Effects of solar ultraviolet radiation on terrestrial ecosystems. Patterns, mechanisms, and interactions with climate change

Abstract

Ultraviolet radiation (UV) is a minor fraction of the solar spectrum reaching the ground surface. In this assessment we summarize the results of previous work on the effects of the UV-B component (280-315 nm) on terrestrial ecosystems, and draw attention to important knowledge gaps in our understanding of the interactive effects of UV radiation and climate change. We highlight the following points: (i) The effects of UV-B on the growth of terrestrial plants are relatively small and, because the Montreal Protocol has been successful in limiting ozone depletion, the reduction in plant growth caused by increased UV-B radiation in areas affected by ozone decline since 1980 is unlikely to have exceeded 6%. (ii) Solar UV-B radiation has large direct and indirect (plant-mediated) effects on canopy arthropods and microorganisms. Therefore, trophic interactions (herbivory, decomposition) in terrestrial ecosystems appear to be sensitive to variations in UV-B irradiance. (iii) Future variations in UV radiation resulting from changes in climate and land-use may have more important consequences on terrestrial ecosystems than the changes in UV caused by ozone depletion. This is because the resulting changes in UV radiation may affect a greater range of ecosystems, and will not be restricted solely to the UV-B component. (iv) Several ecosystem processes that are not particularly sensitive to UV-B radiation can be strongly affected by UV-A (315-400 nm) radiation. One example is the physical degradation of plant litter. Increased photodegradation (in response to reduced cloudiness or canopy cover) will lead to increased carbon release to the atmosphere via direct and indirect mechanisms.

UV-B effects on leaves—Oxidative stress and acclimation in controlled environments

“…However, because the recovery is slow and local UV conditions are expected to be modulated by various ozone modifying tropospheric conditions (for example clouds) and climate factors [49], research on plant acclimation strategies to supplemental UV-B is and will remain timely.…”

Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

“…The successful implementation of the Montreal protocol decelerated the weakening of the ozone layer (Egorova et al, 2013;Mäder et al, 2010;Newman and McKenzie, 2011) and many recent studies indicate the first signs of recovery over the Northern Hemisphere (Kuttippurath et al, 2013;McLinden and Fioletov, 2011;Newchurch et al, 2003;Smedley et al, 2012). Signs from the onset of ozone recovery since the late 1990s on surface UV-B irradiance have been mainly detected over the northern high latitudes; recent studies indicate that UV-B has been declining during the last 2 decades (Bernhard, 2011;Eleftheratos et al, 2014). However, during the same period, both the UV-B and the UV-A irradiance are increasing over many locations in the Northern Hemisphere mid-latitudes, mainly due to the negative trends in the amount of clouds and aerosols (De Bock et al, 2014;Fitzka et al, 2012;Román et al, 2015;Smedley et al, 2012;Zerefos et al, 2012).…”

Photodegradation alleviates the lignin bottleneck for carbon turnover in terrestrial ecosystems

“…In addition, for historical reasons related to studies of the effects of stratospheric ozone depletion (29,30), there has been a strong emphasis on evaluating the effects of UV (200-400 nm) radiation (particularly UV-B, 280-315 nm) on litter decomposition, and these studies have yielded equivocal results with respect to the importance of this spectral region as a driver of photodegradation (31,32). Recent evidence has demonstrated that the visible component of sunlight [blue and green wavelengths, 400-550 nm (BG)] can have a large impact on photodegradation (17,20), suggesting…”