title: UV radiation is the primary factor driving the variation in leaf phenolics across Chinese grasslands.
abstract: Due to the role leaf phenolics in defending against ultraviolet B (UVB) under previously controlled conditions, we hypothesize that ultraviolet radiation (UVR) could be a primary factor driving the variation in leaf phenolics in plants over a large geographic scale. We measured leaf total phenolics, ultraviolet-absorbing compounds (UVAC), and corresponding leaf N, P, and specific leaf area (SLA) in 151 common species. These species were from 84 sites across the Tibetan Plateau and Inner Mongolian grasslands of China with contrasting UVR (354 vs. 161 mW/cm(2) on average). Overall, leaf phenolics and UVAC were all significantly higher on the Tibetan Plateau than in the Inner Mongolian grasslands, independent of phylogenetic relationships between species. Regression analyses showed that the variation in leaf phenolics was strongly affected by climatic factors, particularly UVR, and soil attributes across all sites. Structural equation modeling (SEM) identified the primary role of UVR in determining leaf phenolic concentrations, after accounting for colinearities with altitude, climatic, and edaphic factors. In addition, phenolics correlated positively with UVAC and SLA, and negatively with leaf N and N: P. These relationships were steeper in the lower-elevation Inner Mongolian than on the Tibetan Plateau grasslands. Our data support that the variation in leaf phenolics is controlled mainly by UV radiation, implying high leaf phenolics facilitates the adaptation of plants to strong irradiation via its UV-screening and/or antioxidation functions, particularly on the Tibetan Plateau. Importantly, our results also suggest that leaf phenolics may influence on vegetation attributes and indirectly affect ecosystem processes by covarying with leaf functional traits.
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences 23 Xinning Rd, Xining, 810008, China.
authors.forename: Litong
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University Beijing, 100871, China.
authors.forename: Kechang
authors.initials: K
authors.lastname: Niu
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University Beijing, 100871, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University Beijing, 100871, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Geng
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences 23 Xinning Rd, Xining, 810008, China.
authors.forename: Zhaorong
authors.initials: Z
authors.lastname: Mi
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences 23 Xinning Rd, Xining, 810008, China ; Institute of Evolutionary Biology and Environmental Studies, University of Zurich Zürich, 8057, Switzerland.
authors.forename: Dan Fb
authors.initials: DF
authors.lastname: Flynn
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences 23 Xinning Rd, Xining, 810008, China ; Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University Beijing, 100871, China.
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: He
keywords: Inner Mongolia; Tibetan Plateau; UV radiation; leaf functional traits; leaf phenolics; ultraviolet absorbing compounds