Changes in vegetation cover and landscape fragmentation in the Panidihing Bird Sanctuary, India

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m−2 decade−1 regionally) compared to the CCCMA (+1.3 W m−2 decade−1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (−0.2 to −0.3 W m−2 decade−1). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m−2 decade regionally in the ECHAM scenario compared to +0.76 W m−2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Abstract. We present a numerical modeling investigation into the interactions between transient climate and vegetation cover with hillslope and detachment limited fluvial processes. Model simulations were designed to investigate topographic patterns and behavior resulting from changing climate and the associated changes in surface vegetation cover. The Landlab surface process model was modified to evaluate the effects of temporal variations in vegetation cover on hillslope diffusion and fluvial erosion. A suite of simulations were conducted to represent present-day climatic conditions and satellite derived vegetation cover at four different research areas in the Chilean Coastal Cordillera. These simulations included steady-state simulations as well as transient simulations with forcings in either climate or vegetation cover over millennial to million-year timescales. Two different transient variations in climate and vegetation cover including a step change in climate or vegetation were used, as well as 100 kyr oscillations over 5 Myr. We conducted eight different step-change simulations for positive and negative perturbations in either vegetation cover or climate and six simulations with oscillating transient forcings for either vegetation cover, climate, or oscillations in both vegetation cover and climate. Results indicate that the coupled influence of surface vegetation cover and mean annual precipitation shifts basin landforms towards a new steady state, with the magnitude of the change being highly sensitive to the initial vegetation and climate conditions of the basin. Dry, non-vegetated basins show higher magnitudes of adjustment than basins that are situated in wetter conditions with higher vegetation cover. For coupled conditions when surface vegetation cover and mean annual precipitation change simultaneously, the landscape response tends to be weaker. When vegetation cover and mean annual precipitation change independently from one another, higher magnitude shifts in topographic metrics are predicted. Changes in vegetation cover show a higher impact on topography for low initial surface cover values; however, for areas with high initial surface cover, the effect of changes in precipitation dominate the formation of landscapes. This study demonstrates the sensitivity of catchment characteristics to different transient forcings in vegetation cover and mean annual precipitation, with initial vegetation and climate conditions playing a crucial role.

Rapid urban growth has become one of the key global drivers of land-use change, significantly impacting the natural environment, particularly vegetation cover. This research focused on quantifying and analyzing the spatial and temporal change of urban growth and its consequent effects on the city’s vegetation cover, assessing the loss and degradation of vegetation cover, and identifying the factors contributing to changes in land use and vegetation. The research problem was the limitation in the way of understanding the spatiotemporal changes in vegetation cover due to urban growth in Kigali city. Therefore, this research was focused on the main objective which was to assess the spatiotemporal change of urban expansion on vegetation cover, a case of Kigali city. Specific objectives were: assessing the driving factors of urban expansion in Kigali city, to analyze the variation change in vegetation cover in Kigali city over twenty-four years and to examine the relationship between urban expansion and vegetation loss in Kigali city. The methods used were library research by reading different books, papers and journals, which helped the researchers to do literature review. Household surveys helped to understand how urban expansion impacts local residents' access to green spaces, environmental changes, and their general perceptions of vegetation loss. Satellite imagery from multiple time frames, processed using advanced GIS and remote sensing techniques, were used to analyze land use/land cover changes, with a focus on vegetation loss and the spatial-temporal dynamics of urban growth. Key informants' interviews provided in-depth, qualitative insights that complemented quantitative data from satellite imagery and GIS analysis. The results provided detailed maps of urban sprawl and vegetation cover changes in Kigali, with a focus on highlighting areas most vulnerable to degradation. Different main drivers of urban change such as population growth, economic development and rural-urban migration have been discussed. To sum up, the study found a significant decrease in vegetation cover over the past 24 years, a percentage of 90% caused by vegetation loss such as urban expansion, deforestation and poor urban planning, while a smaller percentage of 10% noted some efforts to increase vegetation through reforestation and green infrastructure projects land use and zoning regulation and the relationship between urban expansion and vegetation cover has shown that if urban growth is done in a sustainable way vegetation cover can be protected

