Effects of Different Vegetation Zones on CH4 and N2O Emissions in Coastal Wetlands: A Model Case Study

Liu, Yuhong; Wang, Lixin; Bao, Shumei; Liu, Huamin; Yu, Junbao; Wang, Yu; Shao, Hongbo; Ouyang, Yan; An, Shuqing

doi:https://doi.org/10.1155/2014/412183

The Scientific World Journal

On this page

Abstract Introduction Materials and Methods Results Conclusions Acknowledgments References Copyright Related Articles

Special Issue

Plant Abio-Stress and Bioresources Utilization for Sustainable Development

View this Special Issue

Research Article | Open Access

Volume 2014 | Article ID 412183 | https://doi.org/10.1155/2014/412183

Effects of Different Vegetation Zones on CH₄ and N₂O Emissions in Coastal Wetlands: A Model Case Study

Yuhong Liu,^1,2Lixin Wang,¹Shumei Bao,¹Huamin Liu,³Junbao Yu,²Yu Wang,⁴Hongbo Shao,^1,2Yan Ouyang,⁴and Shuqing An⁴

Academic Editor: Xu Gang

Received08 Mar 2014

Accepted21 Mar 2014

Published29 Apr 2014

Abstract

The coastal wetland ecosystems are important in the global carbon and nitrogen cycle and global climate change. For higher fragility of coastal wetlands induced by human activities, the roles of coastal wetland ecosystems in CH₄ and N₂O emissions are becoming more important. This study used a DNDC model to simulate current and future CH₄ and N₂O emissions of coastal wetlands in four sites along the latitude in China. The simulation results showed that different vegetation zones, including bare beach, Spartina beach, and Phragmites beach, produced different emissions of CH₄ and N₂O in the same latitude region. Correlation analysis indicated that vegetation types, water level, temperature, and soil organic carbon content are the main factors affecting emissions of CH₄ and N₂O in coastal wetlands.

1. Introduction

Methane (CH₄) and nitrous oxide (N₂O) are important active greenhouse gases contributing to global warming [1, 2]. Contributions of CH₄ and N₂O to global warming are 21 and 310 times of CO₂ [3] and occupy about 15% and 5% of greenhouse effects [4], respectively. Moreover, the two kinds of gases in the atmosphere are growing at 3% and 0.22% per year, respectively [5]. As an important source and sink of greenhouse gases, the coastal wetland ecosystems are important in the global carbon and nitrogen cycle and global climate change. Since coastal wetlands belong to the ecologically fragile zone [6], it is important to understand the relationships between vegetation characteristics and CH₄ and N₂O emissions.

Many studies on CH₄ and N₂O emissions in natural wetlands are carried out since the 1990s and focus on their emissions, absorptions, spatial and temporal variations, and environmental factors. Although the effects of vegetation features on CH₄ and N₂O emissions from wetland ecosystems worldwide have been investigated (e.g., [7–9]), these studies in our country are still relatively weak. In China, greenhouse gas emission flux and the effects of environmental factors are mainly concentrated on Phragmites wetland of the Sanjiang plain [10] and in the southern mangrove coastal wetlands [11, 12]. Recently, the spatial and temporal variations of N₂O and CH₄ fluxes associated with abiotic sediment parameters are quantified in the coastal marsh dominated by Suaeda salsa in the Yellow River estuary [13], and the effects of different vegetation, Spartina alterniflora and Phragmites australis, on CH₄ and N₂O emissions are investigated by using experimental mesocosms [9]. However, these studies do not compare roles of vegetation zone in different areas in CH₄ and N₂O emissions and future variations of CH₄ and N₂O emissions in coastal wetlands of China.

In this study, denitrification-decomposition (DNDC) model was used to simulate wetland biogeochemistry processes and its response to global warming in the four sites of coastal zone distributing along the latitude. By simulation analysis, the following research questions were focused on the following.(1)Are there differences in effects of different vegetation zones on CH₄ and N₂O emissions of coastal wetlands in different sites along latitude?(2)How will CH₄ and N₂O emissions change with increasing temperature in coastal wetlands?

