Mapping crop phenology using NDVI time-series derived from HJ-1 A/B data

With the availability of high frequent satellite data, crop phenology could be accurately mapped using time-series remote sensing data. Vegetation index time-series data derived from AVHRR, MODIS, and SPOT-VEGETATION images usually have coarse spatial resolution. Mapping crop phenology parameters using higher spatial resolution images (e.g., Landsat TM-like) is unprecedented. Recently launched HJ-1 A/B CCD sensors boarded on China Environment Satellite provided a feasible and ideal data source for the construction of high spatio-temporal resolution vegetation index time-series. This paper presented a comprehensive method to construct NDVI time-series dataset derived from HJ-1 A/B CCD and demonstrated its application in cropland areas. The procedures of time-series data construction included image preprocessing, signal filtering, and interpolation for daily NDVI images then the NDVI time-series could present a smooth and complete phenological cycle. To demonstrate its application, TIMESAT program was employed to extract phenology parameters of crop lands located in Guanzhong Plain, China. The small-scale test showed that the crop season start/end derived from HJ-1 A/B NDVI time-series was comparable with local agro-metrological observation. The methodology for reconstructing time-series remote sensing data had been proved feasible, though forgoing researches will improve this a lot in mapping crop phenology. Last but not least, further studies should be focused on field-data collection, smoothing method and phenology definitions using time-series remote sensing data

Analysis of the relationship between land surface temperature and wildfire severity in a series of landsat images

The paper assesses spatio-temporal patterns of land surface temperature (LST) and fire severity in the Las Hurdes wildfire of Pinus pinaster forest, which occurred in July 2009, in Extremadura (Spain), from a time series of fifteen Landsat 5 TM images corresponding to 27 post-fire months. The differenced Normalized Burn Ratio (dNBR) was used to evaluate burn severity. The mono-window algorithm was applied to estimate LST from the Landsat thermal band. The burned zones underwent a significant increase in LST after fire. Statistically significant differences have been detected between the LST within regions of burn severity categories. More substantial changes in LST are observed in zones of greater fire severity, which can be explained by the lower emissivity of combustion products found in the burned area and changes in the energy balance related to vegetation removal. As time progresses over the 27 months after fire, LST differences decrease due to vegetation regeneration. The differences in LST and Normalized Difference Vegetation Index (NDVI) values between burn severity categories in each image are highly correlated (r = 0.84). Spatial patterns of severity and post-fire LST obtained from Landsat time series enable an evaluation of the relationship between these variables to predict the natural dynamics of burned areas

The Fire in the Mediterranean Region: A Case Study of Forest Fires in Portugal

Forest fires are a common disturbance in many forest systems in the world and in particular in the Mediterranean region. Their origins can be either natural or anthropogenic. The effects in regard to the time trends, vegetation, and soil will be reflected in the species distribution, forest composition, and soil potential productivity. In general, it can be said that the larger the fire and the shorter the time between two consecutive occurrences, the higher the probability to originate shifts in vegetation and soil degradation. In the Mediterranean region, the number of fire ignitions does not reflect the burnt area due to the occurrence of very large fires. The latter occur in a very small proportion of the number of ignitions, but result in very large burnt areas. Also there seems to be an increasing trend toward larger fires in the Mediterranean region due mainly to climatic and land use changes. This case study highlights the importance of vegetation regrowth a short time after the fire to maintain both forest systems and soil conservation

Utilization of Landsat Imagery to Assess the Impacts of Oil and Gas Extraction on the Tazovsky Peninsula, Siberia

Climatic warming of the Arctic is leading to landscape change through cascading biophysical feedbacks; development, such as oil and gas exploration and extraction, can accelerate or worsen these impacts. Due to restricted access to oil and natural gas fields, in situ environmental impact studies are only allowed in some regions. Satellite imagery analysis provides a mean for assessing impacts in areas with limited access. The Yamburg oil and gas field in western Siberia serves as a case study to assess the effects of infrastructure on an Arctic landscape. This project quantifies the land-cover disturbance that occurred during the development and expansion of the Yamburg field. Google’s recently developed, cloud-based image processing platform, Google Earth Engine, was used in conjunction with traditional Geographic Information System (GIS) analysis to detect, map, and quantify the impacts of infrastructure on the Tazovsky Peninsula between 1983 and 2016, utilizing imagery from the Landsat 4, 5, and 8 satellites. Landscape fragmentation metrics, the Normalized Difference Vegetation Index (NDVI), and change analysis quantified the impacts of extraction infrastructure on the surrounding landscape. As distance from the infrastructure and time since field establishment increased, the associated impacts decreased

Lahars and Lyrics: Learning from Adjustments in Landscape and Culture Following prolonged Volcanic Disturbance on the Island of Montserrat

Explosive volcanic eruptions can profoundly disturb surrounding landscapes. Volcanic phenomena (e.g., pyroclastic density currents, tephra fallout) inundate the headwaters of proximal river systems with vast quantities of sediment. This perturbs the hydrology of these systems which then respond by increasing sediment and water flux to downstream reaches via lahars. These hazardous sediment-laden flows can induce dramatic, potentially destructive, and long-lived geomorphic changes within affected drainages. Most understanding of the readjustment of rivers following volcanic disturbances comes from studies following short-lived, transient eruptions. By contrast, limited research has considered responses to prolonged episodic eruptions, characterised by repeat phases of eruption and quiescence. This thesis addresses this research gap by exploring how the morphodynamics and lahar activity within the Belham Valley, Montserrat, have evolved in response to episodic disturbance by the eruption of Soufriere Hills Volcano, 1995 - present. Methods involved include novel longitudinal synthesis of a range of observational data, from ground-based photographic surveys to satellite-derived Digital Surface Models, as well as statistical analysis, and numerical modelling. I show: 1) episodic eruptions induce distinct fluvial responses, manifesting in aggradation-degradation cycles driven by evolving sediment availability, water supply, and vegetation cover; 2) lahar hazard is mediated by evolving catchment-scale conditions; 3) modelling the temporal evolution of lahar activity in such systems shows promise but remains a challenge. During a research assistantship alongside my PhD, I was heavily involved in the development of a co-created public engagement project on Montserrat, Mountain Aglow. This project sought to incorporate the lived experience of eruption in the form of arts – i.e., lyrics – into Disaster Risk Management (DRM) strategies. The final chapter of this thesis presents an evaluative study of this project. I demonstrate that incorporation of lived experience and co-creation of DRM practices is an effective and recommendable means of improving engagement with at-risk populations