Growth of understory Piceaglauca, Calamagrostiscanadensis, and Epilobiumangustifolium in relation to overstory light transmission

1994 ◽  
Vol 24 (6) ◽  
pp. 1193-1198 ◽  
Author(s):  
V.J. Lieffers ◽  
K.J. Stadt
Keyword(s):  
Light Transmission ◽  
Basal Area ◽  
Diameter Ratio ◽  
Light Transmittance ◽  
Height Increment ◽  
Light Conditions ◽  
Incoming Light

The potential for use of a partial canopy for controlling growth of Calamagrostiscanadensis (Michx.)•Beauv., and Epilobiumangustifolium L. among regenerating Piceaglauca (Moench) Voss saplings was assessed in the understory of 24 established stands in the P. glauca–Viburnum–Rubuspubescens association of the lower boreal cordilleran ecoregion of Alberta. Stand overstories were dominated by Populustremuloides Michx., P. glauca, or were a mixture of these two species The composition, basal area, and light transmission of the overstory of each stand were measured. Hardwood-dominated overstories transmitted between 14 and 40% of incoming light while P. glauca canopies transmitted between 5 and 11 % of light. Cover and height of C. canadensis and E. angustifolium decreased with decreasing light transmission; at 40% light, both species were greatly reduced compared with open-grown conditions and both were virtually eliminated from stands with less than 10% light. The annual height increment of P. glauca saplings increased from 5 cm at 10% light to 25 cm at 40 % light; the latter increment was approximately equal to growth in 100% light conditions. The number of buds, the diameter of the current leader, and the height to diameter ratio of the tree also increased with light transmittance.

Influences of paper birch competition on growth of understory white spruce and subalpine fir following spacing

2003 ◽  
Vol 33 (10) ◽  
pp. 1962-1973 ◽  
Author(s):  
Philip G Comeau ◽  
Jian R Wang ◽  
Tony Letchford
Keyword(s):  
Picea Glauca ◽  
Volume Growth ◽  
Basal Area ◽  
White Spruce ◽  
Light Transmittance ◽  
Height Increment ◽  
Growth Responses ◽  
Subalpine Fir ◽  
Volume Increment ◽  
Paper Birch

Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we examine relationships between growth of understory white spruce (Picea glauca (Moench) Voss), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and level of birch retention. Our objectives were to evaluate the effectiveness of selected measures of competition for estimating the effects of the residual birch and to evaluate the influence of residual birch densities on growth responses of naturally regenerated subalpine fir and white spruce. Basal area of Scouler willow (Salix scouler iana Barratt) and birch were found to effectively predict light transmittance (diffuse noninterceptance). The best models for predicting 4-year volume growth of subalpine fir and white spruce incorporate initial crown volume of the subject trees and transmittance as independent variables. Lorimer's index and Hegyi's index gave similar results to those obtained using basal area and transmittance, suggesting that there is little benefit in including measurements of proximity in a competition index. For both species, the correlation between basal area increment and light was substantially stronger than observed for volume increment. However, height increment of both subalpine fir and spruce was only weakly correlated with measured light levels. The ratio of height increment to volume increment decreased with both increasing initial height and transmittance for subalpine fir and white spruce.

scholarly journals Dynamics of Melting Process in Phase Change Material Windows Determined Based on Direct Light Transmission

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 721
Author(s):  
Dariusz Heim ◽  
Michał Krempski-Smejda ◽  
Pablo Roberto Dellicompagni ◽  
Dominika Knera ◽  
Anna Wieprzkowicz ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Light Transmission ◽  
Melting Process ◽  
Refraction Index ◽  
Light Transmittance ◽  
Reference Case ◽  
Solar Radiation Intensity ◽  
Direct Light ◽  
Change Material

Detailed analyses of melting processes in phase change material (PCM) glazing units, changes of direct transmittance as well as investigation of refraction index were provided based on laboratory measurements. The main goal of the study was to determine the direct light transmittance versus time under constant solar radiation intensity and stable temperature of the surrounding air. The experiment was conducted on a triple glazed unit with one cavity filled with a paraffin RT21HC as a PCM. The unit was installed in a special holder and exposed to the radiation from an artificial sun. The vertical illuminance was measured by luxmeters and compared with a reference case to determine the direct light transmittance. The transmittance was determined for the whole period of measurements when some specific artefacts were identified and theoretically explained based on values of refractive indexes for paraffins in the solid and liquid state, and for a glass. The melting process of a PCM in a glass unit was identified as a complex one, with interreflections and refraction of light on semi layers characterized by a different physical states (solid, liquid or mushy). These optical phenomena caused nonuniformity in light transmittance, especially when the PCM is in a mushy state. It was revealed that light transmittance versus temperature cannot be treated as a linear function.

scholarly journals The influence of stand canopy openness on the growth of common yew (Taxus baccata L.)

