Remote sensing

遥感
  • 文章类型: Journal Article
    Satellite-observed land surface phenology (LSP) data have helped us better understand terrestrial ecosystem dynamics at large scales. However, uncertainties remain in comprehending LSP variations in Central Asian drylands. In this article, an LSP dataset covering Central Asia (45-100°E, 33-57°N) is introduced. This LSP dataset was produced based on Moderate Resolution Imaging Spectroradiometer (MODIS) 0.05-degree daily reflectance and land cover data. The phenological dynamics of drylands were tracked using the seasonal profiles of near-infrared reflectance of vegetation (NIRv). NIRv time series processing involved the following steps: identifying low-quality observations, smoothing the NIRv time series, and retrieving LSP metrics. In the smoothing step, a median filter was first applied to reduce spikes, after which the stationary wavelet transform (SWT) was used to smooth the NIRv time series. The SWT was performed using the Biorthogonal 1.1 wavelet at a decomposition level of 5. Seven LSP metrics were provided in this dataset, and they were categorized into the following three groups: (1) timing of key phenological events, (2) NIRv values essential for the detection of the phenological events throughout the growing season, and (3) NIRv value linked to vegetation growth state during the growing season. This LSP dataset is useful for investigating dryland ecosystem dynamics in response to climate variations and human activities across Central Asia.
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  • 文章类型: Journal Article
    The COVID-19 pandemic\'s disruptions to human activities prompted serious environmental changes. Here, we assessed the variations in coastal water quality along the Caspian Sea, with a focus on the Iranian coastline, during the lockdown. Utilizing Chlorophyll-a data from MODIS-AQUA satellite from 2015 to 2023 and Singular Spectrum Analysis for temporal trends, we found a 22% Chlorophyll-a concentration decrease along the coast, from 3.2 to 2.5 mg/m³. Additionally, using a deep learning algorithm known as Long Short-Term Memory Networks, we found that, in the absence of lockdown, the Chlorophyll-a concentration would have been 20% higher during the 2020-2023 period. Furthermore, our spatial analysis revealed that 98% of areas experienced about 18% Chlorophyll-a decline. The identified improvement in coastal water quality presents significant opportunities for policymakers to enact regulations and make local administrative decisions aimed at curbing coastal water pollution, particularly in areas experiencing considerable anthropogenic stress.
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  • 文章类型: Journal Article
    We used UAV-LiDAR technology and other advanced remote sensing techniques to evaluate mangrove rehabilitation projects along the eroding shoreline of the Upper Gulf of Thailand. Our results delineate the necessary biophysical conditions for successfully rehabilitating mangroves, establishing optimal conditions under which mangroves can naturally re-establish and thrive. Furthermore, we investigated the effectiveness of different coastal defense structures in fostering mangrove recolonization. Our analysis shows that nearshore breakwaters markedly outperform submerged breakwaters and bamboo fences, with a success rate of over 65% by significantly reducing wave energy that aids sediment trapping. These findings suggest that refinements in the configuration of coastal structures, including the elevation of breakwater crests and selective deployment of bamboo fences, will enhance mangrove rehabilitation success. These insights affirm the role of UAV-LiDAR surveys for optimizing mangrove restoration initiatives, thereby facilitating sustainable development for coastlines plagued by erosion. The insights gleaned offer a blueprint for bolstering the success rate of mangrove rehabilitation projects, directing them toward sustainable coastal development.
