The role of photodegradation in surface litter decomposition across a grassland ecosystem precipitation gradient

L. A. Brandt, J. Y. King, S. E. Hobbie, D. G. Milchunas, R. L. Sinsabaugh

Research output: Contribution to journalArticlepeer-review

181 Scopus citations


Differences in litter decomposition patterns among mesic, semiarid, and arid grassland ecosystems cannot be accurately explained by variation in temperature, moisture, and litter chemistry alone. We hypothesized that ultraviolet (UV) radiation enhances decomposition in grassland ecosystems via photodegradation, more so in arid compared to mesic ecosystems, and in litter that is more recalcitrant to microbial decomposition (with high compared to low lignin concentrations). In a 2-year field study, we manipulated the amount of UV radiation reaching the litter layer at three grassland sites in Minnesota, Colorado, and New Mexico, USA, that represented mesic, semiarid, and arid grassland ecosystems, respectively. Two common grass leaf litter types of contrasting lignin: N were placed at each site under screens that either passed all solar radiation wavelengths or passed all but UV wavelengths. Decomposition was generally faster when litter was exposed to UV radiation across all three sites. In contrast to our hypothesis, the contribution of photodegradation in the decomposition process was not consistently greater at the more arid sites or for litter with higher lignin content. Additionally, at the most arid site, exposure to UV radiation could not explain decomposition rates that were faster than expected given climate constraints or lack of N immobilization by decomposing litter. Although photodegradation plays an important role in the decomposition process in a wider range of grassland sites than previously documented, it does not fully explain the differences in decomposition rates among grassland ecosystems of contrasting aridity.

Original languageEnglish (US)
Pages (from-to)765-781
Number of pages17
Issue number5
StatePublished - 2010

Bibliographical note

Funding Information:
We thank S. Graves, A. Thone, K. Crooker, Y. Sorokin, K. Hill, F. Walosin, C. Bohnet, M. Gallo, W. Eddy, C. Buyarski, and M. Stursova for their assistance in the field and lab. We thank L. Kinkel and J. McFadden for their assistance in the experimental design and for their helpful comments on the manuscript. We thank the Sevilleta National Wildlife Refuge and LTER (DEB-8811906, DEB-0080529, IBN-9411976), the USDA-ARS Central Plains Experimental Range and Shortgrass Steppe LTER (NSF DEB-0217631, 0823405), and the Cedar Creek Ecosystem Science Reserve and LTER (DEB-0080382) for use of field facilities, meteorological data, and technical support. This project was funded by NSF Ecosystem Science (DEB-0542935, DEB-0935984). Additional funding to L. Brandt was provided by an EPA STAR Fellowship, a University of Minnesota Dissertation Research Grant, the University of Minnesota Carolyn Crosby Fellowship, and the Dayton-Wilkie Natural History Funds.


  • Desert grassland
  • Extracellular enzymes
  • Lignin
  • Litter decomposition
  • Nitrogen immobilization
  • Photodegradation
  • Precipitation gradient
  • Shortgrass steppe
  • Tallgrass prairie
  • Ultraviolet (UV) radiation


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