2015 ◽  
Vol 76 (1) ◽  
pp. 42-48 ◽  
Author(s):  
Marzena Niemczyk ◽  
Anna Żółciak ◽  
Wrzesiński Piotr
Keyword(s):  
Light Transmission ◽  
Abies Alba ◽  
Extended Period ◽  
European Beech ◽  
Ex Situ ◽  
Canopy Openness ◽  
Silver Fir ◽  
Taxus Baccata ◽  
Height Increment ◽  
Transmission Index

Abstract The aim of this study was to evaluate the development of common yew, Taxus baccata L., with respect to canopy openness. The plants were growing in ex-situ conservation plantations (established in 2008) in the understory of different tree species. Eleven forest plantations belonging to the following five forest districts were inventoried: Rokita, Baligród, Kołaczyce, Międzylesie and Henryków. In each plantation, the height and height increment of 200 yews were measured and gap light transmission indices were determined. The canopy species affecting yew growth most significantly were oak (Quercus sp.) and Scots pine (Pinus sylvestris L.), followed by Norway spruce (Picea abies Karst.), silver fir (Abies alba L.) and European beech (Fagus sylvatica L.). The most favorable development of yew occurred at 30% canopy openness. An increasing light transmission index correlated with a decrease in the proportion of treelike yews. An insufficient amount of light resulted in a low height increment of yews growing under the canopy and an extended period of direct competition of yews with herbaceous species.

The effect of fluctuating light on canopy photosynthesis: a focus on a chlorophyll-deficient Soybean mutant

2021 ◽  
Author(s):  
Nicole Salvatori
Keyword(s):  
Steady State ◽  
Dynamic Environment ◽  
Regulatory System ◽  
Total Carbon ◽  
Light Transmittance ◽  
Photochemical Quenching ◽  
Natural Environments ◽  
Deficient Mutant ◽  
Light Conditions ◽  
Variable Light

<p>In natural environments plants are subjected to variable light conditions and therefore need an efficient regulatory system to regulate photosynthesis and the downstream metabolism. Most of the measurements available are taken at steady state and at leaf level but those may overestimate total carbon uptake in a more dynamic environment. Furthermore, some plants may be more adapted than others to deal with light fluctuations and therefore is difficult to draw general conclusions. We then grew a commercial soybean variety and a chlorophyll deficient mutant in a recently developed growth chamber system (DYNAMISM) which allowed to obtain instantaneous gas exchange data at canopy level for several weeks. By doing so we could investigate both short term responses and long term adaptations to light dynamic conditions of the two varieties. At steady state, chlorophyll deficient crops are thought to have a similar or even a higher photosynthetic rate compared to the green wildtypes, enhanced by a higher light transmittance throughout the canopy. But little is known about how they respond to fluctuations in light. The two varieties were grown either in fluctuating (F) or non-fluctuating (NF) light conditions to evaluate how variable light would affect biomass accumulation. Two different light treatments were applied, low light (LL) and high light (HL) with different light intensities and amplitude of fluctuations. The LL treatment did not entail any difference among F and NF in both varieties. The chlorophyll-deficient mutant was instead found to be susceptible to the fluctuations of light in the HL treatment, by accumulating less biomass. It is hypothesised that this might be due to its longer non‐photochemical quenching relaxation time  in light transitions, but other acclimatation mechanisms need to be investigated.</p>

scholarly journals Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Jae-Hyung Park ◽  
Ji-Won Jang ◽  
Jae-Hak Sim ◽  
Il-Jin Kim ◽  
Dong-Jin Lee ◽  
...  
Keyword(s):  
Light Transmission ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Light Transmittance ◽  
Solar Light ◽  
Solution Temperature ◽  
Smart Window ◽  
Thermoresponsive Polymers ◽  
Smart Windows ◽  
Hydrogel Films

Thermoresponsive polymers that exhibit phase transition in response to temperature change can be used as material for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermoresponsive polymers for a smart window that can be used over a wide temperature range is required. Therefore, to obtain smart window materials that can be used at various temperatures, three-dimensional thermoresponsive P(NIPAm-co-BA) hydrogels were prepared by free radical polymerization from main monomer N-isopropylacrylamide, comonomer butyl acrylate, and crosslinking agent N,N′-methylenebisacrylamide (MBAm) in this study. This study examined the effect of BA content on the lower critical solution temperature (LCST) and the solar light transmittance of crosslinked P(NIPAm-co-BA) hydrogel films. The LCST of hydrogel films was found to be significantly decreased from 34.3 to 29.5°C with increasing BA content from 0 to 20 mol%. It was found that the transparent films at T=25°C (T<LCST) were converted to translucent films at a higher temperature (T=45°C) (T>LCST). These results suggested that the crosslinked P(NIPAm-co-BA) hydrogel materials prepared in this study could have high potential for application in smart window materials.

scholarly journals Variability of light transmission through Arctic land-fast sea ice during spring

2013 ◽  
Vol 7 (3) ◽  
pp. 977-986 ◽  
Author(s):  
M. Nicolaus ◽  
C. Petrich ◽  
S. R. Hudson ◽  
M. A. Granskog
Keyword(s):  
Sea Ice ◽  
Spatial Variability ◽  
Physical Properties ◽  
Snow Cover ◽  
Light Transmission ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Optical Measurements ◽  
Light Transmittance ◽  
Seasonal Evolution

Abstract. The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.

