This paper evaluated changes in vegetation from 2000 to 2012, based on 1-km resolution 16-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) Normalised Difference Vegetation Index (NDVI), and related them to changes in estimates of human disturbance on the rangelands of the Qinghai-Tibet Plateau. The main rangeland types studied were desert, steppe and meadow with the latter mainly found in the southern and eastern parts of the study area. The results indicated that human disturbance was distributed mainly in the southern and eastern parts of the study area and corresponded with high NDVI values. The NDVI values showed an upward trend over the study period, with 28.5% of the study area exhibiting a significant increase. The proportion of rangelands that experienced a downward trend in NDVI increased as the level of human disturbance increased. Of the different rangeland types, meadow had the highest NDVI values, the greatest human disturbance, and the highest proportion of rangelands that exhibited a significant decrease in NDVI. Compared with areas with no human disturbance, meadow and steppe rangelands that experienced an increase in human disturbance had lower rates of increase in their NDVI values but, conversely, desert rangelands showed the opposite trend. In addition, it was found that precipitation had the dominant influence on NDVI values and that higher precipitation and slighter lower temperatures over the period of the study were related to an increase in NDVI values.
The structure and function of aquatic communities in reservoir ecosystems can be strongly affected by dam construction. The Ecopath model is an effective tool that reveals the food web structure and pathways of energy flows. In this study, it was applied to analyze the trophic interactions and energy flows within the Manwan reservoir ecosystem on Lancang River in southwest China. Ecotrophic efficiency (EE) was calculated and the value of EE was 0.073 for the least-exploited piscivorous fishes (top predators) and 0.93 for the most-exploited zoobenthos. Four estimated trophic levels of the groups varied from 1 for detritus and phytoplankton (level I) to 3.69 for piscivorous fishes (level IV) and the remaining groups were mainly at trophic levels II and III. Food web structures and interactions were well represented by a linear food chain that was dominated by a detritus pathway; that is, energy flows from detritus were as important as phytoplankton in the web. The proportion of total energy flow originating from detritus was 46% while the other 54% came from primary producers. The average transfer efficiencies between trophic levels were 16.6% from primary producer and 15.7% from detritus. Total system throughput was found to be 5550 t km−2 yr−1, total primary production/total respiration ratio was 2.46, and the ascendency index was 27.4%. These results showed that Manwan reservoir ecosystem was an immature ecosystem and still at its development stage. These results are helpful for biodiversity preservation and the understanding and monitoring of reservoir ecosystems which are key resources for fish and other aquatic organisms.
Protected areas (PA), especially montane forests, have been identified as an essential tool for conserving biodiversity and as key sources of ecosystem services, which include Net Primary Productivity (NPP), carbon sequestration, habitat and shelter for endemic and endangered species, and clean water. However, forests are threatened constantly by human impacts like forest fires, air pollution, clearing for agricultural uses, and illegal cutting. Despite those benefits, conservationists are far from able to assist all those natural wonders under threat due to the lack of funding for research and other related conservation projects. Therefore, one of the six key landscapes identified for conservation in the Albertine Rift known as montane forest Nyungwe National Park (NNP) located in Rwanda, its forest degradation and its canopy daily net primary productivity and carbon sequestered were assessed and evaluated using remote sensing and ArcGIS techniques combined with a light use efficiency model. To carry out this study, freely available dry season Landsat Thematic Mapper (TM) images were downloaded from the U.S. Geological Survey Global Visualization Viewer along with Rwanda Digital Elevation Model (DEM). Landsat TM images data were processed through radiometric correction, dark object subtraction, then masked and geo-referenced to NNP. Based on ground knowledge and features such as wetlands and infrastructure e.g., roads and buildings, Regions Of Interest (ROI) were used for training data for supervised maximum likelihood classification where all spectral bands in each satellite image were used, then classified into three land cover types using Envi 4.7 image processing software. Through raster calculator ArcGIS 10.1 tool, the most commonly used vegetation indices, Normalized Difference Vegetation Index (NDVI) and its time series change detection analysis from 1986 to 2010 were performed, but also resampling and surface analysis techniques were executed on DEM. The land cover classes, as revealed by the processed satellite images, showed that 92.4% of forestland has undergone degradation from 1986 to 2010. The highest forestland downsizing rate of 4.5% was observed between 1986 and 1994. The entire park has lost up to 40% of its daily NPP and carbon sequestration capacity between 1986 and 2010. The study also revealed that the degradation was evenly distributed across the entire area of the park, which negatively affects endemics and endangered species of this park through lack of alternative habitat once one habitat becomes less suitable. Thus, the present study suggests further investigation of climatic variables, conditions, and anthropogenic threats, which may impact interpretations of the sources of this forest coverage degradation. The results of this study show that cost and time effective biodiversity information technology research tools, namely remote sensing and GIS, can effectively and accurately document time series forest degradation with associated factors and also assist in assessing the ecosystem services.
Taking road network in Longitudinal Range-Gorge Region(LRGR) as an case study,we got the bound of road-effect zone through overlay method of GIS considering its influencing factors.Then we calculated the percentage of road-effect zone area in certain region and study the spatial variability in LRGR.Further,road density,population density,village number,ecological capacity and average altitude were selected to analyze their relationship with road effect zone.The results showed that different road types had various road-effect zones.Spatial contribution of road effect showed a great regional difference.The effect zone decreased from Kunming to region around.Honghe River Valley had a higher value than Lancang and Nujiang River Valley.In LRGR,there showed significant spatial convergence region in east,north and south-west of LRGR.Correlation analysis showed that there existed significant correlation between road-effect proportion and road density,population density,village number,ecological capacity while no correlation with average altitude.
Irrational land use and human disturbance accelerate soil erosion and land degradation in the areas with vulnerable ecology in the transitional zone between the Loess Plateau and the Mu Us Sandland.In this paper,the effects of road networks on the ecological security in this transitional zone in north Shaanxi Province are researched.In the study,the difference in terrain,landforms,ecosystems and landscapes is significant,the ecological environment is vulnerable and is strongly affected by human activities.Road construction in the study area has the social effects and economic returns,especially affects significantly the ecology.As widespread features of landscapes and human disturbance paths,road networks bring about many ecological effects and affect the regional land ecological security.Focused on the impact of road networks on landscapes,in this paper the relationship between road networks and land ecological security is discussed.Based on the different ecological patterns and processes,the pattern-and process-based ecological security indexes are put forward,and then the various potential and accumulative ecological effects of road networks are comprehensively assessed.Furthermore,the effects of road networks on land ecological security are analyzed.A case study on the road effects on land ecological security in Hengshan County in north Shaanxi Province is carried out.The results show that the spatial difference of ecological security affected by roads is significant,and there is a high negative correlation between the road density and the ecological security level.
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