• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 207
  • 160
  • 35
  • 31
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 518
  • 192
  • 84
  • 73
  • 72
  • 65
  • 58
  • 50
  • 47
  • 47
  • 41
  • 40
  • 38
  • 36
  • 35
  • 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

A study of certain phenological factors as they influence growth in the apple, malus pumila, (mill.)

Beingessner, Henry Francis January 1954 (has links)
The investigation is a study of the science of phenology in relation to the maturation of the fruit of the apple, Malus pumila. (Mill.) through the medium of the Heat Unit Theory, which is an expression of the climatological factor of temperature and more particularly average temperature. The study may be divided into three parts, the first of which introduces the problem of variability in total degree days (the basic unit employed in the Heat Unit Theory) between varieties of apple and between years. A maturity classification is established based on total degree days for several varieties grown at the Central Experimental Farm, Ottawa, Ontario. The second part examines the three basic difficulties encountered in the establishment of a phonological period, namely, when to begin the period, what base or unit temperature below which the apple is assumed not to grow and when to end the period. It was found that starting the phonological period ten days before full bloom gave better precision than when the period was started at full bloom. No one base temperature or combination of temperatures appeared to be entirely satisfactory although the base temperature of 42°F. occupied a medial position. The adoption of the ordinary date of harvest as obtained from field records proved to be as reliable as the index of maturity established by research. Temperature statistics other than the average, such as minimum and night temperatures, used in the calculation of heat units did not improve the precision of a prediction. An accumulation of temperature range appeared superior to accumulation of temperature statistics based on the Heat Unit Theory. No relationship was found to exist between accumulation of sunshine and solar radiation units and the length of the phonological period. In the third part of the investigation the value of total degree days as well as that of various base temperatures is determined for a relatively long period of time at two Experimental Stations, one at Summerland, British Columbia, and the other at Ottawa, Ontario. Actual measurements of the rate of enlargement of an apple are correlated with average temperature for the same period. No increases in precision were noted with the extension of the time interval under study, nor were the correlations obtained indicative of a good relationship between growth of an apple and average temperature. The number of days in the phonological period proved to be as good for prediction purposes as any of the methods used in the investigation, particularly for the climatological environment experienced at Summerland. / Land and Food Systems, Faculty of / Graduate
2

Bidrag till kännedomen om de svenska Fanerogama örternas skottutveckling och öfvervintring

Brundin, Johan Alfred Zakarias, January 3798 (has links)
Thesis--Upsala. / Includes bibliographical references.
3

Changes in phenological time series in Estonia and central and eastern Europe 1951-1998 : relationships with air temperature and atmospheric circulation /

Aasa, Anto, January 2005 (has links) (PDF)
Thesis (doctoral)--University of Tartu, 2005. / Vita. Includes bibliographical references.
4

Temporal Synchrony between Ground-Nesting Bees and Spring Ephemerals in an Eastern Hardwood Forest Ecosystem

Sevenello Montagner, Jose Manuel 17 October 2018 (has links)
Changes in phenology due to climate warming could disrupt temporal overlap between interacting organisms when previously synchronized species respond to climate change at different rates. Phenologies of plants and insects are known to be sensitive to temperature and/or timing of snowmelt, with warmer temperatures and earlier snowmelt generally advancing spring flowering and emergence; however, some groups of pollinators, such as solitary bees, have been little explored in this context. One striking aspect of eastern hardwood forests is the emergence of understory wildflowers each spring, most of which rely, at least to some extent, on wild native pollinators for seed set. Without an understanding of the environmental drivers of phenology of these species, we have little ability to predict whether pollinators will continue to be well synchronized with flowering as the climate changes. In this study, I determined how spring temperatures and timing of snowmelt influence the phenology of spring wildflowers, activity of bees, and their temporal overlap in Gatineau Park, Québec. From 2013 to 2018, I characterized bee activity phenology and flowering phenology of understory plants in multiple study plots, focusing on early-flowering Anemone spp. and later-flowering Trillium grandiflorum. The sampled bee community was dominated by Andrena, Lasioglossum, and Nomada, all of which have similar activity periods. Degree-day accumulation was a better predictor of Anemone and Nomada phenology than were day of year or snowmelt date, whereas T. grandiflorum appeared to be more sensitive to photoperiodic cues; since day of year was the variable that best described its phenology. Activity periods of Andrena and Lasioglossum were equally well described by degree-day accumulation and by day of year. No taxon’s phenology was best predicted by snowmelt date. Despite these differences among taxa in the identities of the best predictors of phenology, bee activity and plant flowering phenologies responded at similar rates to interannual and among-site variation in snowmelt date and early spring temperature. Temporal overlap between flowering and bee activity was similar over the years of this study and was affected neither by snowmelt date nor by temperature. These results suggest that interacting plant and bee taxa may respond to different environmental variables but still maintain their synchrony under the conditions recorded so far.
5

