Latitude and Weather Influences on Sun Light Quality and the Relationship to Tree Growth

Abstract

Natural changes in photoperiod, light quantity, and quality play a key role in plant signaling, enabling daily and seasonal adjustment of growth and development. Growing concern about the global climate crisis together with scattered reports about the interactive effects of temperature and light parameters on plants necessitates more detailed information about these effects. Furthermore, the actual light emitting diode (LED) lighting technology allows mimicking of light climate scenarios more similar to natural conditions, but to fully exploit this in plant cultivation, easy-to-apply knowledge about the natural variation in light quantity and spectral distribution is required. Here, we aimed to provide detailed information about short and long-term variation in the natural light climate, by recording the light quantity and quality at an open site in Switzerland every minute for a whole year, and to analyze its relationship to a set of previous tree seedling growth experiments. Changes in the spectral composition as a function of solar elevation angle and weather conditions were analyzed. At a solar elevation angle lower than 20°, the weather conditions have a significant effect on the proportions of blue (B) and red (R) light, whereas the proportion of green (G) light is almost constant. At a low solar elevation, the red to far red (R:FR) ratio fluctuates between 0.8 in cloudy conditions and 1.3 on sunny days. As the duration of periods with low solar angles increases with increasing latitude, an analysis of previous experiments on tree seedlings shows that the effect of the R:FR ratio correlates with the responses of plants from different latitudes to light quality. We suggest an evolutionary adaptation where growth in seedlings of selected tree species from high latitudes is more dependent on detection of light quantity of specific light qualities than in such seedlings originating from lower latitudes.

Alpine and Polar Treelines in a Changing Environment

“…Apart from altitude, these maps also take into account micro-relief, slope, and aspect. Chiang et al [16] proposed that aside from temperature, potential changes in light quality and quantity also play an important role in the phenology and growth of woody plants in boreal and temperate climates.…”

Does drought advance the onset of autumn leaf senescence in temperate deciduous forest trees?

“…Deciduous trees therefore seem to have a conservative strategy concerning the timing of their autumn leaf senescence that might be under the control of a constant variable (e.g. the day-length or photo spectrum) (Michelson et al, 2018;Chiang et al, 2019). Such a strategy prioritizes carbon uptake over nutrient remobilization, as a fixed onset of autumn leaf senescence would not allow an advanced nutrient remobilization when required (Keskitalo et al, 2005;Brelsford et al, 2019).…”

“…As there is very little difference in the light conditions among the different sites, the difference in the day length is unlikely to have affected the difference in the timing of the onset of autumn leaf senescence between the beech saplings and mature trees. However, it is possible that the beech saplings have a different sensitivity to the light cues, as they usually grow in the understory and therefore under a different light regime than mature trees (Brelsford et al, 2019;Michelson et al, 2018;Chiang et al, 2019). Concerning the onset of the loss of canopy greenness for all species and opposed to 2017 (i.e.…”

Reaching Natural Growth: Light Quality Effects on Plant Performance in Indoor Growth Facilities

“…Similar results have been reported at 15–30% B compared with 50% B [ 8 ]. This effect may indicate the evolutionary adaption of species to the natural sunlight spectrum, with higher quantum yield under a more natural B:R ratio (circa 33% of B in the sunlight spectrum [ 36 ]). Other conditions with extreme levels of B or R light may require the adaptation to each light condition, where CO 2 fixation may have a wavelength dependence related to absorption properties of the different pigments involved.…”

“…To unify nomenclature with previous studies, the four different light treatments will be referred to by their respective B light proportion ( Table 1 ). The light treatments were chosen based on previous literature (e.g., Hogewoning et al [ 8 ]), measurements of natural light completed in situ [ 36 ], and technical capacities of the phytotrons at the average light intensity of the outdoor treatment. For each treatment, the replication per species was 9 pots (with either one or more individuals per pot depending on species; see above).…”