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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Hur har sandstäppsarealen på Öland förändrats mellan 1995 och 2009 och var finns möjliga restaureringsytor

Lundquist, Jonas January 2009 (has links)
Xeric sand calcareous grasslands or sand steppe is a rare habitat type in Sweden. In our country the occurrence of sand steppe is limited to eastern Scania and a few sites on the Baltic island of Öland. The availability of calcareous sand and a continuous management of the soil surface regulate formation of the sand steppe. A low annual precipitation is also a critical factor. Due to these unique circumstances the habitat type has never had a great distribution in the country. Sand steppe is closely related to the agricultural landscape with a long tradition of extensive arable farming and grazing animals. Patches of bare sand mixed with a sparse cover of low grass vegetation is the characteristic of the habitat. Changes in land use linked to agricultural modernization, and pine-tree plantations in former sand steppe areas, have made the habitat seriously threatened today. The purpose of the survey has been to carry out a detailed mapping of sand steppe on Öland and to study how the habitat changed over the last fourteen years. I wanted to see what such a change analysis could say about the future of the sand steppe on Öland where the assumption was that the habitat is reduced and the overgrowth is inevitable without restoration measures. As with other similar types of culture-guided grasslands the sand steppe habitat is never in a stable equilibrium. Without disturbance of the topsoil layer, grazing animals or human activity the sand steppe will get overgrown. By using the land for cultivation the process of succession is delayed. This process can be illustrated by the three development phases associated with sand steppe, the initial phase (1st class), the optimal phase (2nd class), and the phase of degradation (3rd class). Both the lack of management practices and improper land use is a threat to the habitat. A number of rare and red-listed plant species are associated with the habitat together with the indicator species, Koeleria glauca. Sand steppe is also a very important habitat for insects, order Hymenoptera and order Coleoptera. The current situation of sand steppe on Öland consists of 15 sites all of which can be found on the east side of the island, along the ancient shorelines from the early stages in the development of the Baltic Sea. The sites have been carefully mapped by counting the number of individuals of Koeleria glauca and by the quantification of the three phases of development for each site. The number of Koeleria glauca individuals on Öland (July 2009), is 604 805. A change analysis was carried out to compare the distribution of sand steppe on Öland in 1995 with the distribution in 2009. Because of incomplete data in the 1995 inventory, the result of the analysis is considered to be a trend. The total area of sand steppe on Öland has increased, from 36.5 to 41.5 hectares since the 1995 inventory. This is contrary to the hypothesis that the area of sand steppe had declined. The reason to this total increase is probably due to greater awareness of the habitat sites. The distribution of development phases shows a clear dominance of the 3rd class-surfaces. The reason for such a large increase of the third phase is mainly due to an increased knowledge of the existence of Koeleria glauca at each site. But since the proportion of the initial phase and the optimal phase have been reduced this suggests that the 3.rd class-surfaces has increased at the expense of the 1.st- and 2.nd classes. This provides a future indication for the sand steppe sites on Öland where overgrowth is inevitable, without restorative management measures to create new sand steppe. The assumption that small sites get overgrown faster than large sites has been clearly confirmed. Such a fragmentation process, which also is a result of the overgrowth, is an additional threat in the longer term. At an increased habitat fragmentation risks of isolation and inbreeding might occur and finally a gradual and increasing extinction debt. Since the sand steppe environment also allows for species that have general needs of bare sand the restoration and preservation of the habitat type is of great importance. Thanks to the distinctive character of the habitat there is a large commitment among nature conservation authorities and in the final stages of this work a decision was made regarding Åby sandbackar, a prospective nature reserve on Öland.
2

Skyddsvärda kärlväxter i Haväng och Vitemölla strandbackar : – utbredning, hot och skötsel

Persson, Linnéa January 2017 (has links)
Semi-natural grasslands are one of the most threatened habitats in Scandinavia. The grassland in this study is situated in the northern part of the nature preserve of Haväng och Vitemölla strandbackar in the province of Skåne and consists of grey dunes and a pasture which partly consists of calcareous grassland and the vegetation type sand steppe which is very rare in Sweden. There are several threatened plants in the area and during the summer of 2017 their distribution was registered to be able to protect them during conservation management. The results showed that most of the area contained important species and the most important areas to protect were the sand steppe areas. This is probably due to the dry, sandy, calcareous and nutrient poor conditions in these areas which many of the threatened plants are connected to. Most of the threatened plants were found in abundance in the area but have a limited distribution in Sweden. The population of Eryngium maritimum however was very small and is threatened by extinction. The plants in the area are threatened by a long-term process of nutrient enrichment and continuous leakage of calcium which may lead to lower pH and a more nutrient rich soil which leads to a higher availability of phosphorous. This may lead to a change in species composition and loss of species richness. Continuous grazing, soil disturbance to expose lime-rich sand and also removal of litter to minimize the nutrient levels are needed to maintain favorable conditions in the area. However, the number of important species requires attention and careful planning, especially in the sand steppe areas. / Ängs-och hagmarker är några av de mest hotade och viktiga habitattyperna i Skandinavien. Gräsmarken som studerades i detta projekt ligger i norra delarna av naturreservatet Haväng och Vitemölla strandbackar i Skåne och består av gräsbevuxna sanddyner och en hage med inslag av kalkgräsmark och marktypen sandstäpp som är väldigt sällsynt i Sverige. I reservatet finns flera skyddsvärda kärlväxter och under sommaren 2017 kartlades deras utbredning för att bättre kunna skydda dem vid skötsel- och restaureringsåtgärder. Resultatet visade att större delen av området innehåller skyddsvärda arter och att de mest skyddsvärda områdena var de delar av området där det fanns inslag av sandstäpp. Detta beror med stor sannolikhet på att de flesta skyddsvärda arterna i området var knutna till de torra, sandiga, kalkhaltiga och näringsfattiga förhållanden som rådde där. De flesta skyddsvärda arter fanns i stora antal i det undersökta området men har en begränsad utbredning i Sverige. Populationen av Eryngium maritimum var dock så litet att det hotas av utrotning. I övrigt hotas växterna i området på längre sikt av ökad tillsättning av näringsämnen och långvarig urlakning av kalk. Detta kan leda till lägre pH och mer näringsrik mark och gör att den nuvarande artsammansättningen kan försvinna och ersättas. För att området ska fortsätta ha en gynnsam status kommer det krävas fortsatt bete, skapande av sandblottor för att röra upp kalkrik sand samt åtgärder så som avlägsnande av förna och ytskikt för att hålla nere näringshalten. Det stora antalet rödlistade och skyddsvärda arter i området gör dock att det krävs varsamhet och noggrann planering vid en åtgärd, framför allt i sandstäppsområdena.

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