasslands are the most important agricultural areas for biodiversity. The present study investigates the effects of traditional livestock grazing and mowing on plant species richness, the main emphasis being on cattle grazing in mesic semi-natural grasslands. The two reviews provide a thorough assessment of the multifaceted impacts and importance of grazing and mowing management to plant species richness. It is emphasized that livestock grazing and mowing have partially compensated the suppression of major natural disturbances by humans and mitigated the negative effects of eutrophication. This hypothesis has important consequences for nature conservation: A large proportion of European species originally adapted to natural disturbances may be at present dependent on livestock grazing and / or mowing. Furthermore, grazing and mowing are key management methods to mitigate effects of nutrient-enrichment. The species composition and richness in old (continuously grazed), new (grazing restarting 3-8 years ago) and abandoned (over 10 years) pastures differed consistently across a range of spatial scales, and was intermediate in new pastures compared to old and abandoned pastures. In mesic grasslands most plant species were shown to benefit from cattle grazing. Indicator species of biologically valuable grasslands and rare species were more abundant in grazed than in abandoned grasslands. Steep S-SW-facing slopes are the most suitable sites for many grassland plants and should be prioritized in grassland restoration. The proportion of species trait groups benefiting from grazing was higher in mesic semi-natural grasslands than in dry and wet grasslands. Consequently, species trait responses to grazing and the effectiveness of the natural factors limiting plant growth may be intimately linked High plant species richness of traditionally mowed and grazed areas is explained by numerous factors which operate on different spatial scales. Particularly important for maintaining large scale plant species richness are evolutionary and mitigation factors. Grazing and mowing cause a shift towards the conditions that have occurred during the evolutionary history of European plant species by modifying key ecological factors (nutrients, pH and light). The results of this Dissertation suggest that restoration of semi-natural grasslands by private farmers is potentially a useful method to manage biodiversity in the agricultural landscape. However, the quality of management is commonly improper, particularly due to financial constraints. For enhanced success of restoration, management regulations in the agri-environment scheme need to be defined more explicitly and the scheme should be revised to encourage management of biodiversity.

Meadow plant growth and competition under elevated ozone and carbon dioxide

The main aim of my thesis project was to assess the impact of elevated ozone (O3) and carbon dioxide (CO2) on the growth, competition and community of meadow plants in northern Europe. The thesis project consisted of three separate O3 and CO2 exposure experiments that were conducted as open-top-chamber (OTC) studies at Jokioinen, SW Finland, and a smaller-scale experiment with different availabilities of resources in greenhouses in Helsinki. The OTC experiments included a competition experiment with two- and three-wise interactions, a mesocosm-scale meadow community with a large number of species, and a pot experiment that assessed intraspecific differences of Centaurea jacea ecotypes. The studied lowland hay meadow proved to be an O3-sensitive biotope, as the O3 concentrations used (40-50 ppb) were moderate, and yet, six out of nine species (Campanula rotundifolia, Centaurea jacea, Fragaria vesca, Ranunculus acris, Trifolium medium, Vicia cracca) showed either significant reductions in biomass or reproductive development, visible O3 injury or any two as a response to elevated O3. The plant species and ecotypes exhibited large intra- and interspecific variation in their response to O3, but O3 and CO2 concentrations did not cause changes in their interspecific competition or in community composition. However, the largest O3-induced growth reductions were seen in the least abundant species (C. rotundifolia and F. vesca), which may indicate O3-induced suppression of weak competitors. The overall effects of CO2 were relatively small and mainly restricted to individual species and several measured variables. Based on the present studies, most of the deleterious effects of tropospheric O3 are not diminished by a moderate increase in CO2 under low N availability, and variation exists between different species and variables. The present study indicates that the growth of several herb species decreases with increasing atmospheric O3 concentrations, and that these changes may pose a threat to the biodiversity of meadows. Ozone-induced reductions in the total community biomass production and N pool are likely to have important consequences for the nutrient cycling of the ecosystem.