Preparation of MgAl2O4 Transparent Nano-Ceramics and their Light Transmission Properties

2007 ◽  
Vol 336-338 ◽  
pp. 2296-2299 ◽  
Author(s):  
Jian Qi Qi ◽  
Tie Cheng Lu ◽  
Xiang Hui Chang ◽  
Mu Yun Lei ◽  
Cun Xin Huang
Keyword(s):  
Light Transmission ◽  
Ultrahigh Pressure ◽  
Light Transmittance ◽  
Affecting Factors ◽  
Pressure Source ◽  
Transmission Properties ◽  
Grain Sizes ◽  
Nano Powder ◽  
Ceramic Samples ◽  
Sintering Method

MgAl2O4 transparent nano-ceramic samples have been successfully prepared by ultrahighpressure- sintering method. The ultrafine MgAl2O4 nano-powder was obtained by high-temperaturecalcination method. The samples were sintered at relatively low temperatures (540, 620 and 700°C) under ultrahigh pressures (3, 3.7 and 5GPa) with a six-pressure-source and hexahedral anvil machine that is customarily used for diamond synthesis. The average grain sizes of the prepared samples range from 50 to 75nm. All of the samples sintered under different conditions are transparent. The sample sintered at 620°C under 3.7GPa has the highest density as well as the highest light transmittance (about 50%) at 1300 ~ 1700 nm. The results showed that the ultrahigh-pressure-sintered samples exhibit unique light transmission properties though their densities are not much higher (<97%), compared to the samples, of which densities are higher (>99.5%), obtained by conventional hot-pressing or hot isotopic pressing sintering methods. The light transmittance, its affecting factors and transparent mechanism of the MgAl2O4 samples have been discussed.

Flixweed (Descurainia sophia) Shade Tolerance and Possibilities for Flixweed Management Using Rapeseed Seeding Rate

2017 ◽  
Vol 31 (3) ◽  
pp. 477-486
Author(s):  
Christopher A. Landau ◽  
Brian J. Schutte ◽  
Abdel O. Mesbah ◽  
Sangamesh V. Angadi
Keyword(s):  
Field Study ◽  
Light Transmission ◽  
Light Transmittance ◽  
Seeding Rate ◽  
Seed Oil Content ◽  
Greenhouse Study ◽  
Study Results ◽  
Rate Effects ◽  
Shade Tolerant Species ◽  
Photosynthetic Responses

Brassicaceae weeds can be problematic in canola varieties that have not been modified to resist specific broad-spectrum herbicides. The overall objective of this study was to evaluate the potential for increased rapeseed seeding rate as a management strategy for flixweed. To accomplish this objective, a field study was conducted to determine crop seeding rate effects on canopy light transmission and rapeseed yield characteristics, as well as a greenhouse study to determine morphological and photosynthetic responses of flixweed to decreasing irradiance levels. Results from the field study indicated that light transmittance through the canopy decreased linearly as crop seeding rate increased from 1.8 to 9.0 kg ha-1. Increasing crop seeding rate did not influence rapeseed aboveground biomass, seed yield, and harvest index, but negatively affected rapeseed seed oil content in one of two site-years. Greenhouse study results indicated that declining irradiance levels caused reductions in flixweed biomass, root allocation, and photosynthetic light compensation point. Flixweed leaf allocation, foliage area ratio, and specific foliage area increased in response to decreasing irradiance levels. Combined results of field and greenhouse studies suggest that increasing rapeseed seeding rate can suppress flixweed growth while not causing yield penalties from increased intraspecific competition. However, increased rapeseed seeding rate might not be an adequate control strategy on its own because flixweed displays characteristics of a shade-tolerant species.

scholarly journals Variability of light transmission through Arctic land-fast sea ice during spring

2012 ◽  
Vol 6 (5) ◽  
pp. 4363-4385 ◽  
Author(s):  
M. Nicolaus ◽  
C. Petrich ◽  
S. R. Hudson ◽  
M. A. Granskog
Keyword(s):  
Sea Ice ◽  
Spatial Variability ◽  
Physical Properties ◽  
Large Scale ◽  
Light Transmission ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Optical Measurements ◽  
Light Transmittance ◽  
Seasonal Evolution

Abstract. The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along repeated (March, May, June 2010) transects under un-deformed land-fast sea ice at Barrow, Alaska. The objective was to quantify seasonal evolution and spatial variability of light transmittance through snow and sea ice. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for Chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt may cause as much spatial variability of relative light transmittance as the contrast of ponded and white ice during summer. In both instances, a spatial variability of up to three times above and below the mean was measured. In addition, we found a thirtyfold increase of light transmittance as a result of partial snowmelt. Hence, the seasonal evolution of transmittance through sea ice exceeded the spatial variability. Nevertheless, more comprehensive under-ice radiation measurements are needed for a more generalized and large-scale understanding of the under-ice energy budget for physical, biological, and geochemical applications.

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