The impact of projected greenhouse gas-induced climate change on the Australian wine industry

Webb, Leanne Beryl Unknown Date (has links) (PDF)
The IPCC Third Assessment report (IPCC 2001a) concludes that Australia has significant vulnerability to the changes in temperature and rainfall projected over the next decades to 100 years. Agriculture and natural resources were two of the key sectors identified as likely to be strongly affected. Climate change will add to the existing, substantial pressures on Australia’s grape and wine industry sector. Vineyards have a life of thirty plus years so right now, when selecting vineyard sites, or when managing existing vineyards, consideration of the changing climate is prudent. (For complete abstract open document)
6

Xanthohumol, a flavonoid from hops (Humulus lupulus) : in vitro and in vivo metabolism, antioxidant properties of metabolites, and risk assessment in humans

Yilmazer, Meltem 05 January 2001 (has links)
Reported here is an investigation to determine the in vitro and in vivo metabolism of xanthohumol (XN). XN is the major prenylated flavonoid of the female inflorescences (cones) of the hop plant (Humulus lupulus). It is also a constituent of beer, the major dietary source of prenylated flavonoids. Recent studies have suggested that XN may have potential cancer chemopreventive activity but little is known about its metabolism. We investigated the in vitro metabolism of XN by rat and human liver microsomes, and cDNA-expressed cytochrome P450s, and the in vivo metabolism of XN by rats. The metabolites and conjugates were identified by using high-pressure liquid chromatography, liquid chromatography-mass spectrometry, and nuclear magnetic resonance. The antioxidant properties of two metabolites and two glucuronides were examined. The possible risk of XN consumption from beer or dietary supplements is discussed. The involvement of metabolites of XN in cancer chemoprevention remains to be established. / Graduation date: 2001
7

Application of phenology to assist in hyperspectral species classification of a northern hardwood forest /

Sprehe, Gretchen M. January 2005 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 93-96).
8

Climate and phenology in the Baraboo Hills Natural Area

Kopitzke, David Arnold, January 1967 (has links)
Thesis (M.A.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
9

Crop Growth and Development for Irrigated Chile (Capiscum annuum)

Silvertooth, J.C., Brown, Paul, Walker, Stephanie 09 1900 (has links)
2 pp.
10

Establishing the Role of Digital Repeat Photography in Understanding Phenology and Carbon Cycling in a Subarctic Peatland

Garnello, Anthony John, Garnello, Anthony John January 2017 (has links)
In this thesis, I establish and explore the role of phenology in understanding the rapidly changing environment of a subarctic peatland. First, I demonstrate how digital repeat photography can be used to characterize and differentiate distinct plant communities using two years of images. Each habitat is composed of different plant functional groups, promoting the individualistic approach to characterization that near-earth remote sensing tools can provide. The camera-product Relative Greenness successfully characterized interannual variability in seasonal growth for each habitat type. Across habitats, there was a direct relationship between advancement of spring onset and active season growth though this overall pattern showed habitat-specific variance. The camera images were also useful in characterizing the flowering phenology of an ​eriophorum​-rich fen habitat, for which a metric named Intensity was created. These results suggest that employment of phenology cameras in highly heterogeneous subarctic environments is a robust method to characterize phenology on a habitat to species scale. Next, I explored the role that this phenology product has in modeling Net Ecosystem Exchange (NEE) also measured at the field site. I hypothesized that the explanatory power of the phenology index, which is conceptually tied to a measure of photosynthetic capacity, would be tightly linked to the timescale it was used for: At sub-daily timescales, environmental forces would dominate, though when averaged over days to weekly scales, the biology represented through the camera index would be more influential. I show that at multiple time scales the environmental factors outperform the camera index when modeling NEE. Together, these studies begin to explore the applicability of phenology camera systems in subarctic environments.

Page generated in 0.0439 seconds