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  • 文章类型: Journal Article
    Kolonnawa沼泽(KM)是科伦坡地区重要的湿地生态系统,提供基本生态系统服务的斯里兰卡,由于不断的开采和开垦,近几十年来发生了重大变化。湿地的价值被决策者忽视,尽管它们对于改善水质至关重要,并为大都市地区的放松和娱乐提供了机会。低估湿地的价值会导致其持续恶化和不可避免的损失。调查湿地的变化可以为决策提供重要信息。本研究旨在监测KM的时空土地覆盖动态,并进行前景预测,因为随着时间的推移,KM的总范围逐渐减少,沼泽面积随时间转化为陆地植被。使用GIS应用程序分析了GoogleEarth(2000年至2021年)和无人机数据(2022年)的集体图像。随后,具有唯一单元格ID的50平方米网格正方形旨在链接土地覆盖图,以进行时空土地覆盖变化分析。然后,我们计算土地覆盖类别:地表水,马什,和50平方米网格单元中每张地图的陆地植被比例。网格方格中土地覆被变化的统计比较表明,每个土地覆被类别随时间变化显著。结果表明,KM沼泽的减少导致土地覆盖变化对湿地退化具有积极意义。因此,应采取干预措施,以恢复和可持续管理知识管理。
    Kolonnawa marsh (KM) is an important wetland ecosystem in Colombo district, Sri Lanka that provides essential ecosystem services, and has undergone significant changes over recent decades due to continuous exploitation and reclamation. The values of wetlands are disregarded by decision-makers, despite the fact that they are crucial for improving the quality of water and offer chances for relaxation and amusement in metropolitan areas. Underestimation of the value of wetlands contributes to their continuing deterioration and inevitable loss. Investigating the changes in wetlands can provide crucial information for decision-making. This study aimed to monitor the spatiotemporal land-cover dynamics of KM with the prospect prediction as reduced total extent of KM gradually with time and marsh area being transformed into terrestrial vegetation with time. The collective images from Google Earth (2000 to 2021) and drone data (2022) were analyzed with the GIS application. Subsequently, 50-m2 grid squares with unique cell IDs are designed to link among land cover maps for spatiotemporal land-cover change analysis. Then, we calculate land cover category: surface water, marsh, and terrestrial vegetation proportions for each map in 50-m2 grid cells. Statistical comparison of the land cover changes in grid square cells shows that each land cover category has significant change with the time. The results showed that the reduction of KM marsh resulting in land cover changes has a positive implication on wetland degradation. Thus, interventions should be made for the restoration and sustainable management of KM.
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  • 文章类型: Journal Article
    自2019年底出现以来,SARS-CoV-2病毒已导致全球健康危机,影响数百万人,重塑全球社会和经济。以高空间分辨率研究SARS-CoV-2扩散及其时空动力学的决定因素对于公共卫生和决策至关重要。
    这项研究分析了2020年3月和2022年4月在沃州进行的194,682个地理参考的SARS-CoV-2RT-PCR测试,瑞士。我们使用空间和时间聚类的度量来表征五个不同的大流行时期,例如逆香农熵,胡佛指数,劳埃德平均拥挤指数,和改进的空时DBSCAN算法。我们评估了人口统计,社会经济,以及在每个时期使用极限梯度提升(XGBoost)和SHapley加法扩张(SHAP)促进集群持久性的环境因素,考虑非线性和空间效应。
    我们的发现揭示了病例的空间和时间聚类的重要变化。值得注意的是,流行程度较低的地区总发作率较高。空气污染成为一个因素,显示出与较高的集群持久性具有一致的正相关关系,通过引入模型和,在较小程度上,对流层NO2估计。因素包括人口密度,测试率,地理坐标,还显示出与更高的集群持久性的重要正相关。社会经济指数对集群持久性没有显著贡献,表明它在观察到的动力学中的作用有限,这值得进一步研究。
    总的来说,集群持久性的决定因素在整个研究期间仍然存在.这些发现强调了有效的空气质量管理策略的必要性,以减轻空气污染对公众健康的不利影响。特别是在呼吸道病毒性疾病如COVID-19的背景下。
    UNASSIGNED: Since its emergence in late 2019, the SARS-CoV-2 virus has led to a global health crisis, affecting millions and reshaping societies and economies worldwide. Investigating the determinants of SARS-CoV-2 diffusion and their spatiotemporal dynamics at high spatial resolution is critical for public health and policymaking.
    UNASSIGNED: This study analyses 194,682 georeferenced SARS-CoV-2 RT-PCR tests from March 2020 and April 2022 in the canton of Vaud, Switzerland. We characterized five distinct pandemic periods using metrics of spatial and temporal clustering like inverse Shannon entropy, the Hoover index, Lloyd\'s index of mean crowding, and the modified space-time DBSCAN algorithm. We assessed the demographic, socioeconomic, and environmental factors contributing to cluster persistence during each period using eXtreme Gradient Boosting (XGBoost) and SHapley Additive exPlanations (SHAP), to consider non-linear and spatial effects.
    UNASSIGNED: Our findings reveal important variations in the spatial and temporal clustering of cases. Notably, areas with flatter epidemics had higher total attack rate. Air pollution emerged as a factor showing a consistent positive association with higher cluster persistence, substantiated by both immission models and, to a lesser extent, tropospheric NO2 estimations. Factors including population density, testing rates, and geographical coordinates, also showed important positive associations with higher cluster persistence. The socioeconomic index showed no significant contribution to cluster persistence, suggesting its limited role in the observed dynamics, which warrants further research.