2. Materials and Methods

2.1. Study Areas

Four coastal wetlands were chosen in Sheyang, Dongtai, and Nantong of Jiangsu province and Chongming of Shanghai city (Figure 1). Each coastal wetland was divided into the bare beach, Spartina beach, and Phragmites beach according to vegetation type distribution.

Coastal zone of Jiangsu is affected by marine and continental climate. Average annual temperature is about 15°C. Average annual rainfall increases gradually from north to south, and average annual relative humidity decreases from south to north.

Chongming in Shanghai city is affected by subtropical marine monsoon climate. Average annual temperature is about 16°C, and average annual rainfall is about 1,030 mm.

2.2. Description of DNDC Model

The DNDC model takes denitrification and decomposition as the main processes applied in soil carbon and nitrogen biogeochemical cycles [14]. DNDC model has been applied in agriculture, forest, and grassland research worldwide for calculating soil carbon sequestration and greenhouse gas emissions [15]. This model consists of six submodels including soil, climate, plant growth, decomposition of organic matter, nitrification, denitrification, and fermentation process. Input variables of this model are soil properties, climate conditions, and agricultural production measures, and output variables are daily C and N content in soil and plant, soil temperature, and humidity data at different levels, and output variables are the emissions flux of CO₂, CH₄, N₂O, and NO.

2.3. Acquisition of Meteorological Data

Daily observation meteorological data in 1988 (for 80s) and 2004 (for 00s) are obtained from “China Meteorological Data Sharing Service System” (http://cdc.cma.gov.cn/). According to input data requirements, the daily maximum temperature (°C), the daily minimum temperature (°C), the rainfall data (cm), and other correlated data are turned into text format (ASCII encoding) and ready for input into the model. Future meteorological data are calculated by IPCC simulations.

2.4. Collection of Soil Parameters

Land use type and soil texture in this study are wetlands and silt loam, respectively, which were set directly in the options of DNDC model. Soil bulk density, soil pH, and surface soil organic carbon (SOC) content are obtained from literatures and field measurements measured in 2004. By inputting these soil data, the model would give other corresponding soil data, and default data would be used in this study.

2.5. Collection of Plant Physiological Parameters

In this paper, plant types included no plant (bare beach), Spartina, and Phragmites, which were not listed in the DNDC model. Therefore, we chose “0 Fallow” of the DNDC model to simulate a bare beach, while Spartina and Phragmites were created as new plant options. The two plant physiological parameters including biomass, , LAI, and water requirement, for this model, were collected by literatures and field measurements in 2004.

2.6. Hydrological Data Preparation

The DNDC model provides four patterns to simulate the influence of flooding, including irrigation, rain-fed, observed water-table data, and empirical parameters. This study adopted observed water-table data pattern. Tidal data were obtained from tidal tables of the Yellow Sea and Bohai Sea, in 2004 and 1990, and Xiaoyang, Lvsi, Sheshan, and Sheyang port were chosen as tidal stations for Dongtai, Nantong, Chongming, and Sheyang, respectively. Every 10-day tidal height and tidal height datum of the port and the elevation of different wetlands were used to calculate the water levels of bare beach, Spartina beach, and Phragmites beach, which were made into water level table finally.

3. Results

3.1. Comparison of CH₄ and N₂O Annual Emission Flux of Different Beaches

The annual CH₄ emission flux of different beaches including Sheyang, Dongtai, Nantong, and Chongming has a similar trend between 80s and 00s (Figure 2), and similar phenomenon occurred for N₂O emission flux (Figure 3). The order of CH₄ emission ability in different beaches is Spartina beach > Phragmites beach > bare flat, while for N₂O the order is Phragmites beach > Spartina beach > bare flat (Figures 2 and 3). Spartina alterniflora and Phragmites australis increase CH₄ and N₂O emission fluxes contrasting with bare beach, which suggests that the vegetation type is one of the important factors affecting warm gas emission. CH₄ emission ability of Spartina beach is higher than Phragmites beach, while N₂O emission ability is contrary.

