Abstract:Using the CO₂ flux data measured by the eddy covariance method in the northeast of Qinghai-Tibetan Plateau in 2005, we analyzed the carbon flux dynamics in relation to meteorological and biotic factors. The results showed that the alpine wetland ecosystem was the carbon source, and it emitted 316.02 gCO₂·m^-2 to atmosphere in 2005 with 230.16 gCO₂·m^-2 absorbed in the growing season from May to September and 546.18 gCO₂·m^-2 released in the non-growing season from January to April and from October to December. The maximum of the averaged daily CO₂ uptake rates and release rates was (0.45 ± 0.0012) mgCO₂·m^-2·s^-1 (Mean ± SE) in July and (0.22 ± 0.0090) mgCO₂·m^-2·s^-1 in August, respectively. The averaged diurnal variation showed a single-peaked pattern in the growing season, but exhibited very small fluctuation in the non-growing season. Net ecosystem exchange (NEE) and gross primary production (GPP) were all correlated with some meteorological factors, and they showed a negatively linear correlation with aboveground biomass, while a positive correlation existed between the ecosystem respiration (R_es) and those factors.

Abstract:As one of the important ecosystem services of wetlands, carbon sequestration potential of lakes and swamps in China were investigated. Significant differences were found among the carbon sequestration potential of various lakes, determined by natural conditions and human disturbance. In this study, swamps had a carbon sequestration potential of 4.90 TgC, much higher than lakes in China. Mangrove and coastal marsh have the highest carbon sediment rate among swamps. Carbon sequestration potential in returning farms to lakes and swamps was 30.26 and 0.22 GgC·a^-1, respectively. Under the ongoing national wetland conservation action plan in China, the carbon sequestration potential of wetland restoration was 6.57 GgC·a^-1. Protection and restoration measurements can improve carbon sequestration potential of wetlands.

Abstract:16S rDNA sequencing method is one of the effectively used culture-independent techniques in recent years. In this study, 16S rDNA sequencing method was used to investigate the bacterial diversity in deep-sea sediment from northeastern Pacific polymetallic nodule province. Total DNAs were extracted by using 2 different methods (chemical method and DNA extracting kit method). After purification, genomic DNA was amplified by using 2 universal primers (27F and 1492R). Clones were selected and sequenced randomly. After the sequences were checked by using the Chimera Check Program of the RDP database, a bacterial 16S rRNA gene library of 79 clones was established. Phylogenetic analysis indicated that 79 clones could be divided into 11 phylotypes. Gamma Proteobacteria (22.8%) and alpha Proteobacteria (16.5%) were the dominant components of the sediment bacterial community, followed by Planctomycetacia (7.6%), delta Proteobacteria (6.3%), Nitrospira (6.3%), Actinobacteria (6.3%), beta Proteobacteria (5%), Acidobacteria (5.1%), Sphingobacteria (3.8%), Firmicutes (2.5%) and uncultured bacteria (17.7%). Gamma Proteobacteria also dominated at slices 0–2 cm and 4–6 cm. Different slices had different types of bacteria, alpha Proteobacteria, gamma Proteobacteria, delta Proteobacteria, Planctomycetacia, Nitrospira, Actinobacteria and Acidobacteria, however, appeared in all slices. Pseudomonas is common in many different deep-sea environments. In this study, it accounted for 22.2% of the total gamma Proteobacteria.

Abstract:Photosynthesis coupled with transpiration determines water use efficiency (WUE) at leaf level, and the responses of WUE controlled by gas exchanges through stomata to environment are the basis of carbon and water cycles in the ecosystem. In this paper, by using Li-6400 Portable Photosynthesis System (LI-COR), WUE at leaf level was analyzed under controlled photosynthetic photons flux density (PPFD) and CO₂ concentration conditions across 9 plant species including maize (Zea mays), sorghum (Sorghum vulgare), millet (Setaria italica), soybean (Glycine max), peanut (Arachis phyogaea), sweet potato (Ipomoea batatas), rice (Oryza sativa), Masson pine (Pinus massoniana) and Schima superba. We had developed a new model to estimate the water use efficiency in response to the combined effects of light and CO₂ concentration. Our measured data validated that this model could simulate the changes of water use efficiency very well under combined effect of light and CO₂ concentration. It could be used to estimate contribution of photosynthesis increase and transpiration decline on water use efficiency with the rising of CO₂ concentration. Great differences in water use efficiency occurred in these different plant species under various CO₂ concentration levels. Based on water use efficiency at regional scale, we concluded that plants should be separated into C₃ plants and C₄ plants, and furthermore, C₃ plants should be separated into herbaceous plants and woody plants. Our separation criteria would do a great favor in modeling the evapotranspiration of terrestrial ecosystem with carbon and water balance.

