• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 3
  • 3
  • 1
  • Tagged with
  • 13
  • 13
  • 13
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 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.
11

Evertebraters kolonisation på fin ved i semi-naturliga bäckar / Colonization of invertebrates on fine wood in semi-natural streams

Johansson, Patricia January 2015 (has links)
Wood can be added to streams to create microhabitats that provide macroinvertebrates with an opportunity for re-colonization by making the stream more heterogeneous. I examined colonization on wood substrate by macroinvertebrates in semi-natural streams in northern Finland during a three month period. Each of the streams was divided in three sections A, B and C, half of which were provided with wood. The focus has been on whether the density of macroinvertebrates changes with time, along an upstream-downstream direction in the streams, or in streams with two wood sections if macroinvertebrates will colonize the first section with wood that they come in contact with (upstream section) or if they continue downstream to the second section with wood. Wood from Salix sp. was placed in nine of the 18 enclosures during mid-June. Samples of wood were removed from the streams on three different occasions from August to October 2014. A total of 32 taxa were identified from the wood and assigned to functional feeding groups: shredders, scrapers, active filter feeders, passive filter feeders, collectors, miners, piercers and predators. The results showed that collectors, miners and piercers increased in density during the month of October and the abundance of scrapers was higher in the upstream location than in the downstream location. Total number of macroinvertebrates, collectors, passive filter feeders and predators had a higher colonization on the first substrate they came into contact with. / Ved i homogena vattendrag skapar mikrohabitat och ger evertebrater en möjlighet att återkolonisera vattendraget genom att göra vattendraget mer heterogent. Jag har undersökt makroevertebraters kolonisation på ved i semi-naturliga bäckar under en tre månaders-period i norra Finland. Bäckarna var uppdelade i tre sektioner upp-, mellan- och nedströms respektive A, B och C. Av 18 sektioner var nio ved försedda. Jag har fokuserat på om tätheten av evertebrater och diversiteten förändras med tiden, längs bäckarna dvs. uppströms – nedströms, och om makroevertebrater kommer kolonisera den första vedförsedda sektionen de kommer i kontakt med eller fortsätta till den efterföljande vedförsedda sektionen. Ved från Salix sp. placerades i nio inhägnader i mitten på juni. Prov på ved togs vid tre olika tidpunkter under studieperioden från Augusti till Oktober 2014. En totala av 32 taxa identifierades från veden och grupperades i funktionella födogrupper: Sönderdelare, skrapare, aktiva filtrerare, passiva filtrerare, samlare, växtgrävare, växtsugare och predatorer. Resultatet visade att samlare, växtgrävare och växtsugare ökade i täthet under oktober månad samt att skapare föredrog ett uppströmsläge framför de andra två möjligheterna. Totala antalet evertebrater, samlare, passiva filtrerare och predatorer koloniserade det första substratet de kom i kontakt med i större utsträckning än de andra födogrupperna.
12

Palaeoekologie interakcí rostlin a členovců ze spodního miocénu mostecké pánve v severních Čechách / Palaeocology of plant-arthropod associations from the Lower Miocene of the Most Basin in northern Bohemia (Czech Republic)

Knor, Stanislav January 2010 (has links)
Terrestrial plants and insects account for the majority of the Earth's biodiversity today, and almost half of all insect species are herbivores. Thus, insects and plants share ancient associations date back for more than 400 million years. However, investigation of their interactions stands largely at the beginning in Western Europe. Nearly 4300 plant remains showing various kinds of feeding damages are available for the present study. These trace fossils are classified as so-called functional feeding-groups supply an outstanding example of the complexity, the structure and the changes of terrestrial ecosystems, are not well known during this interval. In Europe, the Neogene is characterized by palaeogeographic re- organization due to the collision of the African with the Eurasian plates. The Neogene plant record in Europe is rich and diverse offering a profound large-scale understanding of the floristic and vegetational development. A database of fossil traces from the Most Basin was compiled and analyzed by various statistical methods in terms of the diversity and intensity of palaeo-herbivory. The primary objective is to present results on the development of insect herbivory through the section of the Bílina Mine in North Bohemia, with the aim of understanding principal factors that caused the...
13

Correlation of Watershed NDVI Values to Benthic Macroinvertebrate Biodiversity in Eight North American Wadeable Streams

Gallagher, Denice Lynne 05 1900 (has links)
Water quality of a stream or river is influenced by the surrounding landscape and vegetation. The Normalized Difference Vegetation Index (NDVI) is commonly used to characterize landcover and vegetation density. Benthic macroinvertebrates are ubiquitous in freshwater streams and are excellent indicators of the quality of freshwater habitats. Data from one NDVI remote sensing flight and one macroinvertebrate sampling event for eight wadeable stream study sites in the National Ecological Observatory Network (NEON) were acquired. Proportions of high, moderate, and sparse vegetation were calculated for each stream watershed using ArcGIS. Functional feeding groups and tolerance values were assigned to macroinvertebrate taxa. The Fourth-corner and RLQ methods of analysis, available in the ade4 package for R software, were used to evaluate the relationships of macroinvertebrate traits with environmental variables. Hypothesis testing using Model 6 in the ade4 package resulted in p-values of 0.066 and 0.057 for global (overall) significance. Mean NDVI values of moderately vegetated areas and proportion of sparse vegetation were found to be significant to percent shredders at alpha ≤ 0.05. Results of these methods of analysis, when combined with traditional macroinvertebrate sampling metrics, show that NDVI can be a useful, additional tool to characterize a watershed and its effects on macroinvertebrate community composition and structure.

Page generated in 0.1401 seconds