Helsingin metropolialueen maisemaekologiset muutokset vuosina 1955-2009

Landscape is shaped by natural environment and increasingly by human activity. In landscape ecology, the concept of landscape can be defined as a kilometre-scale mosaic formed by different land-use types. In Helsinki Metropolitan Region, the landscape change caused by urbanization has accelerated after the 1950s. Prior to that, the landscape of the region was mainly only shaped by agriculture. The goal of this study was in addition to describing the landscape change to discuss the factors impacting the landscape change and evaluate thelandscape ecological impacts of the change. Three study areas at different distances from Helsinki city centre were chosen in order to look at the landscape change. Study areas were Malmi, Espoo and Mäntsälä regions representing different parts of the urban-to-rural gradient in 1955, 1975, 1990 and 2009. Land-use of the maps was then digitized into five classes: agricultural lands, semi-natural grasslands, built areas, waters and others using GIS methods. First, landscape change was studied using landscape ecological indices. Indices used were PLAND i.e. the proportions of the different land-use types in the landscape; MPS, SHEI and SHDI which describe fragmentation and heterogeneity of the landscape; and MSI and ED which are measures of patch shape. Second, landscape change was studied statistically in relation to topography, soil and urban structure of the study areas. Indicators used concerning urban structure were number of residents, car ownership and travel-related zones of urban form which indicate the degree of urban sprawl within the study areas. For the statistical analyses, each of the 9.25 x 9.25 km sized study areas was further divided into grids with resolution of 0.25 x 0.25 kilometres. Third, the changes in the green structure of the study areas were evaluated. The landscape change reflected by the proportions of the land-use types was the most notable in Malmi area where a large amount of agricultural land was developed from 1955 to 2009. The proportion of semi-natural grasslands also showed an interesting pattern in relation to urbanization. When urbanization started, a great number of agricultural lands were abandoned and turned into semi-natural grasslands but as the urbanization accelerated, the number of semi-natural grasslands started to decline because of urban densification. Landscape fragmentation and heterogeneity were the most widespread in Espoo study area which is not only because of the great differences in relative heights within the region but also its location in the rural-urban fringe. According to the results, urbanization induced agricultural lands to be more regular in shape both spatially and temporally whereas for built areas and semi-natural grasslands the impact of urbanization was reverse. Changes in landscape were the most insignificant in the most rural study area Mäntsälä. In Mäntsälä, built area per resident showed the greatest values indicating a widespread urban sprawl. The values were the smallest in highly urbanized Malmi study area. Unlike other study areas, in Mäntsälä the proportion of developing land in the ecologically disadvantageous cardependent zone was on the increase. On the other hand, the green structure of the Mäntsälä study area was the most advantageous whereas Malmi study area showed the most ecologically disadvantageous structure. Considering all the landscape ecological criteria used, the landscape structure of Espoo study area proved to be the best not least because of the great heterogeneity of its landscape. Thus the study confirmed the previous results according to which landscape heterogeneity is the most significant in areas exposed to a moderate human impact.

Maiseman- ja luonnonhoidon yleissuunnitelma : Pirkkalankylä–Sionkylä

Perinteisen karjatalouden muovaamat perinnebiotoopit, kuten kedot, niityt, hakamaat ja metsälaitumet, ovat monimuotoisimpia luontoympäristöjämme. Hoidon myötä arvokkaat maisemat säilyvät avoimina. Härkää sarvista on ylimaakunnallinen hanke, jonka tavoitteena on arvokkaiden kohteiden laidunnushoidon järjestäminen. Pirkkalankylä ja Sionkylä on valittu yhdeksi hankkeen kohdealueista, joille on laadittu maiseman- ja luonnonhoidon yleissuunnitelma. Yleissuunnitelmassa on määritelty mahdollisia luonnonlaidunkohteita kuten perinnemaisemia, ranta-alueita ja muita laidunnuksesta hyötyviä kohteita sekä muita maatalousalueiden maiseman- ja luonnonhoitokohteita. Mukana on tietoa hoitomenetelmistä ja rahoitusmahdollisuuksista, ja niistä on myös tiedotettu suunnittelun aikana. Tavoitteena on saada kohteita hoidon piiriin, innostaa maanomistajia ja löytää kohteille hoitajiksi karjatilallisia ja paikallisia yhdistyksiä. Mahdolliset hoitotoimenpiteet perustuvat täysin vapaaehtoisuuteen. Hankkeen puitteissa voidaan avustaa kohteiden hoidon suunnittelussa ja rahoitusten hakemisessa. Syksyllä 2009 jaettiin alueen asukkaille infokirje ja kysely hoitoa kaipaavista kohteista. Maastotöitä tehtiin syksyllä 2009. Yleissuunnitelmassa on otettu huomioon kyselyssä ilmi tulleita alueita sekä aiemmissa selvityksissä todettuja alueita. Lisäksi on tarkasteltu tärkeissä tiemaisemissa näkyviä kohteita. Härkää sarvista- hankkeen toiminta-aika on 1.6.2009–31.5.2012. Hanketta

Teiskon maiseman- ja luonnonhoidon yleissuunnitelma

Perinteisen karjatalouden muovaamat perinnebiotoopit, kuten kedot, niityt, hakamaat ja metsälaitumet, ovat monimuotoisimpia luontoympäristöjämme. Hoidon myötä arvokkaat maisemat säilyvät avoimina. Härkää sarvista on ylimaakunnallinen hanke, jonka tavoitteena on arvokkaiden kohteiden laidunnushoidon järjestäminen. Tampereen Teisko on valittu yhdeksi hankkeen kohdealueista, joille on laadittu maiseman- ja luonnonhoidon yleissuunnitelma. Yleissuunnitelmassa ovat mukana arvokkaat perinnebiotoopit, jotka on inventoitu 1990-luvulla. Lisäksi mukaan on valittu kohteita, jotka ovat lajistoltaan monimuotoisia, riittävän suuria laidunnuskohteiksi tai sijaitsevat maisemallisesti keskeisillä paikoilla. Suunnitelma sisältää tietoa hoitomenetelmistä ja rahoitusmahdollisuuksista, ja niistä on myös tiedotettu suunnittelun aikana. Tavoitteena on saada kohteita hoidon piiriin, innostaa maanomistajia ja löytää kohteille hoitajiksi karjatilallisia ja paikallisia yhdistyksiä. Mahdolliset hoitotoimenpiteet perustuvat täysin vapaaehtoisuuteen. Hankkeen puitteissa voidaan avustaa kohteiden hoidon suunnittelussa ja rahoitusten hakemisessa. Yleissuunnittelun maastotyöt ja tiedotus toteutettiin kesän ja syksyn 2010 aikana. Härkää sarvista- hankkeen toiminta-aika on 1.6.2009–31.5.2012. Hanketta toteuttavat Keski-Suomen, Pirkanmaan, Etelä-Pohjanmaan ja Etelä-Savon ELY-keskukset sekä alueelliset ProAgriat.