    UNASSIGNED: Overall, the determinants of cluster persistence remained across the study periods. These findings highlight the need for effective air quality management strategies to mitigate air pollution\'s adverse impacts on public health, particularly in the context of respiratory viral diseases like COVID-19.
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  • 文章类型: Journal Article
    大豆是应对全球粮食不安全的重要作物,在世界各地具有重要的经济意义。除了旨在提高产量的基因改良,大豆种子成分也发生了变化。由于作物生长和发育过程中的条件会影响大豆种子中的养分积累,遥感提供了一个独特的机会来估计站作物的种子性状。捕获影响种子组成的物候发展需要以更高的空间和光谱分辨率进行频繁的卫星观测。这项研究介绍了一种新颖的光谱融合技术,称为基于多头核的光谱融合(MKSF),该技术结合了PlanetScope(PS)的较高空间分辨率和Sentinel2(S2)卫星的光谱带。该研究还着重于使用额外的光谱带和不同的统计机器学习模型来估计种子性状,例如,蛋白质,油,蔗糖,淀粉,灰,纤维,和产量。使用来自不同生长阶段的PS和S2图像对训练MKSF,并预测潜在的VNIR1(705nm),VNIR2(740nm),VNIR3(783nm),SWIR1(1610nm),和来自PS图像的SWIR2(2190nm)带。我们的结果表明,VNIR3预测性能最高,其次是VNIR2,VNIR1,SWIR1和SWIR2。在种子性状中,蔗糖在RFR模型中具有最高的预测性能。最后,特征重要性分析揭示了融合图像中MKSF生成的植被指数的重要性。
    Soybean is an essential crop to fight global food insecurity and is of great economic importance around the world. Along with genetic improvements aimed at boosting yield, soybean seed composition also changed. Since conditions during crop growth and development influences nutrient accumulation in soybean seeds, remote sensing offers a unique opportunity to estimate seed traits from the standing crops. Capturing phenological developments that influence seed composition requires frequent satellite observations at higher spatial and spectral resolutions. This study introduces a novel spectral fusion technique called multiheaded kernel-based spectral fusion (MKSF) that combines the higher spatial resolution of PlanetScope (PS) and spectral bands from Sentinel 2 (S2) satellites. The study also focuses on using the additional spectral bands and different statistical machine learning models to estimate seed traits, e.g., protein, oil, sucrose, starch, ash, fiber, and yield. The MKSF was trained using PS and S2 image pairs from different growth stages and predicted the potential VNIR1 (705 nm), VNIR2 (740 nm), VNIR3 (783 nm), SWIR1 (1610 nm), and SWIR2 (2190 nm) bands from the PS images. Our results indicate that VNIR3 prediction performance was the highest followed by VNIR2, VNIR1, SWIR1, and SWIR2. Among the seed traits, sucrose yielded the highest predictive performance with RFR model. Finally, the feature importance analysis revealed the importance of MKSF-generated vegetation indices from fused images.
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  • 文章类型: Journal Article
    旱地在陆地生态系统中是独一无二的,因为它们有很大一部分初级生产是由殖民地蓝细菌等非维管植物促进的,苔藓,还有地衣,即,生物锈蚀,发生在表层土壤上和表层土壤中。生物锈蚀遍布各大洲,包括南极洲,在变化的悬崖上日益活跃的大陆。这里,我们描述了现场测量和采样,遥感,和建模方法来评估泰勒谷弗莱克塞尔湖盆地生物锈病的生境适宜性,南极洲,这是麦克默多干谷长期生态研究计划的主要地点。适合生物锈蚀发育的土壤通常较湿润,碱性较低,与无植被的土壤相比,盐分较少。使用随机森林模型,我们表明重量含水量,电导率,降雪频率是生物存在和生物量的主要预测因子。最适合生长密集生物锈蚀的区域是与季节性积雪有关的土壤。使用地理空间数据将我们的栖息地适宜性模型推断到整个盆地,预测生物锈蚀存在于2.7×105m2中,含有11-72Mg的地上碳,基于90%的发生概率。我们的研究说明了结合野外和遥感数据对了解生物锈病的分布和生物量的协同作用,该地区碳平衡的基础社区。极端天气事件和该地区不断变化的气候条件,尤其是那些影响积雪和持久性的因素,可能会对McMurdo干谷中生物锈病的未来分布和丰度以及土壤有机碳储量产生重大影响。
    Drylands are unique among terrestrial ecosystems in that they have a significant proportion of primary production facilitated by non-vascular plants such as colonial cyanobacteria, moss, and lichens, i.e., biocrusts, which occur on and in the surface soil. Biocrusts inhabit all continents, including Antarctica, an increasingly dynamic continent on the precipice of change. Here, we describe in-situ field surveying and sampling, remote sensing, and modeling approaches to assess the habitat suitability of biocrusts in the Lake Fryxell basin of