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Deng M.,Key Laboratory of Biodiversity Conservation in Southwest China | Deng M.,Southwest forestry University | Tian K.,Key Laboratory of Biodiversity Conservation in Southwest China | Tian K.,National Plateau Wetland Research Center | And 3 more authors.
Journal of Ecology and Rural Environment | Year: 2010

With the aid of the 3S-technique and Fragstats software, the interpretation images (TM) of the plateau wetland reserve in 1990, 2000 and 2007 were analyzed for quantitative variation of the landscape thereof and its driving factors. Results show that degraded marsh is the background landscape of the reserve, accounting for 48.05% of the study area in 2007. During the first 10 years (1990-2000) after the establishment of the reserve, lakes, rivers and marshs therein decreased in area and evoled mainly to degraded marshes and meadows. The area of degraded marsh, meadows and shrubberies increased by 1 978. 60, 2 559. 09 and 824. 27 hm2, respectively; the number of patches and the heterogeneity and fragmentation degree of the landscape decreased; and the polymerization degree and dominance increased. After the establishment of the reserve (2000-2007) , the area of rivers was restored slightly. However, wetland degradation was still the main trend; the areas of lakes and marshes kept on decreasing while the area of meadow increasing; the area of denes increased by 1 929. 00 hm; the spatial heterogeneity and fragmentation degree of the landscape and the number of patches increased, while the polymerization degree and dominance decreased. Natural factors like global warming coupled with artificial ones, like drainage, over-grazing, disorderly tourism and construction of infrastructure were the main driving factors of wetland degradation. Source


Tan R.,Southwest forestry University | Li W.,Yunnan Academy of Biodiversity | Wang J.,Yunnan Academy of Biodiversity | Du F.,Southwest forestry University | Yang Y.,National Plateau Wetland Research Center
Proceedings of the 2013 3rd International Conference on Intelligent System Design and Engineering Applications, ISDEA 2013 | Year: 2013

Ecological niches remain central to explaining community structure, and niche-based studies have helped us to better understand species interactions, distributions, coexistence and the associated mechanisms. However, most of these studies focus on terrestrial plants, and few studies have explicitly quantified niche parameters of plateau wetland plants. Also, although understanding the effects of disturbance on niche breadth and overlap is vital to developing a basic understanding of species dynamics, response strategies and distribution patterns, few studies have tested explicitly disturbance effects at different seasons. Our study sites are set up in Napa Wetland, Shangri-la, located at the southeastern margin of the Tibetan Plateau. Recently, wetland loss and degradation has become a serious local problem, mainly due to three types of disturbance, tourist trampling, anthropological grass removal, and pig forage. The main purpose of our study is to investigate the effects of different types of disturbance on niche parameters of dominant wetland plant species. We chose research sites under different disturbance regimes, and surveyed selected sites during May, July and October in 2011, with 3 replicates for each disturbance regime. Our results showed that there was a seasonal variation in species niche breadth under different disturbance regimes. Similarly, niche overlap and niche differentiation also altered with seasonal changes, with the lowest niche overlap and the highest niche differentiation occurring in spring and fall, whereas the highest niche overlap and the lowest niche differentiation occurring in summer. Our results thus provide important information in regard to plant community composition, structure and dynamics in Napa Wetland under different disturbance regimes, and help to further explore the mechanisms by which dominant wetland species coexist, and their response patterns to varying disturbance forms in the long term. © 2012 IEEE. Source


Li N.,Yunnan Academy of Forestry | Li N.,National Plateau Wetland Research Center | Yuan H.,Southwest forestry University | Tian K.,National Plateau Wetland Research Center | Peng T.,Southwest forestry University
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

