Early exposure to UV radiation overshadowed by precipitation and litter quality as drivers of decomposition in the northern Chihuahuan Desert

• Published in: PloS one Vol. 14; no. 2; p. e0210470
• Main Authors: Hewins, Daniel B, Lee, Hanna, Barnes, Paul W, McDowell, Nathan G, Pockman, William T, Rahn, Thom, Throop, Heather L
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.02.2019; Public Library of Science (PLoS)
• Subjects: Arid regions; Biogeochemical cycles; Biogeochemistry; Biology; Cellulose; Cellulose - metabolism; Climate; Climate change; Decay; Decay rate; Decomposition; Desert Climate; Deserts; Drought; Droughts; drylands; Earth Sciences; Ecology; Ecology and Environmental Sciences; Ecosystem; Ecosystem biology; Ecosystems; Environmental changes; ENVIRONMENTAL SCIENCES; Exposure; Filter paper; Hot climates; Laboratories; Leaf litter; Lignin; Lignin - metabolism; litter decomposition; Mesquite; Microorganisms; Motor vehicle drivers; New Mexico; Nitrogen; Nitrogen - metabolism; Organic chemistry; Photodegradation; Physical Sciences; Plant growth; Plant Leaves - physiology; Plant Leaves - radiation effects; Plant Physiological Phenomena - radiation effects; Plants - radiation effects; Polysaccharides; Precipitation; Precipitation (Meteorology); precipitation manipulation; Primary production; Prosopis; Prosopis - physiology; Prosopis - radiation effects; Radiation effects; Radiation exposure; Radiation measurement; Radiotherapy; Rainfall; rainout shelter; Solar radiation; Studies; Substrates; Terrestrial environments; Tilia - physiology; Tilia - radiation effects; Ultraviolet radiation; Ultraviolet Rays; New Mexico; Rhode Island; Chihuahuan Desert; United States > US; Arizona
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0210470

Dryland ecosystems cover nearly 45% of the Earth's land area and account for large proportions of terrestrial net primary production and carbon pools. However, predicting rates of plant litter decomposition in these vast ecosystems has proven challenging due to their distinctly dry and often hot climate regimes, and potentially unique physical drivers of decomposition. In this study, we elucidated the role of photopriming, i.e. exposure of standing dead leaf litter to solar radiation prior to litter drop that would chemically change litter and enhance biotic decay of fallen litter. We exposed litter substrates to three different UV radiation treatments simulating three-months of UV radiation exposure in southern New Mexico: no light, UVA+UVB+Visible, and UVA+Visible. There were three litter types: mesquite leaflets (Prosopis glandulosa, litter with high nitrogen (N) concentration), filter paper (pure cellulose), and basswood (Tilia spp, high lignin concentration). We deployed the photoprimed litter in the field within a large scale precipitation manipulation experiment: ∼50% precipitation reduction, ∼150% precipitation addition, and ambient control. Our results revealed the importance of litter substrate, particularly N content, for overall decomposition in drylands, as neither filter paper nor basswood exhibited measurable mass loss over the course of the year-long study, while high N-containing mesquite litter exhibited potential mass loss. We saw no effect of photopriming on subsequent microbial decay. We did observe a precipitation effect on mesquite where the rate of decay was more rapid in ambient and precipitation addition treatments than in the drought treatment. Overall, we found that precipitation and N played a critical role in litter mass loss. In contrast, photopriming had no detected effects on mass loss over the course of our year-long study. These results underpin the importance of biotic-driven decomposition, even in the presence of photopriming, for understanding litter decomposition and biogeochemical cycles in drylands.