scholarly journals Influence of Gap Size and Position within Gaps on Light Levels

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Benoit Gendreau-Berthiaume ◽  
Daniel Kneeshaw
Keyword(s):  
Temperate Forest ◽  
Light Level ◽  
Light Distribution ◽  
Gap Size ◽  
Maximum Light ◽  
The North ◽  
Light Levels ◽  
Hemispherical Photographs ◽  
Northern Edge ◽  
South Axis

The previous studies have reported maximum light levels at different positions within gaps but many of these studies are based on gaps of different size. The objective of this study is to evaluate the influence of gap size and position within gap on light distribution in gaps and under the canopy north of gaps in a mixedwood temperate forest. For three gap sizes, with gap widths ranging between 0.5 and 1.5 times the height of the surrounding stand, light was measured at different positions along the north-south axis in each gap using two different techniques (hemispherical photographs and instantaneous measurements). In small gaps, the position with the most light was close to the northern edge although not under the canopy north of the gap. For both methods, the position with the highest light level shifted from the north towards the center of gaps as gap size increased which clarifies some of the variability in light measurements previously observed in gap studies. Higher light levels in the northern part of small and medium gaps compared to the southern portion could allow management of a mixture of species with intolerant species in the northern portions of gaps and tolerant species to the south.

Improving gap light index (GLI) to quickly calculate gap coordinates

2008 ◽  
Vol 38 (9) ◽  
pp. 2337-2347 ◽  
Author(s):  
Lile Hu ◽  
Jiaojun Zhu
Keyword(s):  
Canopy Gap ◽  
Canopy Height ◽  
Gap Size ◽  
Light Regimes ◽  
Light Levels ◽  
Understory Plants ◽  
Sampling Points ◽  
Hemispherical Photographs ◽  
Geometric Calculation

Understory light is essential to the establishment and growth of understory plants and varies temporally and spatially within gaps. The previously defined gap light index (GLI) is a good model for assessing understory light levels, but it is time-consuming to determine gap coordinates, which are crucial to GLI, for numerous points within a gap. This paper introduces the geometric calculation (GeoCalc) of gap coordinates. GeoCalc quickly obtains gap coordinates for any specified point within a canopy gap and takes into account the tridimensional profile of the gap and the slope and aspect of the ground. The GeoCalc-based GLI was validated by the GLI derived from hemispherical photographs taken at 93 sampling points within seven natural gaps. Our results demonstrate that GeoCalc-based GLI was strongly positively correlated and not significantly differed from the GLI derived from hemispherical photographs. Next, to analyze gap light regimes and the effects of gap size, canopy height, and topography, three natural gaps of various size were selected and simulated as nine gaps with 1 and 1.5 times canopy height or on the opposite slope. Finally, we have summarized characteristics of GeoCalc-based GLI and its application.

Change of color appearance due to extremely high light level: corresponding colors under 100 and 3000 cd/m2

2019 ◽  
Vol 2019 (1) ◽  
pp. 320-325 ◽  
Author(s):  
Wenyu Bao ◽  
Minchen Wei
Keyword(s):  
Light Level ◽  
Limited Range ◽  
High Light ◽  
Color Preference ◽  
Color Appearance ◽  
Appearance Model ◽  
Color Matching ◽  
Light Levels ◽  
Appearance Models ◽  
Psychophysical Study

Great efforts have been made to develop color appearance models to predict color appearance of stimuli under various viewing conditions. CIECAM02, the most widely used color appearance model, and many other color appearance models were all developed based on corresponding color datasets, including LUTCHI data. Though the effect of adapting light level on color appearance, which is known as "Hunt Effect", is well known, most of the corresponding color datasets were collected within a limited range of light levels (i.e., below 700 cd/m2), which was much lower than that under daylight. A recent study investigating color preference of an artwork under various light levels from 20 to 15000 lx suggested that the existing color appearance models may not accurately characterize the color appearance of stimuli under extremely high light levels, based on the assumption that the same preference judgements were due to the same color appearance. This article reports a psychophysical study, which was designed to directly collect corresponding colors under two light levels— 100 and 3000 cd/m2 (i.e., ≈ 314 and 9420 lx). Human observers completed haploscopic color matching for four color stimuli (i.e., red, green, blue, and yellow) under the two light levels at 2700 or 6500 K. Though the Hunt Effect was supported by the results, CIECAM02 was found to have large errors under the extremely high light levels, especially when the CCT was low.

