Effects of UV radiation and rainfall reduction on leaf and soil parameters related to C and N cycles of a Mediterranean shrubland before and after a controlled fire
Background and aims
In the Mediterranean basin, reduction in cloudiness owing to climate change is expected to enhance solar ultraviolet (UV) levels and to decrease rainfall over the coming years, which would be accompanied by more frequent and intense wildfires. The aim of the present study was to investigate the role of solar UV-A and UV-B radiation in C and N pools of a Mediterranean shrubland and whether drier conditions could alter this role before and after a fire.
Over a three-year field experiment, 18 plots of 9 m2 were subjected to three UV conditions (UV-A + UV-B exclusion, UV-B exclusion or near-ambient UV-A + UV-B exposure) combined with two rainfall regimes (natural or reduced rainfall). Several parameters related to C and N cycles in the soil and in the leaves and litter of two dominant plant species (Arbutus unedo and Phillyrea angustifolia) were measured before and after an experimental fire.
UV-A exposure increased soil moisture throughout the study period, as well as respiration before the fire. The additional presence of UV-B decreased β-glucosidase activity at 5–10 cm depth and soil respiration and pH. UV-B exposure also raised leaf C concentration in P. angustifolia and δ15N values in A. unedo. Reduced rainfall often emphasized the opposite effects of UV-A and UV-B on the studied parameters. After the fire, most of the UV and rainfall effects were lost.
UV-A exposure seems to stimulate soil biological activity and, thus, C and N turn-over, while the effect of UV-B would be the opposite. At least in the short term, the “homogenizing influence” of fire would probably have a stronger effect on the C and N cycles than the expected changes in UV and rainfall levels.
KeywordsCarbon cycle Drought Fire Mediterranean shrublands Nitrogen cycle UV radiation
This research was supported by the Spanish Government (CGL2010-22283 and CGL2014-55976-R) and the University of Girona (ASING2011/3 and MPCUdG2016). We are grateful to the Gavarres Consortium for allowing us to perform the experiment in Can Vilallonga. We also thank Jordi Compte, Meritxell Bernal and Miquel Jover for their help with the field experiment, and Dr. Alan Jones for his comments to improve the manuscript.
- Castaldi S, Carfora A, Fiorentino A et al (2009) Inhibition of net nitrification activity in a Mediterranean woodland: possible role of chemicals produced by Arbutus unedo. Plant Soil 315:273–283. https://doi.org/10.1007/s11104-008-9750-x
- Castells E, Peñuelas J, Valentine DW (2004) Are phenolic compounds released from the Mediterranean shrub Cistus albidus responsible for changes in N cycling in siliceous and calcareous soils? New Phytol 162:187–195. https://doi.org/10.1111/j.1469-8137.2004.01021.x
- Day TA, Zhang ET, Ruhland CT (2007) Exposure to solar UV-B radiation accelerates mass and lignin loss of Larrea tridentata litter in the Sonoran Desert. Plant Ecol 193:185–194. https://doi.org/10.1007/s11258-006-9257-6
- Díaz-Delgado R, Lloret F, Pons X, Terradas J (2002) Satellite evidence of decreasing resilience in Mediterranean plant communities after recurrent wildfires. Ecology 83:2293–2303. https://doi.org/10.1890/0012-9658(2002)083[2293:SEODRI]2.0.CO;2 CrossRefGoogle Scholar
- El Omari B, Fleck I, Aranda X et al (2003) Total antioxidant activity in Quercus ilex resprouts after fire. Plant Physiol Biochem 41:41–47Google Scholar
- Erickson AJ, Ramsewak RS, Smucker AJ, Nair MG (2000) Nitrification inhibitors from the roots of Leucaena leucocephala. J Agric Food Chem 48:6174–6177. https://doi.org/10.1021/jf991382z
- Flint SD, Caldwell MM (2003) Field testing of UV biological spectral weighting functions for higher plants. Physiol Plant 117:145–153. https://doi.org/10.1034/j.1399-3054.2003.1170118.x CrossRefGoogle Scholar
- Forster J (1995) Soil physical analysis. In: Alef K, Nannipieri P (eds) Methods in Soil Microbiology and Biochemistry. Academic Press, London, pp 79–87 105–121Google Scholar
- Hofmann RW, Campbell BD, Bloor SJ et al (2003) Responses to UV-B radiation in Trifolium repens L. – physiological links to plant productivity and water availability. Plant Cell Environ 26:603–612. https://doi.org/10.1046/j.1365-3040.2003.00996.x
- Högberg P, Johannisson C, Högberg MN (2014) Is the high 15N natural abundance of trees in N-loaded forests caused by an internal ecosystem N isotope redistribution or a change in the ecosystem N isotope mass balance? Biogeochemistry 117:351–358. https://doi.org/10.1007/s10533-013-9873-x CrossRefGoogle Scholar
- IPCC (2013) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, and New YorkGoogle Scholar
- Llorens L, Peñuelas J, Estiarte M (2003) Ecophysiological responses of two Mediterranean shrubs, Erica multiflora and Globularia alypum, to experimentally drier and warmer conditions. Physiol Plant 119:231–243. https://doi.org/10.1034/j.1399-3054.2003.00174.x
- Lu Y, Duan B, Zhang X et al (2009) Intraspecific variation in drought response of Populus cathayana grown under ambient and enhanced UV-B radiation. Ann For Sci 66:613–624. https://doi.org/10.1051/forest/2009049
- Masciandaro G, Ceccanti B, García C (1994) Anaerobic digestion of straw and piggery wastewaters II. Optimization of the process. Agrochimica 38:195–203Google Scholar
- Nannipieri P, Kandeler E, Ruggiero P (2002) Enzyme activities and microbiological and biochemical processes in soil. In: Burns RG, Dick RP (eds) Enzymes in the environment: activity, ecology and applications. Marcel Dekker, New York, pp 1–33Google Scholar
- Nenadis N, Llorens L, Koufogianni A et al (2015) Interactive effects of UV radiation and reduced precipitation on the seasonal leaf phenolic content/composition and the antioxidant activity of naturally growing Arbutus unedo plants. J Photochem Photobiol B Biol 153:435–444. https://doi.org/10.1016/j.jphotobiol.2015.10.016
- Riera P, Peñuelas J, Farreras V, Estiarte M (2007) Valuation of climate-change effects on Mediterranean shrublands. Ecol Appl 17:91–100. https://doi.org/10.1890/1051-0761(2007)017[0091:VOCEOM]2.0.CO;2 CrossRefPubMedGoogle Scholar
- Savé R, Alegre L, Pery M, Terradas J (1993) Ecophysiology of after-fire resprouts of Arbutus unedo L. Orsis 8:107–119Google Scholar
- Soil Survey Staff (2010) Keys to soil taxonomy. Eleventh, USDA-NRCS, Washington, DCGoogle Scholar
- Tárrega R, Luis-Calabuig E, Valbuena L (2001) Eleven years of recovery dynamic after experimental burning and cutting in two Cistus communities. Acta Oecol 22:277–283. https://doi.org/10.1016/S1146-609X(01)01125-0
- Verdaguer D, Ojeda F (2002) Root starch storage and allocation patterns in seeder and resprouter seedlings of two cape Erica (Ericaceae) species. Am J Bot 89:1189–1196. https://doi.org/10.3732/ajb.89.8.1189