Since the 1970s, a breeding colony of lesser snow geese (Chen caerulescens caerulescens L.) at La Pérouse Bay, Manitoba, has grown 8% annually. This increase has led to significant loss of plant cover in all major salt- and freshwater coastal habitats between 1976 and 1997. A series of transects established in 1976 was resurveyed in 1997. Exposed sediment, extent and type of vegetative cover, and aquatic areas were recorded along transects using a classification of 12 a priori classes. Five regions within the colony were identified, and changes in vegetation cover differed among these and depended on unique combinations of vegetation class and year. Grubbing by geese has led to loss of graminoid plants, especially in intertidal and supratidal marshes. Exposed sediments have largely replaced previously vegetated areas since 1976. Species characteristic of disturbed sites have colonized exposed sediment with the most abundant species varying according to soil conditions. In intertidal marshes, willow cover declined in association with the development of hypersalinity after loss of the graminoid mat, but willow cover increased at the base of well-drained beach ridges and in a river delta with ample winter snow accumulation and freshwater flow in spring that protected ground vegetation. Most of the expected successional trends associated with isostatic uplift and changes in soil organic matter failed to occur because of intense goose foraging throughout the 20 years. The likelihood of sustained recovery of plant communities in the immediate coastal zone is very low, as long as goose numbers continue to increase. Indirect effects of vegetation loss (e.g., hypersalinity) and subsequent erosion of exposed sediments following grubbing will delay plant colonization and retard succession.

Images from medium-resolution satellites are frequently used to study changes in urban vegetation or impervious surface cover over relatively long time periods. In this paper, we applied both “hard” and “soft” mapping methods on two images covering the Brussels Capital Region in a time span of roughly 20 years. Although soft approaches are more accurate because they take the occurrence of mixed pixels into account, errors that result from the application of sub-pixel proportion estimation methods nevertheless propagate if the maps are used for change analysis. In this paper, we propose a method to take uncertainty in sub-pixel classification into account when producing change maps.

Impacts on watershed-scale runoff and sediment yield resulting from synergetic changes in climate and vegetation

Diagnosing climate variability and environmental change in floodable regions is essential for understanding and mitigating impacts on natural ecosystems. Our objective was to characterize environmental degradation in the Brazilian Pantanal by identifying changes in vegetation and water cover over a 30-year period using remote sensing techniques. We evaluated surface physical–hydric parameters, including Land Use and Land Cover (LULC) maps, Normalized Difference Vegetation Index (NDVI), Modified Normalized Difference Water Index (MNDWI), Normalized Difference Moisture Index (NDMI), and precipitation data. There was a decrease in the area of water bodies (−9.9%), wetlands (−5.7%), and forest formation (−3.0%), accompanied by an increase in the area of pastureland (7.4%). The NDVI showed significant changes in vegetation cover (−0.69 to 0.81), while the MNDWI showed a decrease in water surface areas (−0.73 to 0.93) and the NDMI showed a continuous decrease in vegetation moisture (−0.53 to 1). Precipitation also decreased over the years, reaching a minimum of 595 mm. Vegetation indices and land use maps revealed significant changes in vegetation and loss of water bodies in the Pantanal, reinforcing the need for sustainable management, recovery of degraded areas, and promotion of ecotourism to balance environmental conservation and local development.

Coal mining will change the land nutrient conditions and affect the growth of surface vegetation. In view of the lack of analysis and research on the spatio-temporal changes of vegetation coverage in Yungang District, Shanxi Province, in the hinterland of Datong coalfield, deeply explored the vegetation index information from remote sensing data and conducted statistical analysis of vegetation time series. Based on landsat8 oli images from 2019 to 2022, the normalized difference vegetation index (NDVI) , vegetation coverage and greenness change rate were extracted, and the long-term vegetation coverage types, vegetation coverage and vegetation coverage changes in Yungang district were mined from the vegetation index, so as to study the distribution characteristics and changing trend of vegetation in Yungang district. The results show that: (1) the surface vegetation in the mining area is mainly cultivated land, shrubs and trees, and the overall vegetation coverage is high. The vegetation change trends in the Northwest Mountainous Area and the southeast plain area divided by the Kouquan fault zone are quite different. From 2019 to 2022, the dominant surface vegetation types in the Northwest Mountainous area gradually change from shrubs and trees to shrubs and grassland, and the vegetation coverage changes from high to medium-high to medium, and the surface vegetation coverage types in the southeast plain area change little, and the vegetation coverage degrades slightly. (2) From 2019 to 2022, the degraded area of vegetation coverage in Yungang district is 40%, the basically unchanged area is 37%, and the improved area is 23%. Mining and farmland harvesting have a significant negative impact on vegetation, while mining area greening and farmland planting have a significant positive impact on vegetation. In the next step, it is necessary to continuously monitor the dynamic changes of vegetation in Yungang District, and study the relationship between vegetation changes and mining and ecological restoration, to provide data support for guiding the ecological construction of the whole region.

