Recent field experiments show how photodegradation and its legacy, increased microbial access to labile carbohydrates (photofacilitation), double rates of C loss to the atmosphere in a Mediterranean-type climate. The mechanisms demonstrated have implications for global C modeling beyond Mediterranean ecosystems.Fil: Pérez Harguindeguy, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

Pérez Harguindeguy, Natalia

Current Biology

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11. Leca, J.-B. (2015). Arbitrary cultural behaviorpatterns are not unique to humans. Curr.Anthropol. 56, 112–113.12. Mazerolle, D.F., Hobson, K.A., andWassenaar, L.I. (2005). Stable isotope andband-encounter analysis delineate migratorypatterns and catchment areas of white-throated sparrows at a migration monitoringstation. Oecologia 144, 541–549.13. DeWolfe, B.B., and Baptista, L.F. (1995).Singing behavior, song types on their winteringgrounds and the question of leap-frogmigration in puget sound white-crownedsparrows. Condor 97, 376–389.14. Searcy, W.A., Anderson, R.C., and Nowicki, S.(2006). Bird song as a signal ofaggressive intent. Behav. Ecol. Sociobiol. 60,234–241.15. Celis-Murillo, A., Stodola, K.W., Pappadopoli,B., Burton, J.M., and Ward, M.P. (2016).Seasonal and daily patterns of nocturnalsinging in the Field Sparrow (Spizella pusilla).J. Orn. 157, 853–860.16. Odom, K.J., Hall, M.L., Riebel, K., Omland,K.E., and Langmore, N.E. (2014). Female songis widespread and ancestral in songbirds. Nat.Commun. 5, 3379.17. Kaluthota, C., Brinkman, B.E., dos Santos,E.B., and Rendall, D. (2016). Transcontinentallatitudinal variation in song performance andcomplexity in house wrens (Troglodytesaedon). Proc. R. Soc. B 283, 20152765.18. Anderson, B.L. (2008). Migration,Accommodation, and Language Change:Language at the Intersection of Regional andEthnic Identity (New York: PalgraveMacMillan).19. Noad, M.J., Cato, D.H., Bryden, M.M., Jenner,M.N., and Jenner, K.C. (2000). Culturalrevolution in whale songs. Nature 408, 537.20. Allen, J.A., Garland, E.C., Dunlop, R.A., andNoad, M.J. (2018). Cultural revolutions reducecomplexity in the songs of humpback whales.Proc. R. Soc. B 285, 20182088.llDispatchesEcology: The Patagonian Sun DanceNatalia Perez HarguindeguyFacultad de Cs. Exactas, Fı́sicas y Naturales (Universidad Nacional de Córdoba) and Instituto Multidisciplinario de Biologı́a Vegetal(CONICET-UNC), 5000 Córdoba, ArgentinaCorrespondence: natalia.perez.h@unc.edu.arhttps://doi.org/10.1016/j.cub.2020.06.066Recent field experiments show how photodegradation and its legacy, increased microbial access to labilecarbohydrates (photofacilitation), double rates of C loss to the atmosphere in a Mediterranean-typeclimate. The mechanisms demonstrated have implications for global C modeling beyond Mediterraneanecosystems.Probably before preschool, we learn thatsunlight is the fundamental energysource upon which life is built on thisplanet. Usually, later, we learn that thetransformation of that energy in life,which starts with photosynthesis, endsits cycle in decomposition, thebreakdown of dead beings. What is not inthe common knowledge of kids is thatsunlight can also play a role in thebreakdown and decay of organic matter.Somehow, this gap in children’s worldview replicates the state of scientificknowledge—we understand much moreabout photosynthesis and productivitythan we understand aboutdecomposition in general, and the effectof sunlight on organic matter breakdownin particular. In fact, the effect of sunlightin breaking down matter, and itsconsequences on the C balance, has notreached mainstream attention until thelast few decades. Now, we know thatsunlight can have direct or abiotic effects(photodegradation or photolysis) onorganic matter breakdown. In addition,sunlight can have indirect or bioticeffects (photofacilitation orphotopriming), a result of the activity ofdecomposers on the chemical changesdriven by previous photodegradation.We also know that these processes canhave a significant role in C dynamics, inboth aquatic and terrestrial systems[1–3]. Based on some mechanisticunderstanding of those relationships,biogeochemical models have started toincorporate these processes [4].However, to develop realistic modelsthat fully account for the role of exposureto sunlight in the C cycle, we need agreater comprehension of the driversbehind and beyond this process, as wellas how it can vary depending on thesubstrate, the climate and thedecomposer communities [3].Building on previous findings (e.g.