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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.
21

Har signalarter störst förekomst inom eller utanför Dalarnas boreala naturreservat? : En studie om arttätheten av signalarter i Dalarnas barrskogar / Are signal species most abundant inside-or outside the boreal nature reserves? : A study about the density of indicator species in the coniferous forests in Dalarna, Sweden

Ahlgren, Caroline January 2023 (has links)
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.
22

Brukningshistorik i Jämtlands kalkbarrskogar : En studie baserad på GIS-analys av kartor / The historical land-use of Calcareous Coniferous Forests in Jämtland : A study based on GIS analysis of maps

Johansson Schleu, Nora January 2022 (has links)
Kalkbarrskogar är en sällsynt och artrik skogstyp i Sverige. Stora arealer finns i Jämtland. Skogstypen kalkbarrskog är prioriterade för områdesskydd och det finns därför ett behov att undersöka den. Studien genomfördes i samarbete med Länsstyrelsen i Jämtland. 45 prioritetsobjekt undersöktes genom GIS-baserade analyser. Målet var att undersöka objektens brukningshistorik för att undersöka eventuell påverkan på naturvärdena. Syftet var att utreda behovet av formellt områdesskydd. Samtliga objekt har fram till nutid aldrig blivit kalavverkade. 80 % var historiskt brukade med skogsbete och virkesuttag, vilket kan ha hållit skogarna glesa fram till 1960-talet. Studien kan inte visa om brukningshistoriken påverkat dagens naturvärden. Naturvärdena kan funnits innan brukandet startat, samt att andra miljöparametrar kan haft större betydelse. Idag är en femtedel av objekten helt eller delvis avverkade och en fjärdedel avverkningsanmälda. Studien kan styrka behovet av formellt områdesskydd på kalkbarrskogar i Jämtland eftersom det är ett motiverat alternativ för att naturvärdena bibehålls.
23

Determinantes da variação geográfica da biomassa flo restal no sul do Brasil: a contribuição de Floresta com Araucária