Constantly increasing vegetation changes pose serious challenges to the sustainable use of global ecosystems. Thus, facing the increasingly serious climate and ecological environment problems and improving vegetation coverage is crucial to the sustainable development of the region. Along these lines, in this work, a monitoring model of vegetation cover change was proposed and developed by using Landsat TM (1989, 1999, and 2011) and Landsat OLI-TIRS (2021) data. More specifically, it was used to assess vegetation change. Based on this model, the vegetation change in the core area of Hulun Buir Grassland was systematically analyzed., From the acquired results, the existence of spatial differences in the vegetation coverage changes in the study area were demonstrated. The total area of vegetation coverage changes was 758.95 km2, and the area from low vegetation coverage to high vegetation coverage was 456.41 km2, accounting for 60.14% of the total change area. The area from high vegetation coverage to low vegetation coverage was 302.57 km2, accounting for 39.86% of the total change area, whereas the area of the area without vegetation coverage was 1963.92 km2, accounting for 72.13% of the study area, and the overall vegetation coverage is improving. Vegetation cover change monitoring models can also be used to reveal and describe large-scale vegetation landscape changes and obtain clear vegetation change results through easy-to-obtain data; our work suggests that in the process of pursuing regional economic development and accelerating urbanization, industrialization, and agricultural modernization, human beings should assume more responsibilities and pursue the sustainable development of the natural environment. The results of this work are of great importance to further study the potential driving mechanism of the vegetation coverage changes and provide theoretical guidance for relevant managers to formulate vegetation restoration measures.

PDF HTML阅读 XML下载 导出引用 引用提醒 1994-2016年和田绿洲植被覆盖时空变化分析 DOI: 10.5846/stxb201805281167 作者: 作者单位: 新疆大学资源与环境科学学院,新疆大学资源与环境科学学院,新疆大学资源与环境科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41761019，41061052）；西部地区人才培养特别项目（201408655089） Spatio-temporal variations in vegetation cover in Hotan Oasis from 1994 to 2016 Author: Affiliation: College of Resources and Environmental Science,Xinjiang University,,College of Resources and Environmental Science,Xinjiang University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:监测植被变化对评价区域生态环境质量及生态过程具有重要意义。基于Landsat数据影像，运用归一化植被指数、像元二分模型、重心迁移模型等方法分析和田绿洲植被覆盖时空变化。结果表明：（1）和田绿洲植被分布总体以玉龙喀什河和喀拉喀什河为轴线，从高到低向外展布，高覆被以大面积片状集中于绿洲中部，低、中覆被相对零散围绕高覆被分布；（2）过去23年，和田绿洲植被覆盖面积和植被覆盖度均呈升高趋势。2016年相比1994年，绿洲植被覆盖面积增加553 km2，增长了19.6%；（3）和田绿洲覆被变化存在阶段性和区域性差异。时段上，2000-2005年覆被面积增加最明显；区域上，西部覆被增加最显著；（4）气候变化对和田绿洲覆被变化存在一定影响，但人类活动影响最直接。其中耕地开垦、作物种植是和田绿洲覆被增加的最主要因素，而城市基建是引起绿洲覆被减少的最主要因素。同时，因农耕区水耗增加挤占天然覆被生态用水，引起天然覆被退化，威胁绿洲未来发展；（5）过去23年，绿洲覆被重心整体西移。 Abstract:It is of significance to monitor the changes in vegetation in the assessment of regional ecological environment quality and ecological process. The typical Hotan Oasis in the arid region of Northwestern China was selected as the study area. Based on Landsat remote sensing images, the temporal and spatial changes in the vegetation cover in Hotan Oasis were analyzed using NDVI, binary dichotomy, and gravity center migration models. The aim of this study was to understand the characteristics of vegetation cover changes in the oasis during recent decades. The results demonstrated that the vegetation distribution in Hotan Oasis is generally distributed from high to low on the axis of Yulongkash and Karakash Rivers. The high vegetation cover is concentrated in the middle of the oasis, whereas, the high vegetation is surrounded by relatively the low and medium vegetation. During the past 23 years, the vegetation-covered area and vegetation coverage of Hotan Oasis have increased significantly. In 2016, compared with that in 1994, the vegetation-covered area has increased by 553 km2, an increase of 19.6%. In terms of different levels of vegetation cover changes, high vegetation cover increased significantly, with an increase of 897 km2 (83.6%) during the past 23 years. The fluctuation and change in medium vegetation cover were obvious. In 2016, compared with that in 1994, the area decreased by 103 km2 (9.3%); low vegetation cover significantly reduced, with a decrease of 241 km2 (38%) during the past 23 years. There are time-phased and regional differences in the spatial changes in the coverage of Hotan Oasis. In terms of area change, from 2000 to 2005, the area of oasis vegetation cover increased most obviously. In terms of regional changes, the vegetation coverage in the west and east of the oasis increased most significantly, and the urban areas and nearby areas of Hotan City, Moyu County and Lupu County decreased significantly. The expansion of cultivated land is the main cause of changes in oasis cover. However, the reclamation of natural grassland will reduce the ecological effects of the oasis, which will threaten the ecological stability and sustainable development of the oasis in the long term. As a whole, over the past 23 years, the center of gravity of oasis cover has moved westward. 参考文献 相似文献 引证文献

