Responses of soil microbial biomass and bacterial community structure to closed-off management (an ecological natural restoration measures): A case study of Dongting Lake wetland, middle China
- 1 College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China
- 2 Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
- 3 Changjiang River Scientific Research Institute, Wuhan 430072, PR China
- 4 State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan 430072, PR China
- 5 Key Laboratory of Reservoir Aquatic Environment of CAS, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China
- Received 19 November 2015, Accepted 2 March 2016, Available online 29 March 2016
Highlights
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Closed-off management applied to restore and protect many important wetlands.
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We compared soil microbial indicators in management area (MA) and contrast area (CA).
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Soil microbial biomass and diversity had significant increases after management.
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Functional marker genes of nitrogen cycling also had significant changes.
Soil microbial biomass (SMB) and bacterial community structure, which are critical to global ecosystem and fundamental ecological processes, are sensitive to anthropogenic activities and environmental conditions. In this study, we examined the possible effects of closed-off management (an ecological natural restoration measures, ban on anthropogenic activity, widely employed for many important wetlands) on SMB, soil bacterial community structure and functional marker genes of nitrogen cycling in Dongting Lake wetland. Soil samples were collected from management area (MA) and contrast area (CA: human activities, such as hunting, fishing and draining, are permitted) in November 2013 and April 2014. Soil properties, microbial biomass carbon (MBC), and bacterial community structure were investigated. Comparison of the values of MA and CA showed that SMB and bacterial community diversity of the MA had a significant increase after 7 years closed-off management. The mean value of Shannon–Weiner diversity index of MA and CA respectively were 2.85 and 2.07. The gene copy numbers of 16S rRNA and nosZ of MA were significant higher than those of CA. the gene copy numbers of ammonia-oxidizing archaea (AOA) and nirK of MA were significant lower than those of CA. However, there was no significant change in the gene copy numbers of ammonia-oxidizing bacteria (AOB) and nirS.
Key words
- Microbial biomass carbon;
- Bacterial community diversity;
- Nitrogen;
- Ecological management;
- Ecological restoration;
- Wetland
Wetlands provide habitats for biota on the earth and play a key role in biodiversity protection (1). As a large carbon pools, they are also critical to global carbon cycles (2). Therefore, wetlands are important for global ecology and climate change. The ecological restoration of degraded wetland captured the increasing attention around the world. Soil microorganism is critical to global ecosystem, plays a critical role in regulating the global nutrients and carbon cycling and performs fundamental ecological processes like mineralization and decomposition 1, 3 and 4. Soil microbial biomass (SMB) and soil bacterial community structure are sensitive to anthropogenic activities 5 and 6 and local environmental conditions 1 and 7, and serve as indicators of environmental changes 5, 8 and 9.
Several studies have examined the responses of SMB and bacterial community structure to ecological restoration 4, 10, 11 and 12, but have primarily been focused on the ecological reconstruction and ecological renewal. However, little information is available about the impact of ecological natural restoration measures on SMB and bacterial community structure.
Closed-off management, an ecological restoration measures based on the Self-Design (Natural Restoration) theory (13), has been widely used to restore and protect ecosystem and resources (especially birds and fish). Closed-off management was relying on the natural power without human disturbance to restore ecology. Closed-off management was introduced into China by World Wide Fund for Nature and was implemented in core area of natural protection of many important wetlands, such as Poyang Lake (the largest freshwater lake in China), Dongting Lake (the second largest freshwater lake in China), Yangtze River (the longest river in China) delta, Yellow River (the second longest river in China) delta, and Hangzhou Bay. Dongting Lake is one of the important wintering habitats for international migratory birds and breeding and spawning grounds for migratory fish (14). To restore ecology and protect wildlife (especially birds, fish and wild animals), closed-off management has been implemented in part core area of natural protection of Dongting Lake wetland since 2006. Closed-off management caused changes in population and diversity of wildlife (birds, fish and wild animals), which would affect environmental conditions 15, 16 and 17. Accordingly, the closed-off management would affect SMB and bacterial community structure.
Seven years after the closed-off management begun, the possible consequences of the closed-off management can be assessed in Dongting Lake. In this study, we collected soil samples from the management area (MA) and contrast area (CA: human activities, such as hunting, fishing and draining, are permitted) and analyzed their soil properties, SMB, soil bacterial community structure and functional marker genes of nitrogen cycling. The objectives of this study were: (i) to analyze the responses of SMB and soil bacterial community to the ecological natural restoration measures (such as closed-off management) in Dongting Lake wetland; and (ii) to increase our knowledge on the relationship between soil properties, SMB, bacterial community and management in wetland.
Materials and methods
Study area
Dongting Lake (28°30′∼30°20′ N, 110°40′∼113°10′ E) is located in the middle reach of Yangtze River region and is the second largest fresh lake in China (18). The lake receives water from its four tributaries (Xiangjiang River, Zishui River, Yuanjiang River and Lishui River) and Yangtze River, and then empties into Yangtze River 1 and 9. The lake is characterized by a subtropical monsoon climate originating from the southeast Pacific Ocean and Indian Ocean (19). The monsoon-driven precipitation causes seasonal variability in the water level and area, with high water level and area in the wet season from May to October and with low water level and area in the dry season from November to the following April (1). The water area is 2691 km2 in the annual wet season and 710 km2 in the annual dry season (20). In dry season, the grasses expand along with the water level reduces, and provide abundant food for fauna and birds 1 and 21. Because of the wide variety of flora and fauna, especially birds, Easten Dongting Lake Nature Reserve was listed as one of the most important wetlands in Ramsar Convention in 1992 22 and 23.