title: Partial shading of lateral branches affects growth, and foliage nitrogen- and water-use efficiencies in the conifer Cunninghamia lanceolata growing in a warm monsoon climate.
abstract: The degree to which branches are autonomous in their acclimation responses to alteration in light environment is still poorly understood. We investigated the effects of shading of the sapling crown of Cunninghamia lanceolata (Lamb.) Hook on the whole-tree and mid-crown branch growth and current-year foliage structure and physiology. Four treatments providing 0, 50, 75 and 90% shading compared with full daylight (denoted as Treatment(0), Treatment(50%), Treatment(75%) and Treatment(90%), and Shaded(0), Shaded(50%), Shaded(75%) and Shaded(90%) for the shaded branches and Sunlit(0), Sunlit(50%), Sunlit(75%) and Sunlit(90%) for the opposite sunlit branches under natural light conditions, respectively), were applied over two consecutive growing seasons. Shading treatments decreased the growth of basal stem diameter, leaf dry mass per unit leaf area, stomatal conductance, transpiration rate, the ratio of water-soluble to structural leaf nitrogen content, photosynthetic nitrogen-use efficiency and instantaneous and long-term (estimated from carbon isotope composition) water-use efficiency in shaded branches. Differences between shaded and sunlit branches increased with increasing severity and duration of shading. A non-autonomous, partly compensatory behavior of non-shaded branches was observed for most traits, thus reflecting the dependence between the traits of sunlit branches and the severity of shading of the opposite crown half. The results collectively indicated that tree growth and branch and leaf acclimation responses of C. lanceolata are not only affected by the local light environment, but also by relative within-crown light conditions. We argue that such a non-autonomous branch response to changes in light conditions can improve whole-tree resource optimization. These results contribute to better understanding of tree growth and utilization of water and nitrogen under heterogeneous light conditions within tree canopies.
authors.affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Tingfa
authors.initials: T
authors.lastname: Dong
authors.affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Junyu
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.
authors.forename: Yuanbin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Agricultural Sciences, PO Box 27, FI-00014, University of Helsinki, Finland.
authors.forename: Helena
authors.initials: H
authors.lastname: Korpelainen
authors.affiliation: Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51014 Tartu, Estonia.
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Niinemets
authors.affiliation: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Linan 311300, Zhejiang, China licy@zafu.edu.cn.
authors.forename: Chunyang
authors.initials: C
authors.lastname: Li
mesh_terms: D018533:Biomass; D002247:Carbon Isotopes; D002681:China; D002734:Chlorophyll / Q000378:metabolism; D002980:Climate; D032486:Cunninghamia / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D014197:Trees / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects; D014867:Water / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D014867:Water; D002734:Chlorophyll; D009584:Nitrogen
keywords: light heterogeneity; nitrogen allocation; partial shading; photosynthetic nitrogen-use efficiency