Quaternary interglacials show varying amplitudes and different patterns of changes in climate and vegetation cover. A better understanding of these changes requires deeper insight into the mechanisms by which climate and vegetation interact. Using the Earth system model CESM1.2, the present study assesses the role of Northern Hemisphere vegetation changes in shaping the global climate for different interglacial warm intervals: the mid Holocene (MH; 6 ka), the Last Interglacial (LIG; 127 ka), and Marine Isotope Stage 11 (MIS 11; 409 ka). The model allows the prognostic and interactive simulation of leaf and stem area indices and vegetation height, while the vegetation biogeography is fixed (“semi-dynamic vegetation”). In accordance with previous studies, we find that the simulated interglacial climates turn out to be too cold compared to reconstructions. Relative to the pre-industrial (PI) control run, the annual global mean surface air temperature (SAT) is 0.3 K colder in the MH, 0.1 K colder at the LIG and unchanged at the MIS 11 time slice. Strongest warming is found above the Arctic Ocean, where the model simulates a mean annual SAT increase by up to 3 K for the MH, up to 7 K for the LIG, and up to 6 K for MIS 11. Applying changes in the vegetation cover, which more realistically represent the biogeography of the interglacial time slices (including expansion of vegetation over North Africa and in the northern hemisphere mid and high latitudes), has crucial impact on the global interglacial climates. Over Siberia, annual mean SAT increases by 2-3 K in all interglacial experiments compared to PI. Globally, the MH becomes 0.4 K warmer, the LIG becomes 0.6 K warmer, and the MIS 11 becomes 0.8 K warmer relative to PI. Polar amplification is much more pronounced after applying the vegetation changes, with an annual mean warming of 5-6 K over the Arctic Ocean at the MH, up to 9 K at the LIG, and 7-8 K at MIS 11. The large polar temperature changes during the LIG are associated with a seasonally ice-free Arctic Ocean. The vegetation changes also impact the interglacial atmospheric water cycles, most pronounced in Northern Hemisphere monsoon regions. In particular, the West African monsoon is substantially amplified in response to the expansion of vegetation. Physical processes causing these changes are analyzed. In summary, the results suggest that the intricate interplay between climate and vegetation stands as one of the fundamental mechanisms shaping the dynamics of past interglacials, which needs to be more carefully addressed in future model studies.