Rosenfield, Milena Fermina 21 February 2011 (has links)
Submitted by Mariana Dornelles Vargas (marianadv) on 2015-03-26T14:22:21Z No. of bitstreams: 1 determinantes_variacao.pdf: 908319 bytes, checksum: 62b3232a58e65bb0e1abb6ef44b5c2bc (MD5) / Made available in DSpace on 2015-03-26T14:22:21Z (GMT). No. of bitstreams: 1 determinantes_variacao.pdf: 908319 bytes, checksum: 62b3232a58e65bb0e1abb6ef44b5c2bc (MD5) Previous issue date: 2011-02-21 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Uma variedade de fatores ambientais e bióticos afeta a produtividade florestal e determina o acúmulo de biomassa. Em ecossistemas florestais, o aumento da produtividade primária propicia o aumento da biomassa vegetal e consequentemente o aumento do carbono orgânico estocado. Dentre os fatores que influenciam a produção de biomassa, podemos citar temperatura, pluviosidade, tipo de solo, composição florística e regime de distúrbios. Nesse sentido, há o consenso entre pesquisadores de que o aumento da temperatura, a homogeneidade do regime de chuvas e solos férteis aumentam a produtividade e possibilitam um maior acúmulo de biomassa. Além disso, diversos autores propõem que riqueza e diversidade de espécies teriam efeito positivo sobre a biomassa, pois aumentariam a eficiência no uso dos recursos. Os objetivos deste estudo foram avaliar as variáveis que afetam a biomassa florestal viva acima do solo (BAS) na região subtropical do sul do Brasil, além de analisar a distribuição espacial das estimativas de biomassa em escala regional. O estudo foi realizado em Florestas Subtropicais Úmidas do sul do Brasil, classificadas como Florestas Latifoliadas (FL) e Florestas Mistas de Coníferas e Latifoliadas (FM). Um total de 38 parcelas de 1 ha foram selecionadas e todas as árvores com DAP ≥ 9,5 cm foram incluídas para as estimativas de biomassa. Valores de BAS foram obtidos utilizando equações alométricas já publicadas na literatura. As variáveis ambientais (altitude, precipitação, temperatura e tipo de solo) foram obtidas da literatura e as variáveis bióticas (densidade e diversidade) foram calculadas a partir da base de dados. Para o conjunto total de dados, a BAS média foi de 194,3 ± 116,8 Mg ha-1 (média ± DP) e a densidade média de carbono foi de 97,2 ± 58,4 MgC ha-1. As estimativas entre tipos florestais diferiram entre si (t= -4,598; p<0,001): a BAS média foi inferior em FL (AGBFL = 118,0 ± 58,4 Mg ha-1) quando comparada a FM (AGBFM = 249,8 ± 118,1 Mg ha-1). A análise de componentes principais executou de forma satisfatória a redução da base de dados de clima e de solo. A regressão múltipla explanatória explicou 49,8% da variação na BAS (Ylog biomassa = 0,03(0,49)xraiz densidade + 0,11(0,36)x eixo latitudinal - 0,22(-0,85)xeixo altitudinal - 0,03(-0,36)xdiversidade - 0,09(-0,35)xeixo matéria orgânica + 1,66; F5,32=8,34; p<0,001; r2=0,498). A altitude contribuiu mais para o modelo do que qualquer outra variável. Não foi encontrada dependência espacial entre as parcelas. Os resultados do nosso estudo mostram uma relação negativa entre biomassa acima do solo e altitude. Assim, valores elevados de BAS estão localizados em altitudes mais elevadas e sujeitos a temperaturas amenas e frequentes chuvas mensais. Parece haver uma contribuição importante da conífera Araucaria angustifolia nas parcelas de FM, visto que árvores de grande porte da espécie foram encontradas em inúmeras unidades amostrais. Florestas subtropicais parecem ser de grande interesse para o sequestro de carbono, especialmente em áreas de Florestas Mistas. No Brasil, a espécie de conífera ameaçada de extinção A. angustifolia compõe florestas com alta diversidade (Florestas com Araucária), com grande potencial de acúmulo de biomassa e sequestro de carbono, enfocando ainda mais a importância de conservação deste ecossistema. / A variety of environmental and biotic factors affect forest productivity and determines biomass accumulation. In forest ecosystems, the increase in primary productivity results in an increase in plant biomass and consequently elevates storage of organic carbon. Among the factors that influence biomass production, we should mention temperature, rainfall, soil type, floristic composition and disturbance regimes. It is widely accepted among researchers that increasing temperature, rainfall homogeneity and fertile soils increase productivity and enable higher biomass accumulation. Moreover, many authors indicate that species richness and diversity have a positive effect on biomass, because of the higher efficiency on resource use. The objectives of the study were to evaluate the variables affecting live aboveground forest biomass (AGB) in Subtropical Southern Brazil and analyze the spatial distribution of biomass estimates. The study was performed in Subtropical Moist Forests of Southern Brazil, classified as Broadleaf Forests (BF) and Mixed Coniferous-Broadleaf Forests (MF). A total of 38 1-ha plots were selected and all trees with DBH ≥ 9.5 cm were included for biomass estimation. Values for AGB were obtained using published alometric equations. Environmental variables (elevation, rainfall, temperature and soils) were obtained from the literature and biotic variables (density and diversity) were calculated from the data set. For the total number of plots, mean AGB was 194.3 ± 116.8 Mg ha-1 (mean ± SD) and mean carbon density 97.2 ± 58.4 MgC ha-1. Estimates differed between forest types (t= -4.598; p<0.001): mean AGB was lower in BF (AGBBF = 118.0 ± 58.4 Mg ha-1) when compared to MF (AGBMF = 249.8 ± 118.1 Mg ha-1). Principal component analysis performed well in summarizing climate and soil data sets. The explanatory multiple regression explained 49.8% of the variation in AGB (Ylog biomass = 0.03(0.49)xsqroot density + 0.11(0.36)x latitudinal axis - 0.22(-0.85)xelevation axis ? 0.03(-0.36)xdiversity - 0.09(-0.35)xorganic matter axis + 1.66; F5,32=8.34, p<0.001; r2=0.498). Elevation contributed more to the model than any other variable. There was no spatial dependency found between plots. The results from our study showed a negative relationship between aboveground biomass and elevation. Therefore, higher values of AGB are located at higher altitudes and subjected to cooler temperatures and frequent monthly rainfall. There seems to be an important contribution of the coniferous species Araucaria angustifolia in MF plots, since large trees of this species were found in many of the samples. Subtropical forests appear to be of great interest for carbon sequestration, especially in areas of Mixed Coniferous-Broadleaf Forests. In Brazil, the endangered coniferous species A. angustifolia is part of a high diversity forest (Araucaria Forest), with great potential for biomass accumulation and carbon sequestration, emphasizing the importance in conserving this ecosystem.
24

