title: Distribution of three congeneric shrub species along an aridity gradient is related to seed germination and seedling emergence.
abstract: Environmental tolerance of a species has been shown to correlate positively with its geographical range. On the Ordos Plateau, three Caragana species are distributed sequentially along the precipitation gradient. We hypothesized that this geographical distribution pattern is related to environmental tolerances of the three Caragana species during seed germination and seedling emergence stages. To test this hypothesis, we examined seed germination under different temperature, light and water potentials, and monitored seedling emergence for seeds buried at eight sand depths and given different amounts of water. Seeds of C. korshinskii germinated to high percentages at 5 : 15 to 25 : 35 °C in both light and darkness, while those of C. intermedia and C. microphylla did so only at 15 : 25 and 25 : 35 °C, respectively. Nearly 30 % of the C. korshinskii seeds germinated at -1.4 MPa at 20 and 25 °C, while no seeds of the other two species did so. Under the same treatments, seedling emergence percentages of C. korshinskii were higher than those of the other two species. The rank order of tolerance to drought and sand burial of the three species is C. korshinskii > C. intermedia > C. microphylla. The amount of precipitation and sand burial depth appear to be the main selective forces responsible for the geographical distribution of these species.
authors.affiliation: Key Laboratory of Resource Plants, Beijing Botanical Garden, West China Subalpine Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China.
authors.forename: Liming
authors.initials: L
authors.lastname: Lai
authors.affiliation: Fukang Station of Desert Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, South Beijing Road, Urumqi, Xinjiang, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Key Laboratory of Resource Plants, Beijing Botanical Garden, West China Subalpine Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Resource Plants, Beijing Botanical Garden, West China Subalpine Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China.
authors.forename: Xuechun
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Resource Plants, Beijing Botanical Garden, West China Subalpine Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China.
authors.forename: Lianhe
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506, USA Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: Key Laboratory of Resource Plants, Beijing Botanical Garden, West China Subalpine Botanical Garden, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China zhengyr@ibcas.ac.cn.
authors.forename: Yuanrun
authors.initials: Y
authors.lastname: Zheng
keywords: Caragana; geographical distribution; precipitation gradient; sand burial; seed germination; seedling emergence