title: Biotic degradation at night, abiotic degradation at day: positive feedbacks on litter decomposition in drylands.
abstract: The arid and semi-arid drylands of the world are increasingly recognized for their role in the terrestrial net carbon dioxide (CO2) uptake, which depends largely on plant litter decomposition and the subsequent release of CO2back to the atmosphere. Observed decomposition rates in drylands are higher than predictions by biogeochemical models, which are traditionally based on microbial (biotic) degradation enabled by precipitation as the main mechanism of litter decomposition. Consequently, recent research in drylands has focused on abiotic mechanisms, mainly photochemical and thermal degradation, but they only partly explain litter decomposition under dry conditions, suggesting the operation of an additional mechanism. Here we show that in the absence of precipitation, absorption of dew and water vapor by litter in the field enables microbial degradation at night. By experimentally manipulating solar irradiance and nighttime air humidity, we estimated that most of the litter CO2efflux and decay occurring in the dry season was due to nighttime microbial degradation, with considerable additional contributions from photochemical and thermal degradation during the daytime. In a complementary study, at three sites across the Mediterranean Basin, litter CO2efflux was largely explained by litter moisture driving microbial degradation and ultraviolet radiation driving photodegradation. We further observed mutual enhancement of microbial activity and photodegradation at a daily scale. Identifying the interplay of decay mechanisms enhances our understanding of carbon turnover in drylands, which should improve the predictions of the long-term trend of global carbon sequestration.
authors: Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 7610001, Israel.
authors: Daniel
authors: D
authors: Gliksman
authors: Department of Biogeography and Global Change, National Museum of Natural History, Spanish Scientific Council (CSIC), C/Serrano 115bis, 28006, Madrid, Spain.
authors: Ana
authors: A
authors: Rey
authors: Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 7610001, Israel.
authors: Ron
authors: R
authors: Seligmann
authors: Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 7610001, Israel.
authors: Rita
authors: R
authors: Dumbur
authors: Department of Plant Sciences, University of California, Davis, CA, USA.
authors: Or
authors: O
authors: Sperling
authors: Ramat Hanadiv Nature Park, Zichron Yakov, Israel.
authors: Yael
authors: Y
authors: Navon
authors: Faculty of Agriculture/Landscape Management, University of Applied Sciences HTW-Dresden, Pillnitzer Platz 2, 01326, Dresden, Germany.
authors: Sabine
authors: S
authors: Haenel
authors: DIBAF (Department for Innovation in Biological, Agro-Food and Forest Systems), University of Tuscia, Via San Camillo de Lellis, 01100, Viterbo, Italy.
authors: Paolo
authors: P
authors: De Angelis
authors: Desert Research Institute, 2215 Raggio Pkwy, Reno, NV, 89512, USA.
authors: John A
authors: JA
authors: Arnone
authors: Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 7610001, Israel.
authors: José M
authors: JM
authors: Grünzweig
mesh_terms: D002245:Carbon Dioxide; D003889:Desert Climate; D017753:Ecosystem; D018515:Plant Leaves; D010944:Plants; D012987:Soil; D014466:Ultraviolet Rays
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: dew; facilitation; litter CO2 flux; litter decomposition; litter moisture-content; microbial degradation; microbial priming; photodegradation; relative humidity; semi-arid ecosystems