Abstract:Conservation effectiveness of wetland nature reserves is determined by both the management intensity inside the reserves and the hydrological status outside the reserves. Therefore, differences of ecological functions inside and outside the reserves are an integrated indictor for assessing conservation effectiveness. Based on the land use map created from Landsat-TM satellite image and 1:50000 Digital Elevation Model (DEM) data in the study area, the catchments that belong to the wetland reserves were determined as their hydrological sensitive zones by SWAT (Soil and Water Assessment Tool) hydrological model. The ecological function indices of wetland reserves and their corresponding hydrological sensitive zones were calculated through expert consultation and value assessment on wetland ecosystem service functions. The results showed that the ecological functions of national wetland reserves were better than those of local reserves in general. However, the wetland ecological functions of hydrological sensitive zones of the former were not always better than those of the latter. Meanwhile, clustering analysis showed that the wetland ecological functions of several adjacent reserves in Nongjiang-Bielahonghe watershed were similar. But correlation analysis found that there existed a remarkable positive correlation between the wetland ecological function indices of local reserves and their hydrological sensitive zones.

Abstract:Sandy desertification is now the main ecological problem in the Otindag Sandy Land. In order to reveal the process of land degradation, especially the latest situation of sandy desertification, a method integrating remote sensing, Geographic Information System (GIS) and field survey was employed to build a sandy desertification dataset for analysis. Remote sensing images included the Landsat Thematic Mapper (TM) image in 1987, the Enhanced Thematic Mapper Plus (ETM ) image in 2000, and the image with the Charge-Coupled Device Camera (CCD) on the China-Brazil Earth Resources Satellite (CBERS) in 2006. Five land-cover classes, including active sand dunes, fixed sand dunes, semi-fixed sand dunes, inter-dune grassland and wetlands, were identified. Results showed that the Otindag Sandy Land has been suffering sandy desertification since 1987 with 2 different desertified stages. The first stage from 1987 to 2000 was a severe sandy desertification period, characterized by the fixed sand dunes decreasing at a high speed, and the semi-fixed and active sand dunes increasing remarkably. The second stage spanned from 2000 to 2006 and the sandy desertification was weakened greatly. Although a large area of fixed sand dunes were transformed to other types, fixed sand dunes were still the dominant type in the Ointdag region at 2006. Spatial change detection based on active sand dunes showed that the expansion area was much larger than the reversion area in the past two decades, and that several active sand belts had been formed, suggesting that sandy desertification controlling of the Otindag Sandy Land will be a long-term task.

Abstract:Ecological-niche factor analysis (ENFA) is a multivariate approach to study geographic distribution of species on a large scale with only “presence” data. It has been widely applied in many fields including wildlife management, habitat assessment and habitat prediction. In this paper, this approach was applied in habitat suitability assessment for giant pandas in Pingwu County, Sichuan Province, China. With “presence” data of giant pandas and remote sensing data, habitat suitability of pandas in this county was evaluated based on ENFA model, and spatial distribution pattern of nature reserves and conservation gaps were then evaluated. The results show that giant pandas in this county prefer high-elevation zones (> 2128 m) dominated by coniferous forest, and mixed coniferous and deciduous broadleaf forest, and avoid deciduous broadleaf forest and shrubs. Pandas avoid staying at habitats with human disturbances. Farmland is a major factor threatening panda habitat. Panda habitat is mainly distributed in north and west of Pingwu with a total area of 234033 hm², 106345 hm² for suitable habitat and 127688 hm² for marginally suitable habitat). 3 nature reserves were located in Pingwu, covering over 49.2% of total suitable habitat and 45.6% of total marginally suitable habitat. Although 47.2% of panda habitat was in reserves under protection, connectivity between reserves was weak and a conservation gap existed in the north part of Pingwu. Thus, a new nature reserve in Baima and Mupi should be established to link the isolated habitats.