Environmental Pollution 188 (2014) 166e171
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Effects of nitrogen additions on biomass, stoichiometry and nutrient pools of moss Rhytidium rugosum in a boreal forest in Northeast China Enzai Du a,1, Xiuyuan Liu b, Jingyun Fang a, b, * a
Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China b State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 November 2013 Received in revised form 8 February 2014 Accepted 9 February 2014
Global nitrogen (N) deposition has been enhanced with anthropogenic N emissions, and its impacts on mosses are receiving more and more attention. This study investigates how N deposition influence the biomass and stoichiometry of moss Rhytidium rugosum, using a 3-year N enrichment experiment with 0, 2, 5 and 10 g N m2 yr1 in a boreal forest in Northeast China. Low N additions caused an N redundancy and moderate to high N additions resulted in a biomass loss. N additions reduced biomass ratios of green to brown tissues and increased N and phosphorus (P) contents, suggesting changes in photosynthetic capacity and litter decomposition. Biomass N pools showed a unimodal response to the N additions, and P pools decreased under moderate and high N additions. Our findings indicate significant stoichiometric and biomass changes caused by N deposition may lead to a substantial carbon and nutrient loss in boreal moss carpets. Ó 2014 Elsevier Ltd. All rights reserved.
Keywords: Nitrogen deposition N:P ratio Carbon pool Moss Boreal forest
1. Introduction Global nitrogen (N) deposition has been enhanced with increasing anthropogenic reactive N emissions since the industrial revolution (Galloway et al., 2008), and even in remote northern regions there is an evidence of increasing N deposition (Holtgrieve et al., 2011). Mosses generally are abundant in boreal ecosystems and strongly influence the carbon (C), N and water cycling (Turetsky, 2003; Turetsky et al., 2012; Cornelissen et al., 2007). For instance, mosses have been observed to contribute substantially to above-ground net primary production in boreal forests (e.g., Harden et al., 1997; Turetsky et al., 2010). Mosses are also adept in up-taking nutrients in rainfall, retaining water, regulating soil climate and protecting soil layers (Beringer et al., 2001; Cornelissen et al., 2007). Moreover, several studies have showed that mosses hosting biological N-fixing cyanobacteria can significantly provide N inputs in boreal forest (DeLuca et al., 2002; Markham, 2009). Therefore, the threat of increasing N deposition to mosses is receiving more and more attention due to their vulnerability and
* Corresponding author. E-mail address: [email protected] (J. Fang). 1 Present address: College of Resources Science & Technology, and State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, 19 Xinjiekouwai Street, Haidian District, Beijing 100875, China. http://dx.doi.org/10.1016/j.envpol.2014.02.011 0269-7491/Ó 2014 Elsevier Ltd. All rights reserved.
critical roles (e.g. Paulissen et al., 2004; Gundale et al., 2011; Granath et al., 2012; Manninen et al., 2013). Mosses are adapted to nutrient-poor conditions and have low N content and high N use efficiency (Aldous, 2002). Under pristine conditions, growth of mosses can be readily supported by atmospheric N deposition and/or nitrogen fixation of moss-associated cyanobacteria (Berg et al., 2013). Mosses also have a high capacity of phosphorus (P) utility that they can account for 75% of the annual P accumulation in aboveground biomass in an Alaska black spruce forest (Chapin et al., 1987). Nitrogen deposition increases tissue N concentrations in some mosses (Limpens et al., 2012), while there is little information on the effects of N deposition on P content in moss tissues. Moss carpets may have high retention of nutrient pools due to their high cationic exchange and low decomposition rate (Turetsky et al., 2008; Lang et al., 2009). However, change of the nutrient pools in boreal moss carpets by N deposition is far less clear because few studies have evaluated the combining responses of the nutrient concentrations and biomass accumulation. The pleurocarpous moss (Rhytidium rugosum) is widely distributed in the Northern Hemisphere, and is always sterile and almost strongly reliant on asexual reproduction (Pfeiffer et al., 2006; Sabovljevi c and Frahm, 2011). The moss R. rugosum might be at extreme risk from disturbances such as N deposition because of its restriction in generative reproduction and long distance dispersal. In China, concerns on impacts of N deposition have
E. Du et al. / Environmental Pollution 188 (2014) 166e171
aroused due to its dramatic increase since the early 1980s (Liu et al., 2011). Mosses are highly abundant in the boreal forests in China’s Greater Khingan Mountains but little is known about their responses to the increasing N deposition. In an old-growth larch forest, an N enrichment experiment has been conducted on carpets of R. rugosum to address the following three questions: (1) do the ratio of green verse brown tissues and biomass C pool increase with elevated N deposition, (2) does N content increase and P content decrease in moss tissues with enhanced N deposition, and (3) will the N and P pools be accumulated with increasing N deposition?