3.2. Comparison of Future CH₄ and N₂O Annual Emission Flux

Based on Figures 4 and 5, CH₄ and N₂O emission flux of three different coastal wetlands increase with increasing time from the present situation to 2100 in four study sites, which is consistent with the predicted trend of rising temperature (Figure 6). For different beaches, CH₄ emission flux of Spartina beach (MC) is > Phragmites beach (LW) > bare flat (GT), and N₂O emission flux of Phragmites beach is > Spartina beach > bare beach.

In different sites, CH₄ emission flux of CM and SY in MC and GT beach is higher than DT and NT, while on LW beach this trend is contrary. For N₂O emission flux, NT is the highest while SY is the lowest.

3.3. Roles of Different Factors in CH₄ and N₂O Emissions

By correlation analysis, CH₄ and N₂O emission flux are significantly correlated with soil organic carbon content (, , resp.) and with maximum biomass of per unit area (, ; , ). Soil pH has a significant correlation with CH₄ emission flux (, ) and N₂O emission flux (, ). CH₄ and N₂O emission flux have significant negative correlation with average water level (, ; , ).

Study results show that CH₄ emission flux in coastal wetland has significant correlation with temperature (, ) and also is affected significantly by rainfall (, ). N₂O emission flux is positively correlated with temperature (, ); however, N₂O flux and total annual precipitation have no relevance.

4. Discussions

4.1. Roles of Similar Vegetation Distribution Zone in CH₄ and N₂O Emissions in Coastal Wetland along Latitude

Some studies showed that the emission of trace gases from wetlands was controlled by multiple factors like soil temperature, hydrology, and vegetation (e.g., [16–20]). Our study also indicated that vegetation, soil characteristics, and climate conditions affected emissions of CH₄ and N₂O in coastal wetlands. Moreover, it was noticeable that, at different sites along latitude, similar CH₄ and N₂O emission patterns were found, which was caused by similar vegetation distribution zone including bare beach, Spartina beach, and Phragmites beach in coastal wetlands. This indicated that vegetation was an important factor affecting greenhouse gas emission [21]. Van der Nat and Middelburg [22] found that gas emissions were affected collectively by vegetation type and species composition in tidal marshes, and increasing CH₄ flux was achieved by improvement of organic substrates and transportation of plant aerenchyma reducing oxidation of methane [23, 24]. Windham and Ehrenfeld [25] pointed out that, in two different tidal areas dominated by reeds and cattails, CH₄ emissions had some obvious differences. Exotic-species invasions affecting the vegetation structure of wetland ecosystems [25] would change the input of organic matter to soil [26]. Cheng et al. [9] reported that CH₄ emissions were significantly correlated with plant biomass and stem density for Spartina and Phragmites, while N₂O emissions were not accorded with this trend. Our model study also showed that, in a vegetation gradient zone, the effects of exotic-species Spartina on CH₄ emissions were more than native species Phragmites for its higher biomass and organic matter. However, this phenomenon did not exist in N₂O emission [27]. This was attributed to different mechanisms of CH₄ and N₂O emissions. Therefore, different vegetation distribution in coastal wetland was actually an important factor during the processes of CH₄ and N₂O emissions.

4.2. Effects of Temperature on CH₄ and N₂O Emissions

The changes between present and future CH₄ and N₂O emission flux in the same site were mainly due to future temperature higher than present temperature. Temperature, especially soil temperature, played a very important role in CH₄ production and emission. Soil temperature directly affected the quantity, structure, and activity of a series of microflora that were involved in the process of the methane production and oxidation [7] and methane transport in soil [28]. Huttunen et al. [29] found that the correlation between CH₄ emission flux and peat surface temperature was most significant in all factors in the northern peatland, and incubation experiments also proved this relationship [30]. Our study results also showed that CH₄ emission flux in coastal wetland had significant correlation with temperature.

