Mapping Monthly Distribution of Daily Light Integrals across the Contiguous United States

Abstract

<jats:p>The daily light integral (DLI) is a measurement of the total amount of photosynthetically active radiation delivered over a 24-hour period and is an important factor influencing plant growth over weeks and months. Contour maps were developed to demonstrate the mean DLI for each month of the year across the contiguous United States. The maps are based on 30 years of solar radiation data for 216 sites compiled and reported by the National Renewable Energy Lab in radiometric units (watt-hours per m<jats:sup>-2</jats:sup>·d<jats:sup>-1</jats:sup>, from 300 to 3,000 nm) that we converted to quantum units (mol·m<jats:sup>-2</jats:sup>·d<jats:sup>-1</jats:sup>, 400 to 700 nm). The mean DLI ranges from 5 to 10 mol·m<jats:sup>-2</jats:sup>·d<jats:sup>-1</jats:sup> across the northern U.S. in December to 55 to 60 mol·m<jats:sup>-2</jats:sup>·d<jats:sup>-1</jats:sup> in the southwestern U.S. in May through July. From October through February, the differences in DLI primarily occur between the northern and southern U.S., while from May through August the differences in DLI primarily occur between the eastern and western U.S. The DLI changes rapidly during the months before and after the vernal and autumnal equinoxes, e.g., increasing by more than 60% from February to April in many locations. The contour maps provide a means of estimating the typical DLI received across the U.S. throughout the year.</jats:p>

Seduced by the dark side: integrating molecular and ecological perspectives on the influence of light on plant defence against pests and pathogens

“…Although photosynthesis is a function of irradiance, growth is determined by the sum of photosynthetic carbon fixation over time which is, in turn, a function of the amount of light received by the plant over that period. Thus, growth and yield, and many other long‐term effects of light, are best described by the accumulated dose of photosynthetic radiation, for example by daily light integral (Kitaya et al ., 1998; Korczynski et al ., 2002; Dielen et al ., 2004). Light damage is also often a function of accumulated dose, as with many whole‐plant responses to UV radiation (Gonzalez et al ., 1998; de la Rosa et al ., 2001).…”

Comparative Performance and Daily Light Integral Requirements of Warm‐Season Turfgrasses in Different Seasons

“…The average monthly DLI for the United States ranges from 55 to 60 mol m −2 d −1 in the southwest during the summer months and 5 to 10 mol m −2 d −1 in the north during the winter months (Korczynski et al, 2002). As a measure of the total quantity of photosynthetically active photons delivered over the course of an entire day, daily light integral (DLI, mol m −2 d −1 ), can be used to indicate the light intensity requirement of a cultivar to maintain an acceptable TQ.…”

“…As a measure of the total quantity of photosynthetically active photons delivered over the course of an entire day, daily light integral (DLI, mol m −2 d −1 ), can be used to indicate the light intensity requirement of a cultivar to maintain an acceptable TQ. The average monthly DLI for the United States ranges from 55 to 60 mol m −2 d −1 in the southwest during the summer months and 5 to 10 mol m −2 d −1 in the north during the winter months (Korczynski et al, 2002). Selection of turfgrass species and cultivars could be improved by measuring the DLI of a particular location and knowing the optimum DLI requirement for each.…”

An introduction toOplismenus undulatifolius(Ard.) Roem. & Schult. (wavyleaf basketgrass), a recent invader in Mid-Atlantic forest understories1,2

“…The maximum canopy openness recorded was 27%, and the highest transmitted light levels were 11.3 mols m 22 day 21 . In full sun, transmitted light (measured as the daily light integral of photosynthetically active radiation) ranges from 35-45 mols m 22 day 21 in the Mid-Atlantic Region in July and August (Korczynski et al 2002). In an experiment with shade tolerant bedding species used in the nursery trade, plants grew poorly at light levels below 5 mols m 22 day 21 , with steady improvements in plant quality up through 20 mols m 22 day 21 (Holcombe et al 2001).…”