• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 38
  • 20
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 80
  • 80
  • 21
  • 20
  • 19
  • 15
  • 14
  • 13
  • 12
  • 12
  • 12
  • 11
  • 10
  • 10
  • 10
  • 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

Factors affecting rhizosphere carbon-flow in Lolium perenne

Meharg, Andrew Alexander January 1989 (has links)
The dynamics of root carbon have been studied on a limited number of plants under a limited range of environmental conditions. This is particularly true of temperate pasture grasses. It was proposed to investigate rhizosphere carbon flow within Lolium perenne, to determine environmental factors affecting root exudation and root respiration. A number of microcosms were designed in which ryegrass could be pulse labelled with 14C-CO2, and the fate of the label determined within a plant-soil system. A wide range of factors were found to affect the distribution of carbon within the plant and soil under laboratory conditions. These factors include plant stage of development, micro-organisms, temperature, soil pH, soil water stress and soil anaerobism. A field experiment was carried out to estimate rhizosphere carbon flow under 'natural' conditions and to determine if the laboratory studies could be related to field conditions. Results showed that rhizosphere carbon flow varied greatly depending on environmental conditions. It was proposed that the major loss of newly photoassimilated carbon was dominated by root respiration rather than by root exudation. Inoculation with micro-organisms affected carbon loss from plant roots as exudates. The pattern of carbon distribution within the plant and rhizosphere varied greatly depending on the inoculant.
2

Early changes in soil under birch and heather

Ramsay, Amanda J. January 1990 (has links)
Heather plants were established, by Dr. John Miles, in gaps created in existing birch stands in 1979 at Craggan (NJ190322) and birch trees planted in heather moorland during 1977-1980 at Delnalyne (NJ189175). This study attempts to identify the processes leading to differential soil development beneath the two contrasting vegetation types over the period 1985-88 i.e. c 6 years after establishment. Field work involved the chemical analysis of soil solution and estimates of microbial biomass and basal respiration rates under birch and heather at both sites. Laboratory-based experiments were conducted to investigate the trends observed in the field. Major changes in soil processes were attributed to rapid growth and therefore nutrient uptake by the transplanted species. However, some of the changes due to birch trees, which were observed during studies of birch chronosequences by Miles &'38 Young (1980) and Miles (1981) can be attributed to high nutrient inputs in throughfall and litter under birch, which affect abiotic processes and stimulate microbial activity and nutrient transformation rates. Root inputs also influenced biological processes.
3

The survival of selected non-indigenous microorganisms in the soil ecosystem

Garriott, Charles R. January 2010 (has links)
Digitized by Kansas Correctional Industries
4

Analys av artificiella marktyper vid vatten med hjälp av GIS, Värmlands län 2007

Hansson, Pernilla, Sanfridsson, Christina January 2007 (has links)
<p>On commission of the County administrative board in Värmland County a method was developed for analysis of the occurrence of artificial land use at lakes and watercourses. With artificial land use is meant land significantly affected by man. Two bases have been used to carry out the analysis. In one of the analysis the vegetation database and in the other GSD¹-Marktäckedata (land cover data) was used (this method has been used by County administrative board in Jönköping County).</p><p>The analysis comprises all watercourses within Alsterälven river basin. The digital water bodies are created by the Swedish Meteorological and Hydrological Institute on the basis of GSD-Översiktskartan (general map). The water layer is derived from GSD-Fastighetskartan (property map) and has been used as water theme in both analyses. In order to make them match each other two models have been used, one manual and one automatic.</p><p>Vegetation data and GSD-Marktäckedata have been complemented with information about cut forest from the Swedish Forest Agency and roads from the Swedish Road Administration. Vegetation data has also been completed with power line area from the forest phase layer and GSD-Marktäckedata with buildings from GSD-Fastighetskartan. The definition artificial land uses has been classified in the vegetation data according to environmental quality criteria; cut forest, field and building sites. In the GSD-Marktäckedata has artificial land use has been classified to environmental quality criteria; cut forest, field, buildings and building sites. The artificial land use types have been summarized individually, totally and indicated as percentage of the total area. The results of the assessment are expressed in a scale of 1-5 for each water body.</p><p>The resolution of the vegetation database is lower than in the GSD-Marktäckedata. The comparison between the vegetation database and GSD-Marktäckedata shows that artificial land use differ in area. In the vegetation database buildings are included in the data base, in GSD-Marktäckedata buildings with a buffer at 20 meters were added to the base map. The buildings in GSD-Marktäckedata cover “more space” and the percentage artificial land became larger.</p>
5

Soil biological indices and nitrogen availability during a simulated transition from inorganic to organic sources of nitrogen

Fauci, Mary F. 21 May 1992 (has links)
Graduation date: 1993
6

Analys av artificiella marktyper vid vatten med hjälp av GIS, Värmlands län 2007

Hansson, Pernilla, Sanfridsson, Christina January 2007 (has links)
On commission of the County administrative board in Värmland County a method was developed for analysis of the occurrence of artificial land use at lakes and watercourses. With artificial land use is meant land significantly affected by man. Two bases have been used to carry out the analysis. In one of the analysis the vegetation database and in the other GSD¹-Marktäckedata (land cover data) was used (this method has been used by County administrative board in Jönköping County). The analysis comprises all watercourses within Alsterälven river basin. The digital water bodies are created by the Swedish Meteorological and Hydrological Institute on the basis of GSD-Översiktskartan (general map). The water layer is derived from GSD-Fastighetskartan (property map) and has been used as water theme in both analyses. In order to make them match each other two models have been used, one manual and one automatic. Vegetation data and GSD-Marktäckedata have been complemented with information about cut forest from the Swedish Forest Agency and roads from the Swedish Road Administration. Vegetation data has also been completed with power line area from the forest phase layer and GSD-Marktäckedata with buildings from GSD-Fastighetskartan. The definition artificial land uses has been classified in the vegetation data according to environmental quality criteria; cut forest, field and building sites. In the GSD-Marktäckedata has artificial land use has been classified to environmental quality criteria; cut forest, field, buildings and building sites. The artificial land use types have been summarized individually, totally and indicated as percentage of the total area. The results of the assessment are expressed in a scale of 1-5 for each water body. The resolution of the vegetation database is lower than in the GSD-Marktäckedata. The comparison between the vegetation database and GSD-Marktäckedata shows that artificial land use differ in area. In the vegetation database buildings are included in the data base, in GSD-Marktäckedata buildings with a buffer at 20 meters were added to the base map. The buildings in GSD-Marktäckedata cover “more space” and the percentage artificial land became larger.
7

Inorganic nitrogen and soil biological dynamics in cover crop systems

Kauffman, Susan Muna 04 March 1994 (has links)
Graduation date: 1994
8

Earthworm populations found near Adelaide, and their influence on the fertility of the soil : thesis submitted for the Degree of Doctor of Philosophy /

Barley, K. P. January 1958 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Faculty of Agricultural Science, 1958. / Includes bibliographical references.
9

Physical processes affecting soil biotic and abiotic responses to disturbance in forest ecosystems of southwestern Oregon /

Borchers, Jeffrey G. January 1990 (has links)
Thesis (Ph. D.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliography (leaves 142-152). Also available on the World Wide Web.
10

Soil quality, microbial community structure, and organic nitrogen uptake in organic and conventional farming systems

Reeve, Jennifer Rose, January 2007 (has links) (PDF)
Thesis (Ph. D.)--Washington State University, August 2007. / Includes bibliographical references.

Page generated in 0.0596 seconds