Hotness, humidity, and high carbon and nitrogen content of the soil were the best environment for N₂O production. The temperature was an important environmental factor in soil N₂O production and emission, but its relationship with N₂O emission was still controversial. Luo et al. [31] argued that temperature affected soil nitrification and denitrification, and Dorland and Beauchamp [32] found that, while temperature varied from −2°C to 25°C, the amount of the square root of the denitrification had a linear relationship with temperature. However, some studies also suggested that the temperature impact was not obvious. This study was consistent with the result of [33] that N₂O flux was positively correlated with temperature.

Comparisons of CH₄ and N₂O flux in different locations were complex. Multiple factors could cause the regional difference, such as temperature, rainfall, water level, and soil pH (e.g., [34, 35]).

5. Conclusions

By simulating CH₄ and N₂O emissions in the coastal wetlands by DNDC model, CH₄ emission ability of Spartina beach in three different vegetation zones was the highest, while the highest N₂O emission ability existed in Phragmites beach. This trend was very similar in the different sites including Sheyang, Dongtai, Nantong, and Chongming. By correlation analysis, CH₄ and N₂O emission fluxes were positively correlated with soil organic carbon content, temperature, and maximum biomass of per unit area and were negatively correlated with average water level. Comparisons of CH₄ and N₂O flux in different locations were complex, which were caused by multiple factors, such as temperature, rainfall, water level, and soil pH.

Conflict of Interests

The authors declare that they have no conflict of interests regarding the publication of this paper.

Authors’ Contribution

Yuhong Liu and Lixin Wang contributed to this work equally.

Acknowledgments

This study was supported by the National Key Basic Research Program of China (no. 2014CB138802), National Key Technology R&D Program of China (nos. 2011BAC02B03 and 2013BAC09B03), the National Natural Science Funds of China (no. 31060076, 41261009), and the National Basic Research Program of China (no. 2013CB430405).

