A spectral weighting function for abiotic photodegradation based on photochemical emission of CO2 from leaf litter in sunlight
- 46 Downloads
Photodegradation can be a significant driver of leaf litter decomposition although the spectral effectiveness of sunlight in driving this process is not well characterized. We developed spectral weighting functions (WFs) for the photochemical emission of CO2 from three leaf litter types using 10 cutoff filters that provided contrasting polychromatic sunlight under clear skies in Tempe, AZ, USA. An iterative nonlinear least-squares regression fitting procedure was used to estimate how effective sunlight at a given wavelength was in eliciting CO2 emission. Although absolute CO2 emission rates varied appreciably among litter types, their WFs were very similar. Using the average WF of all litter types, the effectiveness of sunlight declined from 300 nm by one and two orders of magnitude at 399 and 498 nm, respectively. The slope of the WF was most similar to WFs for CO emission from terrestrial leaf litter and photobleaching of dissolved organic matter in lakes, and was much more gradual than WFs addressing UV damage to biotic processes. Peak effectiveness of clear-sky noon sunlight with our WF occurred at 330 nm, with UV-B (280–320 nm), UV-A (320–400 nm) and visible (400–550 nm) wavebands responsible for 9, 61 and 30% of CO2 emission, respectively. Results from past field studies suggest that solar UV is typically less effective in driving litter mass loss than our WF predicts; we discuss possible reasons for this discrepancy. The gradual slope of our WF implies that differences in UV-B irradiance associated with stratospheric ozone thickness or latitude are unlikely to significantly influence photochemical litter emission.
KeywordsAction spectra Litter decomposition Photodegradation Photomineralization UV radiation Visible radiation
We thank Dr. Gunnar W. Schade, Department of Atmospheric Sciences, Texas A&M University, for providing data for his action spectra of CO emission from leaves. This work was supported by the National Science Foundation under grant DEB-1256180 to TAD. The authors declare no conflict of interest.
- Aphalo PJ, Albert A, Björn LO, Ylianttila L, Figueroa FL, Huovinen P (2012) Introduction. In: Aphalo PJ, Albert A, Björn LO, McLeod A, Robson TM, Rosenqvist E (eds) Beyond the visible: a handbook of best practice in plant UV photobiology. COST action FA0906 UV4growth. University of Helsinki, Helsinki, pp 1–33Google Scholar
- Barnes PW, Throop HL, Archer SR, Breshears DD, McCulley RL, Tobler MA (2015) Sunlight and soil–litter mixing: drivers of litter decomposition in drylands. Prog Bot 76:273–302Google Scholar
- Brandt LA, Bohnet C, King JY (2009) Photochemically induced carbon dioxide production as a mechanism for carbon loss from plant litter in arid ecosystems. J Geophys Res 114:1–13Google Scholar
- Caldwell MM, Camp LB, Warner CW, Flint SD (1986) Action spectra and their key role in assessing biological consequences of solar UV-B radiation change. In: Worrest RC, Caldwell MM (eds) Stratospheric ozone reduction, solar ultraviolet radiation and plant life. Springer, Berlin, pp 87–111CrossRefGoogle Scholar
- Cullen JJ, Neale PJ (1997) Biological weighting functions for describing the effects of ultraviolet radiation on aquatic systems. In: Hader DP (ed) The effects of ozone depletion on aquatic ecosystems. Academic Press, San Diego, pp 97–118Google Scholar
- Mikkelsen TN, Bruhn D, Ambus P (2016) Solar UV irradiation-induced production of greenhouse gases from plant surfaces: from leaf to earth. Prog Bot 78:407–437Google Scholar
- Osburn CL, Morris DP (2003) Photochemistry of chromophoric dissolved organic matter in natural waters. In: Helbling EW, Horacio Zagarese H (eds) UV effects in aquatic organisms and ecosystems. The Royal Society of Chemistry. Springer, Cambridge, pp 185–217Google Scholar
- Rutledge S, Campbell DI, Baldocchi D, Schipper LA (2010) Photodegradation leads to increased carbon dioxide losses from terrestrial organic matter. Glob Change Biol 16:3065–3074Google Scholar