title: Sensitivity of the xerophytic moss Syntrichia caninervis to prolonged simulated nitrogen deposition.
abstract: Biological soil crusts, comprising assemblages of cyanobacteria, fungi, lichens and mosses, are common in dryland areas and are important elements in these ecosystems. Increasing N deposition has led to great changes in community structure and function in desert ecosystems worldwide. However, it is unclear how moss crusts respond to increased atmospheric N deposition, especially in terms of growth and physiological parameters. The aim of this study was to understand how Syntrichia caninervis, a dominant species in moss crusts in many northern hemisphere desert ecosystems, responds to added N.
  
  
  
  The population and shoot growth, and physiological responses of S. caninervis to six different doses of simulated N deposition (0, 0·3, 0·5, 1·0, 1·5 and 3·0 g N m(-2) year(-1)) were studied over a 3 year period.
  
  
  
  Low amounts of added N increased shoot length and leaf size, whereas high doses reduced almost all growth parameters. Moss shoot density increased, but population biomass decreased with high N. Low N augmented chlorophyll b, total chlorophyll content and soluble protein concentrations, but not chlorophyll a or chlorophyll fluorescence. High N was detrimental to all these indices. Soluble sugar concentration declined with increased N, but proline concentration was not affected significantly. Antioxidant enzyme activities generally decreased with low N additions and increased with high doses of simulated N deposition.
  
  
  
  Low amounts of added N (0-0·5 g N m(-2) year(-1)) may enhance moss growth and vitality, while higher amounts have detrimental effects.
authors.affiliation: Xinjiang Institute of Ecology and Geography, Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China zhangym@ms.xjb.ac.cn.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Xinjiang Institute of Ecology and Geography, Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Xinjiang Institute of Ecology and Geography, Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China State Key Laboratory of Earth Surface Processes and Resource Ecology, College of life sciences of Beijing Normal University, Beijing 100875, China.
authors.forename: Benfeng
authors.initials: B
authors.lastname: Yin
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
authors.forename: Alison
authors.initials: A
authors.lastname: Downing
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D019068:Bryopsida / Q000502:physiology*; D002681:China; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D003889:Desert Climate; D017753:Ecosystem; D004785:Environmental Pollutants / Q000378:metabolism; D004798:Enzymes / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D012987:Soil / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D004785:Environmental Pollutants; D004798:Enzymes; D012987:Soil; D002734:Chlorophyll; C037184:chlorophyll b; D011392:Proline; D009584:Nitrogen; D000077194:Chlorophyll A
keywords: Antioxidant enzyme; Syntrichia caninervis; chlorophyll; fluorescence; nitrogen deposition; osmotic substance