References

IPCC, Climate Change: The Scientific Basis, Cambridge University Press, New York, NY, USA, 2001.
D. Song, M. R. Su, J. Yang, and B. Chen, “Greenhouse gas emission accounting and management of low-carbon community,” The Scientific World Journal, vol. 2012, Article ID 613721, 6 pages, 2012.
View at: Publisher Site | Google Scholar
IPCC, Climate Change: The Physical Science Basis, Cambridge University Press, Cambridge, UK, 2007.
J. E. Hansen and A. A. Lacis, “Sun and dust versus greenhouse gases: an assessment of their relative roles in global climate change,” Nature, vol. 346, no. 6286, pp. 713–719, 1990.
View at: Publisher Site | Google Scholar
S. Ghosh, D. Majumdar, and M. C. Jain, “Methane and nitrous oxide emissions from an irrigated rice of North India,” Chemosphere, vol. 51, no. 3, pp. 181–195, 2003.
View at: Publisher Site | Google Scholar
X. L. Zhang, P. Y. Li, P. Li, and X. Y. Xu, “Present conditions and prospects of study on coastal wetlands in China,” Advances in Marine Science, vol. 23, no. 1, pp. 83–91, 2005 (Chinese).
View at: Google Scholar
J. P. Schimel and J. Gulledge, “Microbial community structure and global trace gases,” Global Change Biology, vol. 4, no. 7, pp. 745–758, 1998.
View at: Publisher Site | Google Scholar
L. Kutzbach, D. Wagner, and E.-M. Pfeiffer, “Effect of microrelief and vegetation on methane emission from wet polygonal tundra, Lena Delta, Northern Siberia,” Biogeochemistry, vol. 69, no. 3, pp. 341–362, 2004.
View at: Publisher Site | Google Scholar
X. L. Cheng, R. H. Peng, J. Q. Chen et al., “CH₄ and N₂O emissions from Spartina alterniflora and Phragmites australis in experimental mesocosms,” Chemosphere, vol. 68, no. 3, pp. 420–427, 2007.
View at: Publisher Site | Google Scholar
G. H. Huang, Y. X. Li, G. X. Chen, Y. C. Yang, and C. W. Zhao, “Influence of environmental factors on CH₄ emission from Reed Wetland,” Chinese Journal of Environmental Science, vol. 22, no. 1, pp. 1–5, 2001.
View at: Google Scholar
M. A. K. Khalil, R. A. Rasmussen, M.-X. Wang, and L. Ren, “Emissions of trace gases from Chinese rice fields and biogas generators: CH₄, N₂O, CO, CO₂ chlorocarbons, and hydrocarbons,” Chemosphere, vol. 20, no. 1-2, pp. 207–226, 1990.
View at: Publisher Site | Google Scholar
Y. Ye, C. Y. Lu, P. Lin, F. Y. Tan, and Y. S. Huang, “Diurnal change of CH₄ fluxes from esturine mangrove wetlands,” Acta Oceanologica Sinica, vol. 22, no. 3, pp. 103–109, 2000 (Chinese).
View at: Google Scholar
Z. G. Sun, L. L. Wang, H. Q. Tian, H. H. Jiang, X. J. Mou, and W. L. Sun, “Fluxes of nitrous oxide and methane in different coastal Suaeda salsa marshes of the Yellow River estuary, China,” Chemosphere, vol. 90, no. 2, pp. 856–865, 2013.
View at: Publisher Site | Google Scholar
C. Li, S. Frolking, and T. A. Frolking, “A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity,” Journal of Geophysical Research: Atmospheres, vol. 97, no. 9, pp. 9759–9776, 1992.
View at: Google Scholar
C. S. Li, “Modeling terrestrial ecosystems, complex systems and complexity,” Science, vol. 1, no. 1, pp. 49–57, 2004 (Chinese).
View at: Google Scholar
H. Kang, C. Freeman, and M. A. Lock, “Trace gas emissions from a north Wales fen—role of hydrochemistry and soil enzyme activity,” Water, Air, and Soil Pollution, vol. 105, no. 1-2, pp. 107–116, 1998.
View at: Publisher Site | Google Scholar
H. Rusch and H. Rennenberg, “Black alder (Alnus glutinosa (L.) Gaertn.) trees mediate methane and nitrous oxide emission from the soil to the atmosphere,” Plant and Soil, vol. 201, no. 1, pp. 1–7, 1998.
View at: Publisher Site | Google Scholar
Y. Ye, C. Y. Lu, and P. Lin, “Methane production, oxidation, transportation rate and pool in sediments of an Avicennia marina mangrove at Dongyu, Xiamen,” Journal of Oceanography in Taiwan Strait, vol. 20, no. 2, pp. 236–244, 2001 (Chinese).
View at: Google Scholar
N. Fenner, D. J. Dowrick, M. A. Lock, C. R. Rafarel, and C. Freeman, “A novel approach to studying the effects of temperature on soil biogeochemistry using a thermal gradient bar,” Soil Use and Management, vol. 22, no. 3, pp. 267–273, 2006.
