Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Abstract Boreal urban forests are becoming more and more fragmented and, at the same time, are exposed to low-level but long-term nitrogen and sulphur deposition. Natural mid-boreal forests are dominated by few tree and shrub species, while herbs and grasses are rare. Soils in mid-boreal forests are rich in ectomycorrhizal (ECM) fungi, forming a symbiotic relationship with forest trees, which is important for the nutrient cycle especially in nutrient-poor ecosystems. Aims of this thesis were 1) to study differences between mid-boreal urban and rural forests in composition of macrofungi and structure of plant communities, 2) to explore whether responses of Scots pine seedlings to excess N are mediated via soil or via air, and 3) to study if partial removal of vegetation and humus layer alleviates the adverse effects of excess N on plant and fungal communities, and promotes performance and regeneration of Scots pine in urban forests. The growth responses of seedlings and their mycorrhizal colonization were studied in both field and greenhouse experiments. Peroxidase (POD) activity was used as a root stress indicator. Urban forests were poor in number of fruiting ECM fungal species, but rich in herbs and grasses in the field layer, as compared to rural forests. These differences were thought to result from changes in soil properties. ECM fungal colonization in Scots pine roots did not respond significantly to high nitrogen load in soil, but high root POD activity indicated changes in root physiology. ECM macrofungal diversity in urban forests was not markedly increased during a five-year survey after a partial humus removal treatment. On the other hand, fruiting of Cortinarius semisanguineus is a positive response to the treatment. Scots pine seedling emergence was poor due to rapid revegetation at the urban sites, but the treatment promoted both root and shoot growth of planted Scots pine seedlings in urban forests. Decreased root POD activity in Scots pine seedlings in the humus removal treatment possibly indicates lowered root stress. Soil manipulations may result in a risk of nutrient leakage, and a risk of invasion by non-typical plants. Also, small stand size with high recreation pressure causes a risk for tree regeneration in urban forest stands. These risks need to be considered when planning management of urban coniferous forests.

Today, it is well known that biological diversity is decreasing worldwide, and the presence of indicator species can identify areas with high biological diversity. Environments with a high presence of indicator species are important to protect and preserve in the form of, for example, nature reserves as these environments indicate high nature values. The aim of this study is to find out whether the coniferous forest's indicator species have the greatest species density and occurrence within the boundaries of the nature reserves in Dalarna, Sweden. The distribution of 10 different indicator species within the coniferous forests of Dalarna, Sweden, was mapped in the QGIS software and the total species density inside as well as outside the nature reserves of Dalarna was compared in the statistical program SPSS. The species density of five selected indicator species was compared inside versus outside of the reserves. The result for the 10 indicator species showed that there was no significant difference between inside versus outside of the reserves, although there were a higher species density per hectare outside the boundaries of the nature reserves. The result for the five selected indicator species showed no significant difference between inside versus outside of the reserves, however, the species density of both R.subpinnatus and P.grossa were higher within the boundaries of the nature reserve. More sightings of indicator species outside the boundaries of nature reserves may indicate that the public is more inclined to report sightings in unprotected areas, rather than reporting sightings in protected areas that have already been established as having high nature values. Many species observations are found just outside the boundaries of the nature reserve, which may indicate that high nature values occur there as well. Further studies about potential buffer zones and their impact on indicator species are encouraged. / Att den biologiska mångfalden minskar världen över är idag välkänt, signalarter är arter som vars närvaro kan tyda på en miljö som kan generera en bra grund för hög biologisk mångfald. Miljöer med hög närvaro av signalarter är viktiga att skydda och bevara i form av exempelvis naturreservat eftersom dessa miljöer tyder på höga naturvärden. Denna studies frågeställning är om barrskogens signalarter har störst arttäthet och förekomst inom naturreservatens gränser. Med hjälp av artobservationer från Artportalen kartlades 10 olika signalarters utbredning i Dalarnas barrskogar i programvaran QGIS. Därefter jämfördes den totala arttätheten för studiens alla arter per hektar innanför och utanför Dalarnas naturreservat i statistikprogrammet SPSS för att se om det fanns en signifikant skillnad mellan respektive område. Även arttätheten för fem utvalda signalarter jämfördes för att se om det fanns en signifikant skillnad mellan de skyddade och icke-skyddade områdena. Resultatet visade att det inte fanns en signifikant skillnad mellan områdena (p=>0,05), även om det var fler artobservationer per hektar utanför naturreservatens gränser. Resultatet för de enskilda arternas arttäthet per hektar och område visade att det inte fanns någon signifikant skillnad mellan områdena, dock var arttätheten för både R.subpinnatus och P.grossa högre inom naturreservatens gränser. Att det förekommer fler observationer av signalarter utanför naturreservatens gränser kan bero på att allmänheten kan vara mer benägna att rapportera in fynd som gjorts i oskyddade områden, i stället för att rapportera in eventuella fynd i skyddade områden som redan har konstaterat höga naturvärden. Många artobservationer återfinns precis utanför naturreservatens gränser vilket kan tyda på att höga naturvärden förekommer även där. Vidare studier kring buffertzoner och dess påverkan på signalarter uppmuntras.