scholarly journals A high-resolution solar spectrum 2000 Å–2200 Å

1970 ◽  
Vol 36 ◽  
pp. 271-273
Author(s):  
B. B. Jones ◽  
B. C. Boland ◽  
R. Wilson ◽  
S. T. F. Engstrom
Keyword(s):  
High Resolution ◽  
Solar Spectrum ◽  
Solar Image ◽  
Roll Control ◽  
North East ◽  
The North ◽  
Alignment System ◽  
Optical Alignment ◽  
South Axis ◽  
System Operating

A high-resolution solar spectrum in the range 2000–2200 Å was obtained in a recent flight of a sunpointing Skylark rocket. This was launched at 04.21 hr UT on April 22, 1969 from Woomera and reached an apogee of 178 km. An optical alignment system operating on the main vehicle pointing system gave a net stabilisation of ±3 arc sec in the position of the solar image relative to the spectrograph slit. The slit, of length 1.0 mm, was set in the north-east quadrant parallel to and 5 arc min from the north/south axis, its lower edge being 1 arc min from the equator. The roll control of ±2.5° was provided entirely by the standard Elliott Bros. type of vehicle stabilisation.

Light or presence of host trees: which is more important for the strangler fig?

1999 ◽  
Vol 15 (5) ◽  
pp. 589-602 ◽  
Author(s):  
Vidya R. Athreya
Keyword(s):  
Host Species ◽  
National Park ◽  
Canopy Cover ◽  
Light Level ◽  
Southern India ◽  
Evergreen Forest ◽  
Primary Forest ◽  
Light Levels ◽  
Host Trees ◽  
Main Host

Strangler fig density varied considerably in the evergreen forest of Karian Shola National Park, southern India, with 11 individuals ha−1 in an open trail area and 5.6 individuals ha−1 within the primary forest area. The index of light level was assessed by estimating the percentage of upper canopy cover along the longitudinal centre of ten, 500-m × 20-m plots in each of the two areas of the evergreen forest. However, the increase in strangler fig density was not correlated to light levels but was significantly correlated to the numbers of their main host species in the two areas. In Karian Shola National Park, strangler figs occurred predominantly on a few host species with 20 and 50% of strangler figs growing on Vitex altissima, Diospyros bourdilloni and Eugenia/Syzygium spp. in the primary forest and trail areas respectively. Both young and established strangler figs were recorded mainly on larger individuals of their host trees indicating that older host trees are likely to be more suitable for the germination and establishment of strangler figs. The reason for the above could be the higher incidence of humus-filled and decaying regions in the older host trees which would provide an assured supply of nutrients for the establishing strangler fig.

scholarly journals DIVERSIFICATION OF GAS SUPPLIES AS A CORNERSTONE OF GAS SECURITY IN THE FRAMEWORK OF THE THREE SEAS INITIATIVE

2021 ◽  
Vol 2 (2) ◽  
pp. 1-8
Author(s):  
Danylo Stonis
Keyword(s):  
Natural Gas ◽  
Eastern Europe ◽  
Central Europe ◽  
Security Policy ◽  
Energy Transport ◽  
Transportation Infrastructure ◽  
The European Union ◽  
The North ◽  
Gas Market ◽  
South Axis

The article overviews approaches to the diversification of gas supplies in the framework of the Three Seas Initiative. The modern geopolitical situation in Eastern and Central Europe is characterized by transformation processes in the energy sector. Due to the implementation of decarbonization policy in the European Union and subsequent shift from coal as a main energy source, a need in alternative fuel sources, such as natural gas, emerges. Therefore, a significant increase in natural gas consumption is expected, which raises a number of issues, such as dependence on a single gas supplier and orientation of the EU’s gas transmission system in East-West direction only. This issue is crucial for Eastern and Central European states, due to the underdeveloped gas infrastructure in the region and heavy dependence on a single gas supplier, such as Russia or Turkey. Hence, the Three Seas Initiative is considered as a powerful tool, designed to develop energy, transport and digital infrastructure of the region in the North-South direction, where one of the most potentially promising projects within the framework of the Three Seas Initiative is represented by the development of gas infrastructure, aimed at solving the diversification of supplies in the gas market in Eastern and Central Europe. The implementation of developed gas infrastructure and diversification of gas supplies consists of several regional projects that are relevant for those countries in the region in which they are implemented in particular and for all member states of the Three Seas Initiative in general. The main purpose of the implementation of these projects is the creation of a unified natural gas transportation infrastructure in Eastern Europe along the North-South axis. The result of such a grand reorganization in the field of gas supplies to Europe will be an increase in the number of independent suppliers in the European gas market and a decrease in the dependence of the EU countries on gas supplies from Russia. In the article, the author traced in detail the tendency of the formation of energy infrastructure along the North-South axis with focus on the projects that are being implemented by each of the participating countries within the framework of the Three Seas Initiative. This approach allows to assess the scale and integrity of the gas transportation infrastructure, that is being created in the Eastern Europe region and its contribution to the common European energy security policy.

