scholarly journals Switchgrass Leaf Area Index and Light Extinction Coefficients

2011 ◽  
Vol 103 (1) ◽  
pp. 119-122 ◽  
Author(s):  
Jim Kiniry ◽  
Mari-Vaughn Johnson ◽  
Robert Mitchell ◽  
Ken Vogel ◽  
Jerry Kaiser ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Light Extinction ◽  
Area Index ◽  
Extinction Coefficients

Light extinction coefficients specific to the understory vegetation of the southern boreal forest, Quebec

2000 ◽  
Vol 30 (1) ◽  
pp. 168-177 ◽  
Author(s):  
Isabelle Aubin ◽  
Marilou Beaudet ◽  
Christian Messier
Keyword(s):  
Boreal Forest ◽  
Leaf Area Index ◽  
Light Transmission ◽  
Light Availability ◽  
Understory Vegetation ◽  
Light Extinction ◽  
Forest Types ◽  
Area Index ◽  
K Value ◽  
Extinction Coefficients

This study was conducted in six different forest types in Abitibi, Que., (i) to identify the factors that most influence understory light transmission in the southern boreal forest and (ii) to develop light extinction coefficients (k), which could be used to simulate light transmission in the understory. Light availability and understory vegetation (cover, composition, vertical distribution, and leaf area index) were characterized within three strata (0.05-5 m) in a total of 180 quadrats. Calculated k values were based on measured light availability and leaf area index. These values varied among forest types, strata, understory vegetation types, and cover in the upper stratum. The highest k values were generally associated with a dense stratum of Acer spicatum Lam. We developed five sets of k values based on the factors that most affected light transmission. Measured transmission (Tm) was compared with transmission predicted (Tp) from each set of k values. Light transmission predicted using a single k value (mean k = 0.54) underestimated Tm. More accurate predictions were obtained when we used the other four sets of k values. Our results indicate that, in the southern boreal forest, the understory vegetation can be quite heterogeneous and patterns of light transmission cannot be accurately simulated using a unique k value. However, the various sets of k values developed in this study could be used in prediction models of forest dynamics to obtain relatively good predictions of understory light extinction in forest types similar to the ones studied here.

CANOPY CHARACTERISTICS OF CONTRASTING CLONES OF CACAO (THEOBROMA CACAO)

2002 ◽  
Vol 38 (3) ◽  
pp. 359-367 ◽  
Author(s):  
A. J. Daymond ◽  
P. Hadley ◽  
R. C. R. Machado ◽  
E. Ng
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Theobroma Cacao ◽  
Light Interception ◽  
Canopy Architecture ◽  
Mature Trees ◽  
Area Index ◽  
Mean Values ◽  
Extinction Coefficients ◽  
The Relationship

Canopy characteristics (leaf area index, fractional light interception, extinction coefficient) of mature trees of ten clonally propagated cacao cultivars were measured over a period of 14 months at an experiment site in Bahia, Brazil. Differences in leaf area index between clones became more pronounced over time. When an approximately constant leaf area index was reached (after about nine months), the leaf area index varied between clones from 2.8 to 4.5. Clonal differences in the relationship between leaf area index and fractional light interception implied differences in canopy architecture, as reflected by the range of extinction coefficients (mean values ranged from 0.63 for the clone TSH-565 to 0.82 for CC-10). The results demonstrate the potential for breeding more photosynthetically efficient cacao canopies.

Estimating salal leaf area index and leaf biomass from diffuse light attenuation

1990 ◽  
Vol 20 (9) ◽  
pp. 1265-1270 ◽  
Author(s):  
N. J. Smith ◽  
D. R. Clark
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Light Attenuation ◽  
Major Axis ◽  
Weibull Model ◽  
Leaf Biomass ◽  
Diffuse Light ◽  
Area Index ◽  
Extinction Coefficients ◽  
Reduced Major Axis

Salal (Gaultheriashallon Pursh) leaf area index and leaf biomass were estimated from 37 quadrat samples in 13 stands dominated by Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) on eastern Vancouver Island, British Columbia. Leaf area index and biomass were predicted from a Beer's Law light attenuation model using diffuse photosynthetically active radiation (400–700 nm wavelength). The extinction coefficients, determined using reduced major axis maximum likelihood, were 0.8055 m2/m2 for leaf area index and 0.0069 g/m2 for leaf biomass. Salal leaf area index and biomass were then predicted for any convenient height in the understory canopy using a cumulative Weibull model based on dominant salal height per quadrat. The models are of use for objectively assessing the amount of Columbian black-tailed deer (Odocoileushemionuscolumbianus Richardson) winter browse and to quantify competitive leaf area.