Taylor Valley, Antarctica, which is the main site of the McMurdo Dry Valleys Long-Term Ecological Research Program. Soils suitable for the development of biocrusts are typically wetter, less alkaline, and less saline compared to unvegetated soils. Using random forest models, we show that gravimetric water content, electrical conductivity, and snow frequency are the top predictors of biocrust presence and biomass. Areas most suitable for the growth of dense biocrusts are soils associated with seasonal snow patches. Using geospatial data to extrapolate our habitat suitability model to the whole basin predicts that biocrusts are present in 2.7 × 105 m2 and contain 11-72 Mg of aboveground carbon, based on the 90% probability of occurrence. Our study illustrates the synergistic effect of combining field and remote sensing data for understanding the distribution and biomass of biocrusts, a foundational community in the carbon balance of this region. Extreme weather events and changing climate conditions in this region, especially those influencing snow accumulation and persistence, could have significant effects on the future distribution and abundance of biocrusts and therefore soil organic carbon storage in the McMurdo Dry Valleys.
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  • 文章类型: Journal Article
    植被是土地之间的重要纽带,大气,和水,使其变化具有重要意义。然而,现有的研究主要集中在长期植被变化上,忽略植被的年内变化。因此,本研究基于2000年至2022年的增强植被指数(EVI)数据,时间步长为16天,分析中国植被年际变化格局。计算了每个市级行政区的年度平均EVI值,并采用时间序列k均值聚类算法来划分这些区域,探索中国植被年际变化的空间变化。最后,岭回归和随机森林方法被用来评估年内植被变化的驱动因素。结果表明:(1)中国的植被状况表现出明显的夏季高,冬季低的年内变化模式。”,北部地区的变化比南部地区更为明显;(2)年度内植被变化表现出明显的区域差异,中国可以最佳地分为四个不同的集群,与中国的温度和降水区很好地吻合;(3)年内植被变化与露点温度等气象因素显着相关,降水,最高温度,和海平面压力。总之,我们的研究揭示了这些特征,中国植被年际变化的空间格局和驱动力,这有助于解释生态系统的反应机制,为生态学研究以及生态保护和管理策略的制定提供有价值的见解。
    Vegetation is an important link between land, atmosphere, and water, making its changes of great significance. However, existing research has predominantly focused on long-term vegetation changes, neglecting the intra-annual variations of vegetation. Hence, this study is based on the Enhanced Vegetation Index (EVI) data from 2000 to 2022, with a time step of 16 days, to analyze the intra-annual patterns of vegetation changes in China. The average intra-annual EVI values for each municipal-level administrative region were calculated, and the time-series k-means clustering algorithm was employed to divide these regions, exploring the spatial variations in China\'s intra-annual vegetation changes. Finally, the ridge regression and random forest methods were utilized to assess the drivers of intra-annual vegetation changes. The results showed that: (1) China\'s vegetation status exhibits a notable intra-annual variation pattern of \"high in summer and low in winter,\" and the changes are more pronounced in the northern regions than in the southern regions; (2) the intra-annual vegetation changes exhibit remarkable regional disparities, and China can be optimally clustered into four distinct clusters, which align well with China\'s temperature and precipitation zones; and (3) the intra-annual vegetation changes demonstrate significant correlations with meteorological factors such as dew point temperature, precipitation, maximum temperature, and sea-level pressure. In conclusion, our study reveals the characteristics, spatial patterns and driving forces of intra-annual vegetation changes in China, which contribute to explaining ecosystem response mechanisms, providing valuable insights for ecological research and the formulation of ecological conservation and management strategies.
