Effect of Sunlight on Decomposition of Soil Humic and Non-Humic Fractions
Keywords:
Humic, Non-humic, Global warming, Sunlight, Photodecomposition, Thermal effect
Abstract
Soils function as huge carbon sinks, storing more than twice the atmospheric C. The contributions of soil organic carbon (SOC) to global warming have mainly focused on the effect of biotic factors that are accelerated by temperature rise. Recently we demonstrated that sunlight causes significant reduction in soil organic matter (SOM). In this study, we recorded the changes in the two main fractions, humic and non-humic components of SOM under the influence of sunlight and UV light. Photodecomposition losses are higher in non-humic compared to the humic fraction. Forest soils have higher contents and proportionately larger amounts of non-humic fraction that are more rapidly decomposed. Therefore, deforestation could be a significant source of atmospheric CO2 adding about 1x104 kg of CO2 annually, for every hectare of land that is deforested. Both thermal (heat) as well as photolytic (light) effects of sunlight cause decomposition losses of humic and non-humic fractions; however, proportionately, more humic fraction is decomposed by light while non-humic fraction is more affected by heat. Increase in pH causes greater photodecomposition of both humic and non-humic fractions. We conclude that sunlight needs to be considered as an important causative agent of global warming, with maximum contributions from the non-humic component of SOM.References
Ahmed N, Varadachari C and Ghosh K (2002) Soil clay-humus complexes. I. Alkali dissolution, TEM and XRD studies Aust J Soil Res 40 691-703.
Allard B, Borén H, Pettersson C and Zhang G (1994) Degradation of humic substances by UV irradiation Environ Int 20 97-101.
Batjes N H (2014) Total carbon and nitrogen in the soils of the world Eur J Soil Sci 65 4-21
Bellamy P H, Loveland P J, Bradley R I, Murray Lark R and Krick G (2005) Carbon losses from all soils across England and Wales 1978-2003 Nature 437 245-248.
Bond-Lamberty B and Thomson A (2010) Temperature-associated increases in the global soil respiration record Nature 464 579-582.
Chen Y, Khan S U and Schnitzer M (1978) Ultraviolet irradiation of dilute fulvic acid solutions Soil Sci Soc Am J 41 292- 296.
Crowther, T W and 49 others (2016) Quantifying global soil carbon losses in response to warming Nature 540 104-108.
Davidson E A and Janssens I A (2006) Temperature sensitivity of soil carbon decomposition and feedbacks to climate change Nature 440 165-173.
Moran A M and Zeep G R (2000) Carbon loss and optical property changes during long term photochemical and biological degradation of estuarian dissolved organic matter Limnol Oceanogr 45 1254-1264.
Nelson D W and Sommers L E (1996) Total carbon, organic carbon, and organic matter. In: Methods of Soil Analysis, Part 3 (Sparks, D L, ed.) pp 961-1010, Soil Science Society of America, Madison, Wisc.
Saikh H, Varadachari C and Ghosh K (1998) Changes in carbon, nitrogen and phosphorus levels due to deforestation and cultivation: A case study in Simlipal National Park, India Pl Soil 198 137-145.
Varadachari C, Mitra S and Ghosh K (2017) Photochemical oxidation of soil organic matter by sunlight Proc Indian Natn Sci Acad 83 223-229.
Zeep R G, Braun A M, Hoigne J and Leenheer J A (1987) Photoproduction of hydrated electrons from natural organic solutes in aquatic environment Environ Sci Technol 21 443-450.
Allard B, Borén H, Pettersson C and Zhang G (1994) Degradation of humic substances by UV irradiation Environ Int 20 97-101.
Batjes N H (2014) Total carbon and nitrogen in the soils of the world Eur J Soil Sci 65 4-21
Bellamy P H, Loveland P J, Bradley R I, Murray Lark R and Krick G (2005) Carbon losses from all soils across England and Wales 1978-2003 Nature 437 245-248.
Bond-Lamberty B and Thomson A (2010) Temperature-associated increases in the global soil respiration record Nature 464 579-582.
Chen Y, Khan S U and Schnitzer M (1978) Ultraviolet irradiation of dilute fulvic acid solutions Soil Sci Soc Am J 41 292- 296.
Crowther, T W and 49 others (2016) Quantifying global soil carbon losses in response to warming Nature 540 104-108.
Davidson E A and Janssens I A (2006) Temperature sensitivity of soil carbon decomposition and feedbacks to climate change Nature 440 165-173.
Moran A M and Zeep G R (2000) Carbon loss and optical property changes during long term photochemical and biological degradation of estuarian dissolved organic matter Limnol Oceanogr 45 1254-1264.
Nelson D W and Sommers L E (1996) Total carbon, organic carbon, and organic matter. In: Methods of Soil Analysis, Part 3 (Sparks, D L, ed.) pp 961-1010, Soil Science Society of America, Madison, Wisc.
Saikh H, Varadachari C and Ghosh K (1998) Changes in carbon, nitrogen and phosphorus levels due to deforestation and cultivation: A case study in Simlipal National Park, India Pl Soil 198 137-145.
Varadachari C, Mitra S and Ghosh K (2017) Photochemical oxidation of soil organic matter by sunlight Proc Indian Natn Sci Acad 83 223-229.
Zeep R G, Braun A M, Hoigne J and Leenheer J A (1987) Photoproduction of hydrated electrons from natural organic solutes in aquatic environment Environ Sci Technol 21 443-450.
Published
2017-12-05
Section
Research Papers
