The occurrence of alien plant species in field margins in Finland

The results suggest that alien plant species comprise an important part of the biodiversity of Finnish field margins and semi-natural agricultural habitats. The role of field margins as dispersal corridors for invasive alien plants is limited for certain species

Weed occurrence in Finnish coastal regions: a survey of organically cropped spring cereals

Weed communities of organically cropped spring cereal stands in the southern and the northwestern coastal regions of Finland (= south and northwest, respectively) were compared with respect to number of species, frequency of occurrence, density and dry weight. Regional specialization of agricultural production along with differences in climate and soil properties were expected to generate differences in weed communities between south and northwest. Total and average numbers of species were higher in the south than in the northwest (33 vs. 26 and 15.6 vs. 10.0, respectively). Some rare species (e.g. Papaver dubium) were found in the south. Fumaria officinalis and Lamium spp. were found only in the south. The densities and dry weights of Lapsana communis, Myosotis arvensis, Polygonum aviculare, Tripleurospermum inodorum and Vicia spp. were higher in the south, while the densities and dry weights of Elymus repens, Persicaria spp. and Spergula arvensis were higher in the northwest. Total density of weeds did not differ between south and northwest (average = 565 vs. 570 shoots m-2, respectively). Total dry weight of weeds was higher in the northwest compared with the south (average = 1594 vs. 697 kg ha-1, respectively), mainly due to the high dry weight of E. repens. The only variable that was dependent on the duration of organic farming was weed density in the south. The abundance of nitrophilous in relation to non-nitrophilous weed species was higher while the abundance of perennial ruderal and grassland weed species was lower compared with previous weed surveys. This can be regarded as the result of increasing cropping intensity on organic farms in Finland. Different weed communities call for the application of specific target-oriented weed management in the respective coastal regions

Weed flora and weed management of field peas in Finland

The composition of the weed flora of dry pea (Pisum sativum L.) fields and cropping practices were investigated in southwestern Finland. Surveys were done in 2002–2003 in 119 conventionally cropped fields and 64 fields under organic cropping. Herbicides were applied to 92% of conventionally cropped fields where they provided relatively good control but were costly. Weeds were controlled mechanically only in five fields under organic production. A total of 76 weed species were recorded, of which 29 exceeded the 10% frequency level of occurrence. The average number of weed species per field was 10 under conventional cropping and 18 under organic cropping. The most frequent weed species in both cropping practices were Chenopodium album, Stellaria media and Viola arvensis. Elymus repens was the most frequent grass species. The difference in species composition under conventional and organic cropping was detected with Redundancy Analysis. Under conventional cropping, features of crop stand and weed control explained 38.7% and 37.6% of the variation respectively. Under organic cropping the age of crop stand and field location (y co-ordinate) respectively explained best the variation. Weeds could be efficiently managed with herbicides under conventional cropping, but they represented a significant problem for organic production. Mixed cultivation of pea with cereals is recommended, particularly for organic cropping, as it favours crop competition against weeds

The change in the distribution of arable weeds in Europe as a consequence of climate change

This study aimed at exploring the future distribution of 25 weeed species, representing different distribution patterns and taxa, at European scale. Using generalized additive models, and data on current climate and species distributions and two different climate scenarios for the period 2051-2080, we developed predictions of the currently suitable area and potential range size changes of 25 European weed species

Ontology of technology : Mobile technology in the Kathmandu valley

In contemporary times, modern communication technologies connect enormous amounts of different people from different cultures together. Yet, for all these different people to be able to utilize these technologies requires that they also share some kind a common understanding of them. Consequently, the purpose of this thesis is to study how a shared understanding of a technology is constructed and maintained among people who might otherwise have very different worldviews. It answers to this question through an ethnographic fieldwork which focuses on how the culturally very heterogeneous people of the Kathmandu valley are unified through mobile technology into a connected communication network. To analyse how the common understanding of mobile technology is achieved it conducts a comparison. It compares mobile technology to other different methods of establishing social unity in the Kathmandu valley described by anthropological studies of its cultural forms. By contrasting and comparing these different practices it elicits how the construction of a common understanding concerning mobile technology requires some ontological presuppositions concerning reality in general. Yet, analysis of the presupposed truths that are used to establish technological unity raises a theoretical and methodological problem. This problem is that the ontological truths concerning reality that connect the users of mobile technology together are similar to those which are often used as the basis of social scientific research. To solve this problem this thesis utilizes a method of science and technology studies known as actor-network theory. Consequently, by utilizing actor-network theory it constructs a method which enables to give an ontological description of mobile technology