View at: Publisher Site | Google Scholar
J. L. Morse, M. Ardón, and E. S. Bernhardt, “Greenhouse gas fluxes in southeastern US coastal plain wetlands under contrasting land uses,” Ecological Applications, vol. 22, no. 1, pp. 264–280, 2012.
View at: Publisher Site | Google Scholar
M. Hirota, Y. Senga, Y. Seike, S. Nohara, and H. Kunii, “Fluxes of carbon dioxide, methane and nitrous oxide in two contrastive fringing zones of coastal lagoon, Lake Nakaumi, Japan,” Chemosphere, vol. 68, no. 3, pp. 597–603, 2007.
View at: Publisher Site | Google Scholar
F.-J. van der Nat and J. J. Middelburg, “Methane emission from tidal freshwater marshes,” Biogeochemistry, vol. 49, no. 2, pp. 103–121, 2000.
View at: Publisher Site | Google Scholar
M. Roura-Carol and C. Freeman, “Methane release from peat soils: effects of Sphagnum and Juncus,” Soil Biology and Biochemistry, vol. 31, no. 2, pp. 323–325, 1999.
View at: Publisher Site | Google Scholar
H. Brix, B. K. Sorrell, and P. T. Orr, “Internal pressurisation and convective gas flow in some emergent freshwater macrophytes,” Limnology and Oceanography, vol. 37, no. 7, pp. 1420–1433, 1992.
View at: Publisher Site | Google Scholar
L. Windham and J. G. Ehrenfeld, “Net impact of a plant invasion on nitrogen-cycling processes within a brackish tidal marsh,” Ecological Applications, vol. 13, no. 4, pp. 883–896, 2003.
View at: Google Scholar
J. G. Ehrenfeld, P. Kourtev, and W. Huang, “Changes in soil functions following invasions of exotic understory plants in deciduous forests,” Ecological Applications, vol. 11, no. 5, pp. 1287–1300, 2001.
View at: Google Scholar
L. H. Zhang, L. P. Song, L. W. Zhang, H. B. Shao, X. B. Chen, and K. Yan, “Seasonal dynamics in nitrous oxide emissions under different types of vegetation in saline-alkaline soils of the Yellow River Delta, China and implications foreco-restoring coastal wetland,” Ecological Engineer, vol. 61, pp. 82–89, 2013.
View at: Publisher Site | Google Scholar
W. X. Ding, Z. C. Cai, and D. X. Wang, “Preliminary budget of methane emissions from natural wetlands in China,” Atmospheric Environment, vol. 38, no. 5, pp. 751–759, 2004.
View at: Publisher Site | Google Scholar
J. T. Huttunen, H. Nykänen, J. Turunen, and P. J. Martikainen, “Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscandia,” Atmospheric Environment, vol. 37, no. 1, pp. 147–151, 2003.
View at: Publisher Site | Google Scholar
J. A. MacDonald, D. Fowler, K. J. Hargreaves, U. Skiba, I. D. Leith, and M. B. Murray, “Methane emission rates from a northern wetland: response to temperature, water table and transport,” Atmospheric Environment, vol. 32, no. 19, pp. 3219–3227, 1998.
View at: Publisher Site | Google Scholar
J. Luo, R. W. Tillman, and P. R. Ball, “Factors regulating denitrification in a soil under pasture,” Soil Biology and Biochemistry, vol. 31, no. 6, pp. 913–927, 1999.
View at: Publisher Site | Google Scholar
S. Dorland and E. G. Beauchamp, “Denitrification and ammonification at low soil temperatures,” Canadian Journal of Soil Science, vol. 71, no. 3, pp. 293–303, 1991.
View at: Google Scholar
W. B. Xv, W. P. Liu, and G. S. Liu, “Effect of temperature on N₂O emissions from sub-tropical upland soils,” Acta Pedologica Sinica, vol. 8, no. 1, pp. 1–8, 2002.
View at: Google Scholar
Z. Q. Luan, Z. X. Wang, D. D. Yan, G. H. Liu, and Y. Y. Xu, “The ecological response of Carex lasiocarpa community in the riparian wetlands to the environmental gradient of water depth in Sanjiang Plain, Northeast China,” The Scientific World Journal, vol. 2013, Article ID 402067, 7 pages, 2013.
View at: Publisher Site | Google Scholar
Z. Dai, C. C. Trettin, C. Li, H. Li, G. Sun, and D. M. Amatya, “Effect of assessment scale on spatial and temporal variations in CH₄, CO₂, and N₂O fluxes in a forested Wetland,” Water, Air, and Soil Pollution, vol. 223, no. 1, pp. 253–265, 2012.
View at: Publisher Site | Google Scholar

Copyright

Copyright © 2014 Yuhong Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

1710

Downloads

1149

Citations