Wetland vegetation biomass estimation and mapping from Landsat ETM data: a case study of Poyang Lake

Poyang Lake is the largest freshwater lake in China. This paper conducted a digital and rapid investigation of the lake’s wetland vegetation biomass using Landsat ETM data acquired on April 16, 2000. First, utilizing the false color composite derived from the ETM data as one of the main references, the authors designed a reasonable sampling route for field measurement of the biomass, and carried it out on April 18–28, 2000. Then after both the sampling data and the ETM data were geometrically corrected to an equal-area projection of Albers, linear relationships among the sampling data and some transformed data derived from the ETM data and the ETM 4 were calculated. The results show that the sampling data is best relative to the band 4 data with a high correlation coefficient of 0.86, followed by the DVI and NDVI data with 0.83 and 0.80 respectively. Therefore, a linear regression model, which was based on the field data and band 4 data, was used to estimate the total biomass of entire Poyang Lake, and then the map of the biomass distribution was compiled.

Iron Regulation of Wetland Vegetation Performance Through Synchronous Effects on Phosphorus Acquisition Efficiency

Iron-rich groundwater flowing into wetlands is a worldwide environmental pollution phenomenon that is closely associated with the stability of wetland ecosystems. Combined with high phosphorus(P) loading from agricultural runoff, the prediction of the evolution of wetland vegetation affected by compound contamination is particularly urgent. We tested the effects of anaerobic iron-rich groundwater discharge in a freshwater marsh by simulating the effect of three levels of eutrophic water on native plants(Glyceria spiculosa(Fr. Schmidt.) Rosh.). The management of wetland vegetation with 1–20 mg/L Fe input is an efficient method to promote the growth of plants, which showed an optimum response under a 0.10 mg/L P surface water environment. Iron-rich groundwater strongly affects the changes in ecological niches of some wetland plant species and the dominant species. In addition, when the P concentration in a natural body of water is too high, the governance effect of eutrophication might not be as expected. Under iron-rich groundwater conditions, the δ^(13)C values of organs were more depleted, which can partially explain the differences in δ^(13)C in the soil profile. Conversely, the carbon isotope composition of soil organic carbon is indicative of past changes in vegetation. The results of our experiments confirm that iron-rich groundwater discharge has the potential to affect vegetation composition through toxicity modification in eutrophic environments.

Spatiotemporal Variation of Land Use Pattern and Land Cover Changes in Gidan Kwano Watershed Area in North Central Nigeria

Land Management Systems (LMS) are institutional frameworks complex by the tasks they must achieve, national, cultural, political, and judicial settings and technology. The urbanisation process in Nigeria has increased since the 1960s because of the crude oil boom era and other government-backed industrial initiatives and investments. This study employed the use of both primary and secondary sources of data. Preliminary data comprise methods of land use, types of agricultural activities carried out and the process of working on the land by the farmers within a 10 km radius. The secondary data involved the interactive digital and visual techniques of the Geographical Information system for five seasons, with each having a ten-year interval span within 1975 to 2015. Statistical analysis was carried out with SPSS 2013 and XLSTAT 2015. Five land use and land cover types were observed within the Gidan Kwano watershed, which includes wetlands (WL), water bodies (WB), bare grounds (BG), vegetation (VG), and settlements (SL). The most prevalent landform in the study area during the 1975 period was the vegetative area which was 50% of the total landmass. Thus, the vegetation (VG) covered half of the Gidan Kwano watershed. However, the vegetative area decreased substantially during the study period of 1975 to 2015. It was observed that the vegetation (VG) within the study area had the highest percentage of coverage, of 34%. During the study period, a significant decrease was observed in the WL, WB and VG areas. It was also concluded that due to the built-up places, the infiltration of surface runoff from rainwater would be drastically reduced as most of the sections are paved for construction activities while a section of the study area is covered with rock outcrops and farmlands.