What was behind the bark? : An assessment of decay among urban Tilia, Betula and Acer trees felled as hazardous in the Helsinki City area

Old trees growing in urban environments are often felled due to symptoms of mechanical defects that could be hazardous to people and property. The decisions concerning these removals are justified by risk assessments carried out by tree care professionals. The major motivation for this study was to determine the most common profiles of potential hazard characteristics for the three most common urban tree genera in Helsinki City: Tilia, Betula and Acer, and in this way improve management practices and protection of old amenity trees. For this research, material from approximately 250 urban trees was collected in cooperation with the City of Helsinki Public Works Department during 2001 - 2004. From the total number of trees sampled, approximately 70% were defined as hazardous. The tree species had characteristic features as potential hazard profiles. For Tilia trees, hollowed heartwood with low fungal activity and advanced decay caused by Ganoderma lipsiense were the two most common profiles. In Betula spp., the primary reason for tree removal was usually lowered amenity value in terms of decline of the crown. Internal cracks, most often due to weak fork formation, were common causes of potential failure in Acer spp. Decay caused by Rigidoporus populinus often increased the risk of stem breakage in these Acer trees. Of the decay fungi observed, G. lipsiense was most often the reason for the increased risk of stem collapse. Other fungi that also caused extensive decay were R. populinus, Inonotus obliquus, Kretzschmaria deusta and Phellinus igniarius. The most common decay fungi in terms of incidence were Pholiota spp., but decay caused by these species did not have a high potential for causing stem breakage, because it rarely extended to the cambium. The various evaluations used in the study suggested contradictions in felling decisions based on trees displaying different stages of decay. For protection of old urban trees, it is crucial to develop monitoring methods so that tree care professionals could better analyse the rate of decay progression towards the sapwood and separate those trees with decreasing amounts of sound wood from those with decay that is restricted to the heartwood area.Kaupunkipuita joudutaan kaatamaan lahon ja mekaanisten vikojen aiheuttaman riskin vuoksi. Kaatopäätökset tehdään puunhoidon ammattilaisten tekemien kuntoselvitysten perusteella. Tämän tutkimuksen tarkoituksena oli selvittää yleisimpien kaupunkipuulajien (lehmus, koivu, vaahtera) tavallisimmat vaurioprofiilit, ja tällä tavoin parantaa puiden kuntoarviointia ja vanhojen kaupunkipuiden suojelumahdollisuuksia. Tutkimusta varten kerättiin, yhteistyössä Helsingin kaupungin rakennusviraston kanssa, noin 250 puun tutkimusmateriaali. Näistä puista n. 70% oli kuntotutkimuksessa todettu vaarallisiksi. Vaurioprofiilit vaihtelivat puulajin mukaan. Lehmuksella suurimman riskin aiheuttivat lattakäävän laho ja runkojen pitkälle edennyt onkaloituminen. Koivulle tyypillistä oli puun yleinen ränsistyminen. Vaahteralla suurimman riskin aiheutti isojen oksien ja haarojen repeämisvaara. Tämä johtui ensisijaisesti heikoista haaraliitoksista, mutta usein repeämisriskiä lisäsi haaraliitoksesta alkunsa saanut vaahterankäävän laho. Tutkituista lahottajasienilajeista suurimman rungon katkeamisriskin aiheutti lattakäävän laho. Muita haitallisia lahottajia olivat vaahterankääpä, pakurikääpä, karstasyylä ja arinakääpä. Helokka-lajeja eristettiin tutkimusmateriaalista kaikkein runsaimmin, mutta näiden lajien laho ei yleensä aiheuttanut suurta riskiä rungon katkeamiselle, koska laho pysytteli sydänpuun alueella. Tutkimusmateriaali osoitti, että vanhojen puiden suojelua voitaisiin parantaa kiinnittämällä enemmän huomiota lahoprosessin seurantaan. Varsinkin onkaloituneiden puiden osalta tulisi pyrkiä tunnistamaan puut, joissa puun puolustusmekanismit ovat onnistuneesti rajanneet lahon leviämisen sydänpuun alueelle. Tämä on tärkeää siksi, että onkaloituneet puut ovat ekologisesti tärkeitä. Ne tarjoavat hitaasti kehittyvän ekologisen lokeron monille eliölajeille