[2,5,6]), a new article from Berenstecherand colleagues in this issue of CurrentBiology [7] presents strong andconsistent evidence on the direct(photodegradation) and indirectCurrent Biology 30, R932–R961,(photofacilitation) effect of solar radiationon C cycling in a Mediterranean-typeecosystem. Based on a combination ofcomplementary field manipulations,Berenstecher and colleaguesdemonstrate how the effect of sunlightcan have a much higher impact on Crelease than previously detected, whenphotodegradation during the dry summerseason is combined with the facilitation ofbiotic decomposition — throughincreased accessibility of litterpolysaccharides — during the wet winter.Although these findings partially coincidewith previous work, the experimentaldesign of Berenstecher and colleaguesgives us some hints on why, and how, themain drivers of decomposition swing fromabiotic to biotic through the seasons ofMediterranean climate in Patagonia, asthe effects of sunlight cross seasons(Figure 1).The role of solar radiation ondecomposition was proposed as arelevant process in the context of aridecosystems more than 50 years ago [8].August 17, 2020 ª 2020 Elsevier Inc. R959Dry summer Wet winter Dry summer Wet winterBiota &photofacilitationBiota &photofacilitationTree(Nothofagus)Grass(Pappostipa)Aphyllous shrub(Mulinum)Mass loss increaseLignin decreasePolysaccharide accessibilityincreasePhotodegradation PhotodegradationCurrent BiologyFigure 1. The cycle of sunlight-mediated degradation in a Mediterranean climate inPatagonia.Thedrawing represents, frombottom to top: bottom: climatic oscillations in temperature (reddish line), rainfall(bluish line) and solar radiation (yellowish line) along 2 years in the Mediterranean climate Patagonia. Middle:the three growth forms ‘leaves’ used in the experiment (tree, grass, and aphyllous shrub) which, from left toright, decrease in size and definition representing changes in litter mass and in litter chemistry (decreasedlignin content and increased accessibility to polysaccharides). Top: the seasons in which the effects ofsunlight (photodegradation) not only dominate the dry summer but also ‘permeate’ in the wet winter(through the interaction of photofacilitation with biota). Artwork from Ma. Cristina Montes.llDispatchesHowever, only in the last 15 years has itgained wider attention [3,9]. Initially,research into sunlight effects ondecomposition was linked to the impactsof increased ultraviolet-B (UV-B) radiationas a result of ozone depletion in the 1980s[10]. Then, the main effects proposed forR960 Current Biology 30, R932–R961, AugusUV-B radiation were indirect(photofacilitation and negative impacts onmicrobial communities), while theecosystems studied were those of highlatitudes [11,12]. The interest in UV-Bradiation has continued until present, asmost plant compounds have a maximumt 17, 2020absorbance in its range. However, now,we have multiple lines of evidence thatUV-A (315–400 nm) and blue-green visibleradiation (420–570 nm) may have an evengreater role in decomposition than UV-B[5,13,14]. This is because, as most ofUV-B is filtered by the atmosphere,there is much more UV-A and visibleradiation reaching plant tissues thanUV-B. Consequently, these wavelengthshave been estimated to be responsiblefor 90% of the photochemical CO2emission [15].Using full-sunlight field studies,Berenstecher and colleagues first showus how exposure to dry summer fullsunlight can double litter mass lossacross species of different quality, andindependently of that litter quality, whilebiotic activity becomes the main driver ofdecomposition during the wet winterwhen differences in decompositionamong species do relate to litter quality.These results provide strong field supportfor earlier findings [5,6] and constitute thebasis on which the authors discriminatethe effects of sunlight and biota insubsequent experiments.In the second set of experiments,Berenstecher and colleaguesdemonstrate that, when leaf litter isexposed to full solar radiation during thedry summer, it decomposes faster duringthe wet winter (up to 100% faster, for thegrass litter) than leaf litter that startsdecomposition during the wet winter. Thispattern is associated with a higheravailability of polysaccharides in the litterthat started its decomposition during thedry summer, as well as with a decrease inits lignin content. What is even moreinteresting is how the complementaryexperiments at the same time separateand integrate two of the main pathwaysby which sunlight interacts with leaf litterand biota on decomposition. By doing so,Berenstecher and colleagues defy thenotion that experiments in naturalconditions could hinder ourunderstanding of sunlight’s effects ondecomposition becausephotodegradation and photofacilitationcannot be entirely distinguished [5,16].In the third concatenated experiment,Berenstecher and colleagues take on thetask of integrating the sunlight and biotaeffects over the long-term, a needsystematically emphasized in theecological literature. The results of thellDispatchescombined effects of solar exposure andbiota over 2 years under the dry summersand wet winters of Patagonia show thatsolar radiation becomes themain driver ofdecomposition, doubling decompositioncompared with attenuated radiationtreatments. This strong effect could berelated to the length of the experimentin combination with the fact that fullsunlight was reaching leaf litter — thecombination of these two experimentalcharacteristics is difficult to find in fieldexperiments.The