Tracking leaf area index and coefficient of light extinction over the harvesting cycle of black wattle

2016 ◽  
Vol 27 (6) ◽  
pp. 1211-1217 ◽  
Author(s):  
Alexandre Behling ◽  
Carlos Roberto Sanquetta ◽  
Ana Paula Dalla Corte ◽  
Sylvio Péllico Netto ◽  
Aurélio Lourenço Rodrigues ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Light Extinction ◽  
Area Index ◽  
Black Wattle

Canopy Development, Light Interception and Seed Production in Sunflower as Influenced by Temperature and Radiation

1984 ◽  
Vol 11 (4) ◽  
pp. 255 ◽  
Author(s):  
HM Rawson ◽  
RL Dunstone ◽  
MJ Long ◽  
JE Begg
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Seed Production ◽  
Harvest Index ◽  
Growth Patterns ◽  
Light Extinction ◽  
Seed Number ◽  
Area Index ◽  
Radiation Interception ◽  
Temperature Regimes

Well watered mini-crops of sunflower were grown either in summer or winter in glasshouses maintained under five temperature regimes and a 16 h photoperiod. A field crop was grown concurrently with the summer glasshouse study. Summer radiation (25.5 MJ day-1) increased the size and/or number of many of the variables measured compared with winter radiation (9.5 MJ day-1). However, there was interaction between light and temperature upon phenological development, plant height, leaf number and harvest index. Seed production declined at temperatures above 18/13°C in summer and above 24/19°C in winter radiation, but fatty acid composition of the seed oil changed progressively with increasing temperature and was unaffected by radiation. Leaf area per plant increased faster under summer than winter radiation and in almost all temperature regimes reached considerably higher final values which resulted in a greater percentage of the incident radiation being intercepted. Temperature, though affecting the growth patterns and final areas of individual leaves in the canopies, did not alter the relationship between leaf area index and radiation interception. The light extinction coefficient changed with leaf area index and differed between summer and winter. Biomass per plant at maturity (B, g) was best related to radiation interception up to anthesis (I, MJ m-2), such that B = -234 + 541ogl, r2 = 0.91, but seed number (S) was correlated similarly with radiation interception and with the number of degree days (D) accumulated between floral initiation and anthesis (S = 1137+ 0.0051-0.762D, R2 = 0.90). Yield (Y, g per plant) was dependent on seed number, mean temperature (T) and radiation intercepted between anthesis and maturity, and the leaf area present at anthesis. However, over 97% of the variation in yield could be accounted for by the temperature and radiation factors in the manner Y = 39.07+0.047I- 1.26T. Harvest index and yield were not correlated for the cultivar examined.

Effects of shading on the growth and nitrogen content of green panic and Siratro in pure and mixed swards defoliated at two frequencies

1980 ◽  
Vol 31 (2) ◽  
pp. 269 ◽  
Author(s):  
CC Wong ◽  
JR Wilson
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Nitrogen Fertilizer ◽  
Light Extinction ◽  
Panicum Maximum ◽  
Nitrogen Accumulation ◽  
Nitrogen Status ◽  
Area Index ◽  
Full Sunlight ◽  
Nitrogen Yield

A study was made of the effect of illumination at 100, 60 and 40% of sunlight on the growth of Macroptilium atropurpureum cv. Siratro and Panicum maximum var. trichoglume cv. Petrie (green panic) in pure and 50150 mixture swards, dcfoliated every 4 (D4) 01 8 (D8) weeks. The plants were grown without nitrogen fertilizer on a soil of moderate nitrogen status. Shading to 60 and 40% of full sunlight increased the shoot yield of green panic in pure sward by 30 and 27% respectively in the D8, but reduced it in the D4 treatment by 3 and 14%. Shade (40% full sunlight) reduced the shoot yield of Siratro in pure swards by 38 and 33 % in the D4 and D8 treatments. Nitrogen accumulation in green panic was markedly improved by shading: the increase in shoot nitrogen yield in pure sward under 60 and 40% light levels was 29 and 32% for the D4 and 45 and 76 % for the D8 treatment. All plant fractions of green panic increased in percentage nitrogen with increasing shade. The nitrogen yield of Siratro in pure sward declined with shading in proportion to dry weight. Shaded green panic swards had a higher leaf area index, better distribution of leaf area with height, and lower light extinction coefficients. The individual leaves had greater photosynthetic activity than those from the full sunlight swards. Shade-grown Siratro swards had a lower leaf area index and their leaves had a lower photosynthetic potential than in the full sunlight treatment. Nodulation was reduced under shade. Competition between green panic and Siratro was most severe in relation to shoot yield, and was accentuated by shading, frequent defoliation, and time. The proportion of Siratro in the mixture declined from 40 % initially to as low as 4-6 %. The extra competitiveness of the tropical grass, green panic, under shade in this experiment was due to a substantially increased ability to accumulate nitrogen and also to changes in canopy structure. In soils of markedly different nitrogen status or with nitrogen fertilizer the shade response might be modified.

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