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  • 文章类型: Journal Article
    土地覆盖的变化直接影响生物多样性。这里,我们评估了古巴过去35年的土地覆盖变化,并分析了这种变化如何影响Omphalea植物和Uraniaboisduvalii蛾的分布.我们分析了1985年和2020年古巴群岛的植被覆盖。我们使用GoogleEarthEngine将两个卫星图像成分分为七个覆盖类型:森林和灌木,红树林,没有植被覆盖的土壤,湿地,松树林,农业,和水体。我们考虑了四个不同的土地覆盖变化量化领域:(1)古巴群岛,(2)保护区,(3)Omphalea的潜在分布区域,(4)保护区内植物的潜在分布区域。我们发现“森林和灌木”,这是报道了Omphalea种群的覆盖类型,在过去的35年里,古巴的人口大幅增加,过去,大部分获得的森林和灌木地区都是农业用地。在Omphalea的潜在分布区域观察到相同的模式;而几乎所有的覆盖类型在保护区内大多是稳定的。将农业区转变为森林和灌木可能是古巴生物多样性保护的一个有趣机会。有关森林和灌木收益地区生物多样性组成的其他详细研究将大大有助于我们对此类地区保护价值的理解。
    Changes in land cover directly affect biodiversity. Here, we assessed land-cover change in Cuba in the past 35 years and analyzed how this change may affect the distribution of Omphalea plants and Urania boisduvalii moths. We analyzed the vegetation cover of the Cuban archipelago for 1985 and 2020. We used Google Earth Engine to classify two satellite image compositions into seven cover types: forest and shrubs, mangrove, soil without vegetation cover, wetlands, pine forest, agriculture, and water bodies. We considered four different areas for quantifications of land-cover change: (1) Cuban archipelago, (2) protected areas, (3) areas of potential distribution of Omphalea, and (4) areas of potential distribution of the plant within the protected areas. We found that \"forest and shrubs\", which is cover type in which Omphalea populations have been reported, has increased significantly in Cuba in the past 35 years, and that most of the gained forest and shrub areas were agricultural land in the past. This same pattern was observed in the areas of potential distribution of Omphalea; whereas almost all cover types were mostly stable inside the protected areas. The transformation of agricultural areas into forest and shrubs could represent an interesting opportunity for biodiversity conservation in Cuba. Other detailed studies about biodiversity composition in areas of forest and shrubs gain would greatly benefit our understanding of the value of such areas for conservation.
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  • 文章类型: Journal Article
    研究黄河流域蒙古族地区植被覆盖与地理的关系,有助于优化当地植被恢复策略,实现和谐的人文关系。根据MOD13Q1数据,通过趋势和相关分析,研究了2000-2020年蒙古黄河流域植被覆盖度(FVC)的时空变化。研究结果如下:(1)2000-2020年,黄河流域蒙古族段植被恢复良好,FVC的平均增加为0.001/a,植被分布表现为东南高覆盖率,西北低覆盖率,占总面积的31.19%,植被覆盖率显着增加。(2)各地理因子的解释力存在显著差异。降水,土壤类型,空气温度,土地利用类型和坡度是影响植被覆盖空间分布的主要驱动因子,对于每个因素,其与其他因素相互作用的解释力大于单因素。(3)FVC与温度和降水的相关系数主要为正。FVC的平均值及其变化趋势具有地形和土壤特性的差异,人口密度和土地利用。土地利用转换可以反映人类活动的特点,和积极的影响,如退耕还林还草和未利用土地造林,促进区域植被的显著改善,虽然有负面影响,比如城市扩张,抑制植被的生长。
    Studying the relationships between vegetation cover and geography in the Mongolian region of the Yellow River Basin will help to optimize local vegetation recovery strategies and achieve harmonious human relations. Based on MOD13Q1 data, the spatial and temporal variations in fractional vegetation cover (FVC) in the Mongolian Yellow River Basin during 2000-2020 were investigated via trend and correlative analysis. The results are as follows: (1) From 2000 to 2020, the vegetation cover in the Mongolian section of the Yellow River Basin recovered well, the mean increase in the FVC was 0.001/a, the distribution of vegetation showed high coverage in the southeast and low coverage in the northwest, and 31.19% of the total area showed an extremely significant and significant increase in vegetation cover. (2) The explanatory power of each geographic factor significantly differed. Precipitation, soil type, air temperature, land use type and slope were the main driving factors influencing the spatial distribution of the vegetation cover, and for each factor, the explanatory power of its interaction with other factors was greater than that of the single factor. (3) The correlation coefficients between FVC and temperature and precipitation are mainly positive. The mean value of the FVC and its variation trend are characterized by differences in terrain and soil characteristics, population density and land use. Land use conversion can reflect the characteristics of human activities, and positive effects, such as returning farmland to forest and grassland and afforestation of unused land, promote the significant improvement of regional vegetation, while negative effects, such as urban expansion, inhibit the growth of vegetation.
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