Describing Snowpacks in Arizona Mixed Conifer Forests with a Storage-Duration Index

Warren, Mark A., Ffolliott, Peter F. 12 April 1975 (has links)
From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / The quantification of snowpacks in relation to inventory-prediction may be useful in the development of water yield improvement practices involving vegetation management in the mixed conifer forests in Arizona. While mixed conifer forests are relatively limited in extent in Arizona, the potential for water yield improvement by manipulation of snow storage through vegetation management may be high. Sample points on the north fork of Thomas Creek showed high initial snow storage followed by slow melt in association with low forest densities, low potential insolation values, and high elevation. Sample points exhibiting these conditions also possessed maximum storage-duration index values. Low initial snow storage followed by rapid melt was associated with high forest densities, high potential insolation values, and low elevations
25

Interakce mikroskopických hub a krytenek v opadu smrku ztepilého / Interactions of microscopic fungi and testate amoebae in Norway spruce litter

Konvalinková, Tereza January 2011 (has links)
Both testate amoebae and fungi are common inhabitants of coniferous litter. Their interactions in this environment were rarely studied, although they reach high biodiversity and can play a significant role in nutrient cycling in this environment. In this study, a cultivation of litter needles in the damp chambers was used to investigate interactions between fungi and testate amoebae. Observation of spruce litter needles in environmental scanning electron microscope was used to better characterize testate amoebae communities directly on the needles. Additionally, two experiments changing the biotic conditions in the microcosm were used to follow a principle of the interactions. Three species of testate amoebae from litter needles were able to colonize the filter paper on the bottom of the damp chambers. Occurrence of Phryganella acropodia and Assulina muscorum on the filter paper was significantly fuelled by the presence of mycelium. Assulina muscorum was associated with the fungal spores and Arcella discoides was attracted by sporulating colonies of Cladosporium spp. in the damp chambers. By contrast, no association of putatively mycophagous Phryganella acropodia with fungal spores was observed. Arcella discoides was attracted both by live and death mycelium in additional experiment. Interestingly, the...
26

The diversity of fungi in coniferous forests and mixed forests / Svampars diversitet i barr- och blandskog

Asplund, Ida January 2023 (has links)
The fungal domain has one of the highest biodiversities among eukaryotes and species within the domain fill important ecological roles, such as mutualistic mycorrhiza, decomposers, parasites and pathogens. The development of forest ecosystems and their related processes has not only been linked to fungal diversity but the composition and abundance of fungi benefits the abundance and diversity of other species as well. In this study three questions concerning the differences in the fungal communities between mixed forests and coniferous forests were considered. Inventories were done in coniferous forest and mixed forest areas classified as nature reserves and later statistically analyzed. The study could show that while the probability of finding ectomycorrhiza was significantly higher in mixed forests than coniferous forests, the probability of finding saprotrophs was significantly higher in coniferous forests than in mixed forests. Results in contrast to other studies were also found. The study revealed that more is needed to be done on the topic of forest fungi in mixed forest and coniferous forest areas. / Svampdomänen har en av de högsta biologiska mångfalderna bland eukaryoter och domänens arter innehar viktiga ekologiska roller, såsom mutualistisk mykorrhiza, nedbrytare, parasiter och patogener. Utvecklingen av skogsekosystem och deras relaterade processer har inte bara kopplats till svampdiversitet utan svamparnas sammansättning och förekomst gynnar också förekomst av och mångfald hos andra arter. I denna studie behandlades tre frågor om skillnaderna i svampsamhällen mellan blandskogar och barrskogar. Inventeringar gjordes i barrskogs- och blandskogsområden klassificerade som naturreservat och analyserades senare statistiskt. Studien kunde visa att även om sannolikheten för att hitta ektomykorrhiza var signifikant högre i blandskogar än barrskogar, var sannolikheten för att hitta saprotrofer signifikant högre i barrskogar än i blandskogar. Resultat i motsats till andra studier hittades också. Studien visade att det behövs mer forskning om skogssvampar i blandskog och barrskogsområden.
27