scholarly journals Interactive effects of temperature and light on reattachment success in the brown alga Fucus radicans

2019 ◽  
Vol 62 (1) ◽  
pp. 43-50
Author(s):  
Ellen Schagerström ◽  
Tiina Salo
Keyword(s):  
High Temperature ◽  
Water Temperature ◽  
Asexual Reproduction ◽  
Net Primary Production ◽  
Light Level ◽  
Interactive Effects ◽  
Low Light ◽  
Dispersal Capacity ◽  
Light Levels ◽  
The Baltic

Abstract Fucus radicans is an endemic habitat-forming brown macroalga in the Baltic Sea that commonly complements its sexual reproduction with asexual reproduction. Asexual reproduction in F. radicans takes place through formation of adventitious branches (hereafter fragments), but the exact mechanisms behind it remain unknown. We assessed experimentally the importance of two environmental factors determining the re-attachment success of F. radicans fragments. By combining different light conditions (daylength and irradiance; high or low light) and water temperature (+14°C and +4°C), we mimicked ambient light and temperature conditions of winter, spring/autumn and summer for F. radicans. Fragments were able to re-attach in all tested conditions. Temperature and light had an interactive impact on re-attachment: the combination of high temperature and high light level resulted in the highest re-attachment success, while light level had no effects on re-attachment success in cooler water temperature and the re-attachment success in high temperature under low light levels was very low. The results suggest that rhizoid formation, and thus re-attachment success, may depend on the net primary production (metabolic balance) of the fragment. However, whether the re-attachment and asexual reproduction success simply depends on photosynthetic capacity warrants further mechanistic studies. Understanding the mechanisms of asexual reproduction in F. radicans is important in order to assess the dispersal capacity of this foundation species.

The onset of the early Toarcian flooding of the Pliensbachian carbonate platform of Central Tunisia (North-South Axis) as inferred from trace fossils and geochemistry

2021 ◽  
pp. SP514-2021-10
Author(s):  
Matías Reolid ◽  
Mohamed Soussi ◽  
Jesús Reolid ◽  
Wolfgang Ruebsam ◽  
Ilef Belhaj Taher ◽  
...  
Keyword(s):  
Carbonate Platform ◽  
High Energy ◽  
Trace Fossils ◽  
Energy Conditions ◽  
Local Conditions ◽  
Content Type ◽  
The North ◽  
Sea Bottom ◽  
Supplementary Material ◽  
South Axis

AbstractThe flooding of the Lower Jurassic shelf in the North Gondwana Palaeomargin during the early Toarcian occurred on a fragmented and irregular topography affected by differential subsidence—due to the activity of listric faults along the North-South Axis of Tunisia—that favoured lateral changes in facies and thickness at a kilometric scale. The onset of Toarcian sedimentation (Polymorphum ammonite Zone, NJT5c nannofossil Subzone) in two adjacent sections was characterised by the deposition of limestones under high-energy conditions. The Châabet El Attaris section was located in a depressed sub-basin, and recorded restricted environmental conditions owing to water stagnation and an oxygen-depleted sea-bottom. Therefore, dark mudstones developed, with increased TOC contents and enhanced accumulation of redox-sensitive elements. The sedimentation of limestones bearing gutter cast structures is related to gravity flows probably linked to storm activities. These processes favoured the remobilization of sediments at the sea floor, as well as oxygen input to bottom waters, as shown by the record of trace fossils including Zoophycos, Ophiomorpha, and secondarily, Chondrites and Diplocraterion. The thinly interbedded dark mudstones are locally rich in thin-shelled bivalves that re-colonised the sea bottom after the sedimentation of these high-energy deposits, and subsequently underwent mass mortality related to the return of oxygen-depleted conditions. The Kef El Hassine section is located in the upper part of a tilted, less subsident block, as indicated by its reduced thickness compared with the Châabet El Attaris section; the absence of dark mudstones implies oxic conditions. The Polymorphum Zone consists of limestones showing evidence of sedimentation under high-energy conditions, along with hardgrounds. The occurrence of Zoophycos (deep-tiers) in the upper part of some limestone beds of the Polymorphum Zone is linked to minor erosive processes. The top of the high-energy sequence—below the deposits of a marly interval corresponding to the Levisoni Zone—is interpreted as a hardground given the high content of belemnites and Arenicolites, some of them boring on the eroded Zoophycos and Thalassinoides. This study shows that the sedimentary expression of the Jenkyns Event is not uniform across Tunisia, supporting the importance of local conditions in determining the development of anoxic conditions.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5510162

Sign in / Sign up

Export Citation Format

Share Document