Satellites have different revisit frequencies (i.e., temporal resolutions), ranging from daily to monthly. The satellite revisit frequencies suitable for accurately monitoring the phenology of ...deciduous broad-leaved forests (DBF) are not well-known. To fill this knowledge gap, this study used MODIS Daily Nadir BRDF-Adjusted images to simulate EVI time series with a wide range of temporal resolutions from daily to 52 days, to investigate the impacts of satellite revisit frequency on monitoring spatial and temporal patterns of spring phenology, i.e., the start of season (SOS), of DBF in North America. Then, these EVI time series were used to extract SOS by two common phenology extraction methods (i.e., relative threshold and curvature methods). Our results reveal that <xref ref-type="disp-formula" rid="deqn1">1 ) low temporal resolutions cannot accurately reconstruct real vegetation growth profile, which generally causes a false early SOS detection, <xref ref-type="disp-formula" rid="deqn2">2 ) the impact of temporal resolutions is nonlinear. The accuracy of SOS detection from data with relatively high frequencies (e.g., 7 days) is only slightly lower than that from daily time series but the accuracy decreases largely with low frequencies, and <xref ref-type="disp-formula" rid="deqn3">3 ) validation with ground observations from PhenoCam Network stations and an experiment using three real satellite datasets (i.e., MODIS, Landsat 8, and Sentinel-2) confirm the findings from our simulation study. This study suggests that satellites with medium temporal resolutions, such as Sentinel-2 and Landsat 8, could extract reliable phenology metrics in non-cloudy regions.
Local climate zones (LCZ) describe urban surface structures, supporting studies of urban heat islands, sustainable urbanization, and energy balance. The existing studies mapped LCZs from satellite ...images using scene-based classification, which trained deep-learning classifiers by labeled image patches, segmented satellite images into patches by sliding windows to match the size of training data, and finally classified the segmented patches to obtain LCZ maps. However, sliding windows are different from the real footprints of LCZs, which leads to large errors in classification. To address this problem, this article proposes a parcel-based method for LCZ classification using Sentinel-2 images, road networks, and elevation data. First, the Sentinel-2 images are segmented by the road network to obtain the land parcels as classification units. Second, each image parcel is standardized to match the training dataset, So2Sat LCZ42. Third, the trained convolutional neural network (CNN) is used to classify the standardized parcels into LCZs. Finally, the building height information derived from elevation data is used to refine the LCZs by a rule-based classifier. The results of the four test sites show that the overall accuracy of our method is 0.75, higher than the sliding-window-based method's accuracy of 0.47. Additional simulation experiments demonstrated that parcels derived from road networks can reduce the mixture effect in image patches, and parcel standardization can ensure the transferability of the CNN model trained by regular image patches. Considering that the road network and elevation data are widely available, the proposed method has the potential of mapping LCZs in large areas.
Fine-resolution satellite imagery is needed for characterizing dry-season phenology in tropical forests since many tropical forests are very spatially heterogeneous due to their diverse species and ...environmental background. However, fine-resolution satellite imagery, such as Landsat, has a 16-day revisit cycle that makes it hard to obtain a high-quality vegetation index time series due to persistent clouds in tropical regions. To solve this challenge, this study explored the feasibility of employing a series of advanced technologies for reconstructing a high-quality Landsat time series from 2005 to 2009 for detecting dry-season phenology in tropical forests; Puerto Rico was selected as a testbed. We combined bidirectional reflectance distribution function (BRDF) correction, cloud and shadow screening, and contaminated pixel interpolation to process the raw Landsat time series and developed a thresholding method to extract 15 phenology metrics. The cloud-masked and gap-filled reconstructed images were tested with simulated clouds. In addition, the derived phenology metrics for grassland and forest in the tropical dry forest zone of Puerto Rico were evaluated with ground observations from PhenoCam data and field plots. Results show that clouds and cloud shadows are more accurately detected than the Landsat cloud quality assessment (QA) band, and that data gaps resulting from those clouds and shadows can be accurately reconstructed (R2 = 0.89). In the tropical dry forest zone, the detected phenology dates (such as greenup, browndown, and dry-season length) generally agree with the PhenoCam observations (R2 = 0.69), and Landsat-based phenology is better than MODIS-based phenology for modeling aboveground biomass and leaf area index collected in field plots (plot size is roughly equivalent to a 3 × 3 Landsat pixels). This study suggests that the Landsat time series can be used to characterize the dry-season phenology of tropical forests after careful processing, which will help to improve our understanding of vegetation–climate interactions at fine scales in tropical forests.