Jämförelse av observationer av naturvårdsarter mellan skyddade värdekärnor och produktionsskogar i Dalarna, Sverige / Comparing observations of conservation species between protected high conservation value forests and production forests in Dalarna, Sweden

Jansson, Linn January 2024 (has links)
Biologisk mångfald minskar kraftigt i hela världen som ett resultat av mänskliga handlingar. Den biologiska mångfalden hos svenska boreala skogar hotas av det moderna skogsbruket där trakthyggesbruk som är en vanlig skogsbruksmetod skapar en miljö som är svår att överleva i för naturvårdsarter. I denna studie är syftet att undersöka om observationer av sex stycken naturvårdsarter är högre i skyddade värdekärnor bestående av gammal barrskog än i produktionsbarrskog i Dalarnas län, Sverige. Detta genom att analysera andelen av de totala observationerna i proportion till andelen av den totala arealen för respektive skogstyp samt andelen observationer av varje naturvårdsart för sig i proportion till andelen av den totala arealen för respektive skogstyp. Då tidigare studier visat att artantalet och den biologiska mångfalden är högre i skyddade områden, inkluderat gammal skog, förväntades det att resultatet för denna studie skulle följa samma trend. Rumsliga data för skyddade värdekärnor och produktionsskog erhålls från Naturvårdsverket, Skogskarta från Sveriges lantbruksuniversitet (SLU) och rumsliga data för artobservationer från SLU Artdatabanken. Den rumsliga analysen utfördes i QGIS och en statistisk analys genom ett Pearson Chi square-test i SPSS. Resultatet i studien visade att det inte finns en signifikant skillnad i proportionen mellan andelen observationer och andelen areal för respektive skogstyp vilket är skyddade värdekärnor och produktionsskog. För varje enskild naturvårdsart var det endast för rynkskinn (Phlebia centrifuga) som det fanns en signifikant skillnad i proportionen mellan andelen observationer och andelen areal för respektive skogstyp vilket indikerar på att den arten föredrar skyddade värdekärnor över produktionsskogar. Studiens resultat överensstämmer inte med tidigare studier men trots detta är bevarandet och främjandet av gamla skogar som är skyddade en viktig del i arbetet mot att stoppa minskningen av den biologiska mångfalden. / Biodiversity is declining rapidly worldwide as a result of human actions. The biodiversity of Swedish boreal forests is threatened by modern forestry, where clearfelling, which is a common forestry practice, creates an environment that is difficult for conservation species to survive in. In this study, the aim is to investigate whether observations of six conservation species are higher in protected high conservation value forests consisting of old coniferous forest than in production coniferous forest in Dalarna County, Sweden. This by analyzing the share of total observations in proportion to the share of the total area for each forest type, and also the share of observations of each conservation species separately in proportion to the share of the total area for each forest type. As previous studies have shown that species numbers and biodiversity are higher in protected areas including old-growth forests, it was expected that the results of this study would follow the same trend. Spatial data for protected high conservation value forests and production forests were obtained from the Swedish Environmental Protection Agency, Forest Map from the Swedish University of Agricultural Sciences (SLU) and spatial data for species observations from the SLU Swedish Species Information Centre. The spatial analysis was performed in QGIS and a statistical analysis through a Pearson Chi square test in SPSS. The results of the study showed that there is no significant difference in the proportion of observations to area for each forest type that is protected high conservation value forests and production forests. For each individual conservation species, only for Phlebia centrifuga fungus was there a significant difference in the proportion between the share of observations and the share of area for each forest type which indicates that this species prefers high conservation value forests over production forests. The results of the study are not consistent with previous studies, but despite this the conservation and promotion of protected old-growth forests is an important part of efforts to halt biodiversity loss.
28

Probability Distributions of Snow Course Data for Central Arizona

Carv, Lawrence E., Beschta, Robert L. 05 May 1973 (has links)
From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / A preliminary study of probability distributions for use on snowpack accumulation in the central Arizona highlands was made from 22 snow courses selected as having 10 or more years of available records. Due to the frequent occurrence of zero water equivalent value, application of a single continuous probability distribution is precluded. By means of two distributions, however, the snowpack water equivalent can be assessed by a binomial distribution describing the probability of snow, and a lognormal distribution describing the probability of water equivalent. The area chosen for detailed analysis is where the headwaters of many of Arizona's major river systems occur.

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