idea of sunlight breaking downmaterial, either organic or inorganic,through different pathways is notabsolutely new, particularly for aridecosystems. Nevertheless, ourunderstanding of the different andinteracting effects of sunlight on C andnutrient cycling is fragmented, andresearch is still rather restricted toparticular ecosystems. The findings ofBerenstecher et al., in the context ofrecent studies showing photodegradationand photofacilitation operating in cold,mesic, temperate and tropicalecosystems [17–20], expand the skiesunder which sunlight might be directly orindirectly driving decomposition.Although we are still far from having aclear picture of how the multiple effects ofsunlight drive, or interact with the driversof, the dynamics of growth anddecomposition across time and space,these recent findings should motivate usto broaden our exploration of sunlighteffects to any systems in which leaf litteris, at least seasonally, exposed to highsunlight. The integration of recentliterature would indicate that, if there issunlight, there are sunlight effects.REFERENCES1. Anesio, A.M., Tranvik, L.J., and Graneli, W.(1999). Production of inorganic carbon fromaquatic macrophytes by solar radiation.Ecology 80, 1852–1859.2. Austin, A.T., and Vivanco, L. (2006). Plant litterdecomposition in a semi-arid ecosystemcontrolled by photodegradation. Nature 442,555–558.3. Austin, A.T. (2011). Has water limited ourimagination for aridland biogeochemistry?Trends Ecol. Evol. 26, 229–235.4. King, J.Y., Brandt, L.A., and Adair, E.C. (2012).Shedding light on plant litter decomposition:Advances, implications and new directions inunderstanding the role of photodegradation.Biogeochemistry 111, 57–81.5. Foreid, B., Rivero, M.J., Primo, O., and Ortiz, I.(2011). Modelling photodegradation in theglobal carbon cycle. Soil Biol. Biochem. 43,1383–1386.6. Austin, A.T., Mendez, M.S., and Ballare, C.L.(2016). Photodegradation alleviates the ligninbottleneck for carbon turnover in terrestrialecosystems. Proc. Natl. Acad. Sci. USA 113,4392–4397.7. Berenstecher, P., Vivanco, L., Perez, L.I.,Ballare, C.L., and Austin, A.T. (2020). Sunlightdoubles aboveground carbon loss in aseasonally dry woodland in Patagonia. Curr.Biol. 30, 3243–3251.8. Mendez, M.S., Martinez, M.L., Araujo, P.I., andAustin, A.T. (2019). Solar radiation exposureaccelerates decomposition and biotic activityin surface litter but not soil in a semiaridwoodland ecosystem in Patagonia, Argentina.Plant Soil 445, 483–496.9. Pauli, F. (1964). Soil fertility problem in arid andsemi-arid lands. Nature 204, 1286–1288.10. Zepp, R.G., Erickson, D.J., Paul, N.D., andSulzberger, B. (2011). Effects of solar UVradiation and climate change onbiogeochemical cycling; interactions andfeedbacks. Photochem. Photobiol. Sci. 10,261–279.11. Paul, N.D., Callaghan, T., Moody, S.A., Gwynn-Jones, D., Johanson, U., and Gehrke, C. (1999).Current BiolUV-B impacts on decomposition andbiogeochemical cycling. InStratosphericOzoneDepletion: The Effects of Enhanced UV-BRadiation on Terrestrial Ecosystems, J.Rozema, ed. (Leiden: Backhuys Publishers),pp. 117–133.12. Paul, N.D., and Gwynn-Jones, D. (2003).Ecological roles of solar UV radiation: towardsan integrated approach. Trends Ecol. Evol. 18,48–55.13. Austin, A.T., and Ballare, C.L. (2010). Dual roleof lignin in plant litter decomposition interrestrial ecosystems. Proc. Natl. Acad. Sci.USA 107, 4618–4622.14. Brandt, L.A., Bohnet, C., and King, J.Y. (2009).Photochemically induced carbon dioxideproduction as a mechanism for carbon lossfrom plant litter in arid ecosystems.J. Geophys. Res.-Biogeosci. 114, G02004.15. Day, T.A., and Bliss, M.S. (2019). A spectralweighting function for abioticphotodegradation based on photochemicalemission of CO2 from leaf litter in sunlight.Biogeochemistry 146, 173–190.16. Gliksman, D., Haenel, S., and Grünzweig, J.M.(2018). Biotic and abiotic modifications of leaflitter during dry periods affect litter mass lossand nitrogen loss during wet periods. Funct.Ecol. 32, 831–839.17. Brandt, L.A., King, J.Y., Hobbie, S.E., et al.(2010). The role of photodegradation in surfacelitter decomposition across a grasslandecosystem precipitation gradient. Ecosystems13, 765–781.18. Liu, G., Wang, L., Jiang, L., Pan, X., Huang, Z.,Dong, M., and Cornelissen, J.H.C. (2018).Specific leaf area predicts dryland litterdecomposition via two mechanisms. J. Ecol.106, 218–229.19. Pieriste, et al. (2019). Solar UV-A radiation andblue light enhance tree leaf litterdecomposition in a temperate forest.Oecologia 191, 191–203.20. Marinho, O.A., Martinelli, L.A., Duarte-Neto,P.J., Mazzi, E.A., and King, J.Y. (2020).Photodegradation influences litterdecomposition rate in a humid tropicalecosystem, Brazil. Sci. Total Environ. 715,136601.ogy 30, R932–R961, August 17, 2020 R961

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Ecology: The patagonian sun dance

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Ecology: The patagonian sun dance

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