The warming of our planet is a direct consequence of anthropogenic emissions with carbon dioxide as the main driver. A need to mitigate carbon emissions is urgent and forests can be a part of the solution since they sequester and stock carbon during their lifetime This study has shown that production forests can sequester carbon to a higher degree since they consist of younger trees which are better at sequestration than older trees. But the study also show that older forests keep sequestering carbon and might not be carbon neutral as previously thought. Old growth forests contain higher carbon stocks than younger production forests since they often remain unmanaged and can continuously accumulate carbon into living and dead biomass as well as the soil. Production forests also accumulate carbon, but it is not nearly the same amount as in old growth forests. With regard to meeting the 1,5-degree goal set by the IPCC, i.e., cutting emissions with half until 2030 and having net zero carbon dioxide emissions until 2050. Harvesting with clear-cutting was found to be worse compared with harvesting at a lower frequency which causes less emissions but still supplies wood products to the industry. The result also show that we must protect more old growth and unmanaged forests that can sequester and stock carbon longer to be able to succeed with the 1,5-degree goal. The debate climate in Sweden is heated and opinions often differ. The difference may depend on the time frame or how results are interpretated.

Abstract Boreal and arctic plant communities are responding to anthropogenic climate change that has been exceptionally rapid during the recent decades. General responses include increased productivity, range expansions and biodiversity changes, all of which affect ecosystem functions. Vegetation dynamics are however controlled by multiple drivers, and the outcomes under the changing climate are not yet fully clear. As high latitude areas often lack long-term monitoring of vegetation, alternative methods are required to observe and understand vegetation changes and dynamics. Recently, resurveying historical vegetation data has become a valuable method of studying vegetation changes over the past few decades. In this thesis, I studied multidecadal (23–60 years) vegetation changes in forest and treeless heath and tundra plant communities along a latitudinal gradient in northern Fennoscandia using both vegetation resurveys and long-term experimental data. In addition to examining climate-driven vegetation changes, I related changes in plant communities to key local drivers of each context including mesotopography, grazing, soil moisture and soil fertility. General trends among the resurveyed treeless heath sites were the pronounced increase of the dwarf shrub Empetrum nigrum ssp. hermaphroditum in snow-protected habitats and the decrease of lichens throughout. Southernmost heath communities showed strong responses to multidriver effects and had shifted towards new community states. The long-term experiment in the tundra confirmed that depending on driver combinations, tundra communities evolve towards divergent alternative states, highlighting the importance of local drivers in modifying tundra vegetation over time. Communities in fertile forest sites experienced greater temporal turnover compared to infertile forest sites, suggesting that the soil fertility level is a key predictor of vegetation changes under climate change. This particularly important finding previously relied mainly on experimental evidence. Despite these generalities, changes in diversity, plant groups and species varied under a rather uniform climatic warming trend and were often habitat- or region-specific. Thus, the results of my thesis highly motivate continued monitoring and resurveying of vegetation under rapid environmental change and also form baseline time-series data for future studies. / Tiivistelmä Poikkeuksellisen nopea ilmastonmuutos on johtanut viime vuosikymmenten aikana muutoksiin boreaalisissa ja arktisissa kasviyhteisöissä. Muutoksiin lukeutuvat tuottavuuden lisääntyminen, levinneisyysrajojen siirtyminen sekä muutokset biodiversiteetissä, mitkä kaikki muuttavat ekosysteemien toimintaa. Kasvillisuuden dynamiikkaa säätelevät kuitenkin useat paikallistason tekijät, minkä seurauksena ei ole täysin selvää, miten kasvillisuus on eri alueilla ja habitaateissa muuttunut. Koska kasvillisuuden jatkuva monitorointi on harvinaista pohjoisilla alueilla, vanhojen kasvillisuusaineistojen uudelleenkartoituksista on tullut tärkeä menetelmä muutosten havaitsemiseksi. Tutkin väitöskirjassani vuosikymmenten kuluessa tapahtuneita (23–60 vuotta) kasvillisuusmuutoksia Pohjois-Fennoskandian metsissä, puuttomilla kankailla ja tundralla uudelleenkartoitusten ja kokeellisen tutkimuksen avulla, ja kytkin ne ilmastonmuutokseen sekä tärkeimpiin paikallisiin tekijöihin. Yleisiä trendejä uudelleenkartoitetuilla puuttomilla kankailla olivat variksenmarjan (Empetrum nigrum ssp. hermaphroditum) voimakas lisääntyminen lumensuojaisissa habitaateissa sekä jäkälien väheneminen kaikkialla. Yhteisöjen kokonaismuutos oli voimakkainta eteläisillä puuttomilla kankailla, jossa se korreloi yhtä aikaa lisääntyneiden lämpötilojen ja laidunpaineen kanssa. Kokeellinen tutkimus tundralla osoitti, että kasviyhteisöt kehittyvät hyvin erilaisiksi paikallisten tekijöiden voimakkuussuhteista riippuen, jotka voivat joko hidastaa tai nopeuttaa ympäristömuutoksista johtuvia kasvillisuusmuutoksia. Metsien uudelleenkartoitus osoitti yhteisöjen kokonaismuutoksen olevan pitkällä aikavälillä suurempaa tuottavilla maaperillä lehtometsissä verrattuna karumpiin kangasmetsiin. Tutkimuksen mukaan maaperän tuottavuus on avaintekijä, joka ennustaa kasvillisuusmuutosten voimakkuutta ilmastonmuutoksen aikana. Tästä tärkeästä löydöstä oli aiemmin pääasiassa vain kokeellista tutkimustietoa. Yleisistä trendeistä huolimatta, muutokset diversiteetissä, kasviryhmissä ja yksittäisissä lajeissa olivat kuitenkin vaihtelevia ja usein habitaatti- tai aluesidonnaisia. Väitöskirjani tulokset, jotka muodostavat myös aikasarjan tuleville tutkimuksille, osoittavat kasvillisuuden monitoroinnin ja uudelleenkartoitusten olevan ensisijaisen tärkeitä, jotta kasvillisuuden dynamiikkaa voidaan ymmärtää paremmin nopeasti muuttuvissa olosuhteissa.