Fixed-point photo monitoring supplemented by animal census data and climate monitoring potential has never been explored as a long-term monitoring tool for studying vegetation change in the arid and semi-arid national parks of South Africa. The long-term (1988–2010), fixed-point monitoring dataset developed for the Camdeboo National Park, therefore, provides an important opportunity to do this. Using a quantitative estimate of the change in vegetation and growth form cover in 1152 fixed-point photographs, as well as series of step-point vegetation surveys at each photo monitoring site, this study documented the extent of vegetation change in the park in response to key climate drivers, such as rainfall, as well as land use drivers such as herbivory by indigenous ungulates. We demonstrated the varied response of vegetation cover within three main growth forms (grasses, dwarf shrubs [< 1 m] and tall shrubs [> 1 m]) in three different vegetation units and landforms (slopes, plains, rivers) within the Camdeboo National Park since 1988. Sites within Albany Thicket and Dwarf Shrublands showed the least change in vegetation cover, whilst Azonal vegetation and Grassy Dwarf Shrublands were more dynamic. Abiotic factors such as drought and flooding, total annual rainfall and rainfall seasonality appeared to have the greatest influence on growth form cover as assessed from the fixed-point photographs. Herbivory appeared not to have had a noticeable impact on the vegetation of the Camdeboo National Park as far as could be determined from the rather coarse approach used in this analysis and herbivore densities remained relatively low over the study duration.Conservation implications: We provided an historical assessment of the pattern of vegetation and climatic trends that can help evaluate many of South African National Parks’ biodiversity monitoring programmes, especially relating to habitat change. It will help arid parks in assessing the trajectories of vegetation in response to herbivory, climate and management interventions.

Fixed-point photo monitoring supplemented by animal census data and climate monitoring potential has never been explored as a long-term monitoring tool for studying vegetation change in the arid and semi-arid national parks of South Africa. The long-term (1988–2010), fixed-point monitoring dataset developed for the Camdeboo National Park, therefore, provides an important opportunity to do this. Using a quantitative estimate of the change in vegetation and growth form cover in 1152 fixed-point photographs, as well as series of step-point vegetation surveys at each photo monitoring site, this study documented the extent of vegetation change in the park in response to key climate drivers, such as rainfall, as well as land use drivers such as herbivory by indigenous ungulates. We demonstrated the varied response of vegetation cover within three main growth forms (grasses, dwarf shrubs [< 1 m] and tall shrubs [> 1 m]) in three different vegetation units and landforms (slopes, plains, rivers) within the Camdeboo National Park since 1988. Sites within Albany Thicket and Dwarf Shrublands showed the least change in vegetation cover, whilst Azonal vegetation and Grassy Dwarf Shrublands were more dynamic. Abiotic factors such as drought and flooding, total annual rainfall and rainfall seasonality appeared to have the greatest influence on growth form cover as assessed from the fixed-point photographs. Herbivory appeared not to have had a noticeable impact on the vegetation of the Camdeboo National Park as far as could be determined from the rather coarse approach used in this analysis and herbivore densities remained relatively low over the study duration.Conservation implications: We provided an historical assessment of the pattern of vegetation and climatic trends that can help evaluate many of South African National Parks’ biodiversity monitoring programmes, especially relating to habitat change. It will help arid parks in assessing the trajectories of vegetation in response to herbivory, climate and management interventions.

Monitoring the changes in island vegetation is crucial to understand the global ecological processes as well as to design effective conservation strategies. Globally, remote sensing has emerged as a powerful technology to assess vegetation change across the landscapes. The present study has mapped and analysed changes in the vegetation of islands of Gulf of Mannar Biosphere Reserve (GMBR), Tamil Nadu. The study utilizes Sentinel-2 data to create accurate and up-to-date vegetation and land cover maps for the islands of GMBR in 2022. Landsat data obtained in 2001, 2005, and 2021 were used to create the spatial database on vegetation changes for the islands through a normalised difference vegetation index. The work presents the salient findings specific to the GMBR, showcasing how the islands within this Biosphere Reserve have experienced changes in their vegetation cover over the studied periods. The vegetation cover experienced a decline between 2001 and 2005. However, the vegetation cover has largely been recovered during the period from 2005 to 2021.

Vegetation cover dynamics on the northeastern Qinghai-Tibet Plateau since late Marine Isotope Stage 3