The Application of Modified Normalized Difference Water Index (MNDWI) by Leaf Area Index in the Retrieval of Regional Drought Monitoring

The vegetation coverage is one of the important factors that restrict the accuracy of remote sensing retrieval of soil moisture. In order to effectively improve the accuracy of the remote sensing retrieval of soil moisture and to reduce the impact of vegetation coverage variation on the retrieval accuracy, the Leaf Area Index (LAI) is introduced to the Normalized Difference Water Index (NDWI) to greatly improve the accuracy of the soil moisture retrieval. In its application on the regional drought monitoring, the paper uses the relative LAI from two places which locate in the north and south of Henan Province respectively (Xin Xiang and Zhu Ma Dian) as indicators. It uses the days after turned-green stage to conduct difference value correction on the Relative Leaf Area Index (RLAL) of the entire province, so as to acquire the distribution of RLAI of the province’s wheat producing area. After this, the local remote sensing NDWI will be Modified （MNDWI = NDWI ×RLAI ） to acquire the soil moisture distribution status of the entire province’s wheat producing area. The result shows that, the Modified Normalized Difference Water Index of LAI which based on the days after turned-green stage can improve the real time retrieval accuracy of soil moisture under different vegetation coverage

Environmental Quality Assessment of Urban Ecology based on Spatial Heterogeneity and Remote Sensing Imagery

The phenomenon of urban ecology is very comprehensive, for example, rapid land-use changes, decrease in vegetation cover, dynamic urban climate, high population density, and lack of urban green space. Temporal resolution and spatial resolution of remote sensing data are fundamental requirements for spatial heterogeneity research. Remote sensing data is very effective and efficient for measuring, mapping, monitoring, and modeling spatial heterogeneity in urban areas. The advantage of remote sensing data is that it can be processed by visual and digital analysis, index transformation, image enhancement, and digital classification. Therefore, various information related to the quality of urban ecology can be processed quickly and accurately. This study integrates urban ecological, environmental data such as vegetation, built-up land, climate, and soil moisture based on spectral image response. The combination of various indices obtained from spatial data, thematic data, and spatial heterogeneity analysis can provide information related to urban ecological status. The results of this study can measure the pressure of environment caused by human activities such as urbanization, vegetation cover and agriculture land decreases, and urban micro-climate phenomenon. Using the same data source indicators, this method is comparable at different spatiotemporal scales and can avoid the variations or errors in weight definitions caused by individual characteristics. Land use changes can be seen from the results of the ecological index. Change is influenced by human behavior in the environment. In 2002, the ecological index illustrated that regions with low ecology still spread. Whereas in 2017, good and bad ecological indices are clustered.     Keywords: spatial heterogeneity, urban ecology, urban remote sensin

Applications of Time-lapse Imagery for Monitoring and Illustrating Ecological Dynamics in a Water-stressed System

Understanding and perceiving the natural world is a key part of management, policy, conservation, and inevitably for our future. Increased demand on natural resources has heightened the importance of documenting ecosystem changes, and knowledge-sharing to foster awareness. The advancement of digital technologies has improved the efficiency of passive monitoring, connectivity among systems, and expanded the potential for innovative and communicative approaches. From technological progression, time-lapse imagery has emerged a valuable tool to capture and depict natural systems. I sought to enhance our understanding of a water-stressed system by analyzing imagery, in addition to integrating images with data visualization to illustrate the complexity of a river basin in central Nebraska. Image analysis was used to quantify wetland water inundation and vegetation phenology. These measurements from visible changes were combined with less visible data from additional passive monitoring to examine the relationship between vegetation phenology and bat activity, as well as wetland inundation and water quality. Moreover, time-lapse data sequences were constructed by integrating time-lapse imagery with data visualization in an interactive digital framework to examine the applications for communicating social-ecological dynamics. Findings suggest vegetation phenology was differentially associated with seasonal bat activity, possibly related to migratory versus resident life history strategies. In regards to examining wetland hydrology, water inundation was found to be correlated with nitrate, dissolved oxygen, and DEA, and negatively correlated with water temperature, indicating the importance of understanding water levels. AEM-RDA analysis identified several significant temporal patterns occurring with the wetland as well as the river site. Similarities between river and wetland patterns were suggestive of regional conditions driving fluctuations, while discrepancies were indicative of structural, biological, and local differences within individual sites. In examining communicative applications, time-lapse data sequences depicted a range of ecological dynamics while linking visible and invisible occurrences. The framework shows potential to offer a tangible context with explanatory content to aid in understanding environmental changes that are often too subtle to see or beyond the temporal scale of unaided human observation. Overall, cumulative findings suggest time-lapse imagery is of dual utility and has high potential for collecting data and illustrating ecological dynamics. Advisor: Craig R. Alle