The wetland landscape dynamics and its environmental effects have been considered as a research hotspot. But researches about soil carbon pool changes driven by landscape pattern changes were rarely seen. To address this issue, a study was carried out in the Napahai wetland, a sensitive region of global changes in northwestern Yunnan, adopting the In-situ intact soil sampling methodology and supported by the "3S" tools. Results showed that the landscape altered significantly within 26 years. Compared with 1974a, the fragmentation of Napahai landscapes was increasing, the landscape shapes became more complicated, dispersed, and dominated by large patches, the matrix of the Napahai landscapes has been converted from wetland types to the ever-increasing human land use types. At the land level,the patch number and landscape shape index increased 42% and 12. 19% by 1994, as well as 40% and 1.02% by 2000. The aggregation index decreased 0. 56% (by 1994) and 0. 52% (by 2000). Landscape diversity and landscape dominance firstly increased 0. 844% and 0. 847% by 1994 and then decreased 3. 130% and 3. 134% by 2000. At the class level, the changes of wetland types trended to complexity, the area percentage of water body, marsh and swampy meadow increased form 70. 29% (1974) to 72. 20% (1994) then decreased to 48. 79% (2000), however, that of meadow and farmland decreased a bit in 1994 then largely increased in 2000a. The landscape pattern changes of the wetland had impacts on the wetland's soil carbon storage fluctuation. Responding to the landscape area changes, soil carbon storage increased from 33. 46×10 4t (1974) to 36. 91×10 4t (1994) and then decreased to 32. 92×10 4t (2000). With the landscape type transformations, the soil carbon sequestration and emission form 1974 to 1994 reached respectively 6. 08×10 4t and 2. 63×10 4t. The soil carbon sequestration form 1994 to 2000 reached 2. 01×10 4t, nonetheless, the emission increased sharply, which is up to 2. 28 times of that of 1974-1994. The landscape pattern changes, the soil carbon storage and its "source/sink" shifts have been imposed by both natural factors and human impacts. Under the context of geology, hydrology and climate changes, human disturbances such as wetland drainage, reclamation, overgrazing, and vegetation destruction of catchments have further intensified the changes of wetland. Source


Xie C.J.,Southwest forestry University | Xie C.J.,National Plateau Wetland Research Center | Lian X.G.,Southwest forestry University | Lian X.G.,National Plateau Wetland Research Center | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

Nitrogen (N) is an essential nutrient of special importance for plant growth while it is often deficient in soils because of low phytoavailability. Shifts in soil N status can be caused by variations in the N transformation. Soil N mineralization is of prime importance in ecosystem productivity, N potential availability and losses from ecosystems. Using resin-core incubation method, we examined the net N mineralization rates in swamp, swamp meadow and meadow soils (0-15 cm) in situ. The soils located along a water level gradient in Napahai wetland, which are sensitive to the changes of hydrological regimes, and reflect the different stage of wetland succession. The objective was to provide insight into the mechanism that how wetland ecosystem evolution constraining net N mineralization in soils. The results indicated that the inorganic N concentrations were significantly different among the three soils (0-10 cm), swamp > swamp meadow > meadow, during the growth season. The NH4 -N concentrations showed the same decrease trend as inorganic N while the NO- 3 -N concentrations showed a significant increase trend in the three soils., The inorganic N was mainly in the form of NH+ 4 -N in swamp and swamp meadow soils, which accounted for 96.76% and 75.24% respectively. In contrast, NO- 3 -N was the main form of inorganic N in meadow soil and accounted for 58.77%. The net N mineralization rates were significantly different during the growth season, ranking in order of swamp meadow > meadow > swamp. The results indicated that wet and dry alternation is beneficial to the net N mineralization in the wetland soils, and favors higher N effectiveness and greater phytoavailability. The net N mineralization rate in swamp soil was negative during the growth season. The rates in swamp meadow and meadow soils were negative from May to September while positive from September to November. The net ammonization rates in the soils showed a significant decrease as meadow > swamp meadow > swamp from May to September, but showed a significant increase as swamp < meadow < swamp meadow from September to November. The net nitrification rates in soils among the three wetland types showed a significant decrease as swamp > swamp meadow >meadow from May to September, but showed a significant increase as swamp < swamp meadow < meadow from September to November. On the whole, the net N mineralization was main in the form of nitrification in the swamp and meadow soils while in the form of ammonization in the swamp meadow soil during the growth season. In addition, the N mineralization in soils was influenced by soil NO3 -N concentration, organic material concentration, C/N ratio and soil moisture in the soils. The net N mineralization rate in swamp soil was negatively related to soil NO- 3 -N concentration, organic material concentration, C/N ratio and soil moisture. In swamp meadow soil, the N mineralization rate was negatively related to soil NO- 3 -N concentration and C/N ratio, but was positively related to soil moisture. In contrast, the net N mineralization rate in meadow soil was negatively related to soil NO- 3 -N concentration and bulk density, but was positively related to organic material concentration and soil moisture. Source

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