2. Material and methods 2.1. Site description The site of this study is located at the National Field Research Station of Daxing’anling Forest Ecosystem (50 560 N, 121300 E) in Greater Khingan Mountains, Northeast China. The annual mean temperature and annual mean precipitation are 5.4 C and 450e550 mm, respectively. This study has been conducted in a pristine old-growth larch forest (>300 years) with a vertical structure of three layers: (1) tree layer (>3 m), with Larix gmelinii as the dominant species; (2) shrub layer (0.3e3 m), with a species composition of Betula fruticosa, Ledum palustre, Rhododendron dahuricum and Vaccinium uliginosum; and (3) the floor layer (
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Effects of nitrogen additions on biomass, stoichiometry and nutrient pools of moss Rhytidium rugosum in a boreal forest in Northeast China Enzai Du a,1, Xiuyuan Liu b, Jingyun Fang a, b, * a
Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China b State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 November 2013 Received in revised form 8 February 2014 Accepted 9 February 2014
Global nitrogen (N) deposition has been enhanced with anthropogenic N emissions, and its impacts on mosses are receiving more and more attention. This study investigates how N deposition influence the biomass and stoichiometry of moss Rhytidium rugosum, using a 3-year N enrichment experiment with 0, 2, 5 and 10 g N m2 yr1 in a boreal forest in Northeast China. Low N additions caused an N redundancy and moderate to high N additions resulted in a biomass loss. N additions reduced biomass ratios of green to brown tissues and increased N and phosphorus (P) contents, suggesting changes in photosynthetic capacity and litter decomposition. Biomass N pools showed a unimodal response to the N additions, and P pools decreased under moderate and high N additions. Our findings indicate significant stoichiometric and biomass changes caused by N deposition may lead to a substantial carbon and nutrient loss in boreal moss carpets. Ó 2014 Elsevier Ltd. All rights reserved.
Keywords: Nitrogen deposition N:P ratio Carbon pool Moss Boreal forest
1. Introduction Global nitrogen (N) deposition has been enhanced with increasing anthropogenic reactive N emissions since the industrial revolution (Galloway et al., 2008), and even in remote northern regions there is an evidence of increasing N deposition (Holtgrieve et al., 2011). Mosses generally are abundant in boreal ecosystems and strongly influence the carbon (C), N and water cycling (Turetsky, 2003; Turetsky et al., 2012; Cornelissen et al., 2007). For instance, mosses have been observed to contribute substantially to above-ground net primary production in boreal forests (e.g., Harden et al., 1997; Turetsky et al., 2010). Mosses are also adept in up-taking nutrients in rainfall, retaining water, regulating soil climate and protecting soil layers (Beringer et al., 2001; Cornelissen et al., 2007). Moreover, several studies have showed that mosses hosting biological N-fixing cyanobacteria can significantly provide N inputs in boreal forest (DeLuca et al., 2002; Markham, 2009). Therefore, the threat of increasing N deposition to mosses is receiving more and more attention due to their vulnerability and
* Corresponding author. E-mail address: [email protected] (J. Fang). 1 Present address: College of Resources Science & Technology, and State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, 19 Xinjiekouwai Street, Haidian District, Beijing 100875, China. http://dx.doi.org/10.1016/j.envpol.2014.02.011 0269-7491/Ó 2014 Elsevier Ltd. All rights reserved.
critical roles (e.g. Paulissen et al., 2004; Gundale et al., 2011; Granath et al., 2012; Manninen et al., 2013). Mosses are adapted to nutrient-poor conditions and have low N content and high N use efficiency (Aldous, 2002). Under pristine conditions, growth of mosses can be readily supported by atmospheric N deposition and/or nitrogen fixation of moss-associated cyanobacteria (Berg et al., 2013). Mosses also have a high capacity of phosphorus (P) utility that they can account for 75% of the annual P accumulation in aboveground biomass in an Alaska black spruce forest (Chapin et al., 1987). Nitrogen deposition increases tissue N concentrations in some mosses (Limpens et al., 2012), while there is little information on the effects of N deposition on P content in moss tissues. Moss carpets may have high retention of nutrient pools due to their high cationic exchange and low decomposition rate (Turetsky et al., 2008; Lang et al., 2009). However, change of the nutrient pools in boreal moss carpets by N deposition is far less clear because few studies have evaluated the combining responses of the nutrient concentrations and biomass accumulation. The pleurocarpous moss (Rhytidium rugosum) is widely distributed in the Northern Hemisphere, and is always sterile and almost strongly reliant on asexual reproduction (Pfeiffer et al., 2006; Sabovljevi c and Frahm, 2011). The moss R. rugosum might be at extreme risk from disturbances such as N deposition because of its restriction in generative reproduction and long distance dispersal. In China, concerns on impacts of N deposition have
E. Du et al. / Environmental Pollution 188 (2014) 166e171
aroused due to its dramatic increase since the early 1980s (Liu et al., 2011). Mosses are highly abundant in the boreal forests in China’s Greater Khingan Mountains but little is known about their responses to the increasing N deposition. In an old-growth larch forest, an N enrichment experiment has been conducted on carpets of R. rugosum to address the following three questions: (1) do the ratio of green verse brown tissues and biomass C pool increase with elevated N deposition, (2) does N content increase and P content decrease in moss tissues with enhanced N deposition, and (3) will the N and P pools be accumulated with increasing N deposition?
2. Material and methods 2.1. Site description The site of this study is located at the National Field Research Station of Daxing’anling Forest Ecosystem (50 560 N, 121300 E) in Greater Khingan Mountains, Northeast China. The annual mean temperature and annual mean precipitation are 5.4 C and 450e550 mm, respectively. This study has been conducted in a pristine old-growth larch forest (>300 years) with a vertical structure of three layers: (1) tree layer (>3 m), with Larix gmelinii as the dominant species; (2) shrub layer (0.3e3 m), with a species composition of Betula fruticosa, Ledum palustre, Rhododendron dahuricum and Vaccinium uliginosum; and (3) the floor layer (