Applications of Time-lapse Imagery for Monitoring and Illustrating Ecological Dynamics in a Water-stressed System

Understanding and perceiving the natural world is a key part of management, policy, conservation, and inevitably for our future. Increased demand on natural resources has heightened the importance of documenting ecosystem changes, and knowledge-sharing to foster awareness. The advancement of digital technologies has improved the efficiency of passive monitoring, connectivity among systems, and expanded the potential for innovative and communicative approaches. From technological progression, time-lapse imagery has emerged a valuable tool to capture and depict natural systems. I sought to enhance our understanding of a water-stressed system by analyzing imagery, in addition to integrating images with data visualization to illustrate the complexity of a river basin in central Nebraska. Image analysis was used to quantify wetland water inundation and vegetation phenology. These measurements from visible changes were combined with less visible data from additional passive monitoring to examine the relationship between vegetation phenology and bat activity, as well as wetland inundation and water quality. Moreover, time-lapse data sequences were constructed by integrating time-lapse imagery with data visualization in an interactive digital framework to examine the applications for communicating social-ecological dynamics. Findings suggest vegetation phenology was differentially associated with seasonal bat activity, possibly related to migratory versus resident life history strategies. In regards to examining wetland hydrology, water inundation was found to be correlated with nitrate, dissolved oxygen, and DEA, and negatively correlated with water temperature, indicating the importance of understanding water levels. AEM-RDA analysis identified several significant temporal patterns occurring with the wetland as well as the river site. Similarities between river and wetland patterns were suggestive of regional conditions driving fluctuations, while discrepancies were indicative of structural, biological, and local differences within individual sites. In examining communicative applications, time-lapse data sequences depicted a range of ecological dynamics while linking visible and invisible occurrences. The framework shows potential to offer a tangible context with explanatory content to aid in understanding environmental changes that are often too subtle to see or beyond the temporal scale of unaided human observation. Overall, cumulative findings suggest time-lapse imagery is of dual utility and has high potential for collecting data and illustrating ecological dynamics. Advisor: Craig R. Alle

Impact of bioturbation on sediment redistribution in coastal Chile - As estimated by combining remote sensing, machine learning and semi-empirical modelling

The burial activity of terrestrial bioturbators influences the microtopography, surface roughness, and physical properties of the soil. By reworking sediments, bioturbators increase soil permeability and porosity, which has implications for infiltration and erosion rates. The construction of underground tunnels distributes and concentrates nutrients and has a particularly positive effect on carbon storage in the soil. Previous studies have left several research gaps. The studies focused only on the habitat preferences of individual species and did not consider the varying amount of excavated sediment and the building density of individual species. It remains unclear which environmental parameters within the catchment area are primarily associated with the high density and distribution of all existing bioturbator structures. Furthermore, the previous authors did not address the daily sediment excavation dynamics by the animal, whether and how it is related to sediment redistribution driven by catchment-wide precipitation, and how much sediment the bioturbators transport to the surface throughout the year. My dissertation was part of the EarthShape consortium with the overarching research question of how microorganisms, animals, and plants influence the shape and development of the Earth's surface. The study was conducted at four study sites along the Chilean coastal cordillera: arid Pan de Azúcar, semi-arid Santa Gracia, Mediterranean La Campana, and humid Nahuelbuta. The workflow consisted of three work packages with the ultimate goal of determining the catchment-wide effects of bioturbation. Within the first work package, I tested whether the density of burrows and the distribution of structures can be predicted by vegetation patterns calculated from UAV and WorldView-2 data. Then I used the best model for catchment-wide prediction. Within the second work package, I tested whether bioturbator-driven sediment redistribution depends on precipitation-driven sediment redistribution. For this purpose, I deployed several time-of-flight-based cameras to monitor sediment redistribution on the trench surface and around the trench. In the third work package, I integrated bioturbation into a soil erosion model. Then I determined the influence of bioturbators on sediment distribution and the environmental parameters that determine the extent of this influence. My results showed that the distribution of structures created by bioturbating animals depends on vegetation patterns. The density of burrows created by bioturbating animals was best predicted by in-situ measured vegetation cover as well as the diameter and height of shrubs. In the arid and semi-arid zones, cactus height and cover were important predictors, while in the humid zone, tree trunk diameter and cover were selected by the model. However, plant species diversity was important in all climatic zones. When predicting burrow density using UAV images, indices of vegetation heterogeneity were also important. The density of structures increased with shrub, herb, and cactus cover in all climatic zones and decreased with tree canopy cover in the humid climate zone. The density of invertebrate structures was higher in rockier areas with less vegetation at all sites. Finally, a vegetation index describing high leaf area index was an important predictor. The distribution of structures throughout the catchment area was best predicted by the WorldView-2 NIR band and NDVI, as well as individual vegetation land cover classes. Topographic features derived from LiDAR data were not selected as important predictors, except for aspect. Secondly, the results showed that sediment redistribution triggered by bioturbators depends on rainfall-triggered redistribution. Immediately after rainfall events in the Mediterranean climate zone, increased sediment export by the animals was observed: the animals were observed reconstructing their structures after the rains and simultaneously excavating more additional sediment to the surface. In contrast, in the arid climate zone, sediment export was mostly not preceded by rainfall events. The results confirmed that the environment determines the extent of the impact of bioturbation on rainfall-induced sediment redistribution throughout the catchment area. The results showed that the key environmental parameters were elevation, surface roughness, slope, and vegetation cover derived from NDVI. Bioturbation increased sediment erosion in areas where erosion processes dominate (steep slopes, strong gradients, low surface roughness, low vegetation cover), and similarly increased sediment accumulation in areas with natural sediment deposition (high surface roughness, high vegetation cover, low slope). The model output demonstrated that bioturbation intensifies sediment erosion. Bioturbation amplified sediment erosion in all climatic zones except the humid zone. Monitoring the structures showed an increase in erosion of over 300% compared to the areas where the structures were embedded. According to the results of the soil erosion model, bioturbation had the strongest impact on erosion in the Mediterranean zone, followed by the arid and semi-arid zones. The effects of bioturbation were not significant in the humid zone. To assess long-term impacts, bioturbation needs to be integrated into landscape development models. However, these models have assumed a uniform distribution and spatial and temporal effects of bioturbation. My results demonstrated that the effects of bioturbation on sediment redistribution are not temporally and spatially consistent, and the distribution of bioturbation is not uniformly associated with vegetation. To realistically predict the long-term effects of bioturbation, the estimated spatial and temporal variations from this study need to be considered

Remote Sensing in Mangroves

The book highlights recent advancements in the mapping and monitoring of mangrove forests using earth observation satellite data. New and historical satellite data and aerial photographs have been used to map the extent, change and bio-physical parameters, such as phenology and biomass. Research was conducted in different parts of the world. Knowledge and understanding gained from this book can be used for the sustainable management of mangrove forests of the worl

Impact of agricultural land use in Central Asia: a review

International audienceAbstractAgriculture is major sector in the economy of Central Asia. The sustainable use of agricultural land is therefore essential to economic growth, human well-being, social equity, and ecosystem services. However, salinization, erosion, and desertification cause severe land degradation which, in turn, degrade human health and ecosystem services. Here, we review the impact of agricultural land use in the five countries of Central Asia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan, during 2008–2013 in 362 articles. We use the Land Use Functions framework to analyze the type and relative shares of environmental, economic, and social topics related to agricultural land use. Our major findings are (1) research on land use in Central Asia received high levels of international attention and the trend in the number of publications exceeded the global average. (2) The impacts of land use on abiotic environmental resources were the most explored. (3) Little research is available about how agricultural land use affects biotic resources. (4) Relationships between land degradation, e.g., salinization and dust storms, and human health were the least explored. (5) The literature is dominated by indirect methods of data analysis, such as remote sensing and mathematical modeling, and in situ data collection makes up only a small proportion

Hotspots of soil water movement induced by vegetation canopies

Vegetation and soil form a highly interactive system, within which water is one of the most important factors. By the redistribution of precipitation and its separation into interception, throughfall and stemflow, vegetation canopies introduce a strong small-scale heterogeneity to downwards-directed water fluxes in forests. This could importantly affect subsequent hydrological and biogeochemical processes. In my study, I addressed the formation of patterns and hotspots of below-canopy precipitation and their imprint on soil water conditions. In a comprehensive experimental approach, I used a high-resolution statistical design to capture overall patterns, and hotspot locations trees to identify extreme impacts of canopy-induced water flow on soil water and properties. In Chapter 1, I show that soil properties, instead of net precipitation patterns, most prominently shaped spatial patterns of soil water content. Soil properties, yet, showed to be spatially organized due to the position of trees, forming areas of enhanced soil drainage around the trunks. In Chapter2, the effects of tree, neighborhood and stand properties on stemflow were identified using linear mixed effects models. Stand density and species diversity increased stemflow due to high woody surface area. The temporal stability of stemflow variation indicates that vegetational impacts are highly relevant. Chapter 3 assesses the spatial distribution of infiltration from stemflow and throughfall and the impact of hotspots on soil properties. Stemflow infiltration areas proved to be extremely small and infiltration depth high. These hotspots formed distinct soil microsites at the base of trees by accelerating soil formation. Thus, vegetation induces water flow hotspots from the canopy to below the rooting zone. This is likely to influence hydrological responses and the separation of rainfall to plant available water in contrast to deep percolation and groundwater recharge