Salmon on the Klamath COLLIN, MELISSA
Humboldt journal of social relations,
06/2019, Letnik:
1, Številka:
41
Journal Article
Recenzirano
Odprti dostop
The Klamath is a diverse bioregion widely known for its abundant population of salmon. It extends through the states of Oregon and California, and has a drainage basin of over 15,000 square miles ...that flows into the Klamath River. The three most prevalent species of salmon in the region (Coho, Steelhead, and Chinook) have all experienced sharp declines in populations since the mid-20th century. This is due to human activity such as commercial fishing, logging, dams, and urban development that has altered the salmon's historic migration. This map aims to visualize the various waterways and water bodies that flow throughout the basin, while showing the current accessible watersheds and the historical watersheds that have been anthropogenically blocked.
The beach and coastal sand dunes comprise a dynamic and fragile ecosystem that provides a bounty of ecological services. These lands provide protection from coastal erosion and sea level rise, and ...are home to a rich biodiversity of plant and animal species in addition to their recreational value. The Humboldt Coastal Nature Center and the surrounding coastal dunes (HCNC) are managed as a land trust by Friends of the Dunes (FOD). FOD prioritize the restoration of dune habitats and encourages public involvement through community supported education and stewardship programs, guided nature tours, and naturalist training programs. The faculty, students, and staff of Humboldt State University regularly collaborate with FOD for research and volunteer programs. For example, mapping of the coastal dune habitats was performed in 2016, 2017 and 2018 by students from the intermediate remote sensing class and produced results addressing research gaps on social trails, dune movement, sea level rise, and invasive species distribution. This paper examines the natural and anthropocentric changes to the dune habitat from a geospatial perspective and identifies the social values of visitors to the dunes using HCNC visitor records. A small Unmanned Aerial Vehicle (sUAV) was used to acquire high-resolution imagery and then an orthomosaic image with 14 cm spatial resolution was created using the Structure from Motion (SfM) technique within the software Agisoft PhotoScan. sUAV imagery and existing maps were used to digitize social trails and distinguish them from official trails. Coastline change and dune movement were determined using UAV imagery, NAIP satellite imagery, and lidar data. Visitor records of the HCNC were analysed using word clouds and line charts. The results showed that many of the social trails emerged from the neighborhoods southeast of the FOD land trust. As an observation, some directional signs for public access trails pointed out from the trail and may have caused confusion to visitors and misguided them into creating social trails. The social trails have disturbed nesting colonies of bees and led to trampling of dune mat habitats and rare plant communities. A word cloud created from visitor logs depicted that visitors had wonderful experiences at the coastal dunes and beach and highly support the conservation efforts underway. In conclusion, we believe these findings can be used as baseline information to help inform management techniques in order to better fit the region of interest and support the mission of the Friends of the Dunes land trust.
Human granulocytic anaplasmosis, a tickborne disease caused by the bacterium Anaplasma phagocytophilum, was first identified during 1994 and is now an emerging public health threat in the United ...States. New York state (NYS) has experienced a recent increase in the incidence of anaplasmosis. We analyzed human case surveillance and tick surveillance data collected by the NYS Department of Health for spatiotemporal patterns of disease emergence. We describe the epidemiology and growing incidence of anaplasmosis cases reported during 2010–2018. Spatial analysis showed an expanding hot spot of anaplasmosis in the Capital Region, where incidence increased >8-fold. The prevalence of A. phagocytophilum increased greatly within tick populations in the Capital Region over the same period, and entomologic risk factors were correlated with disease incidence at a local level. These results indicate that anaplasmosis is rapidly emerging in a geographically focused area of NYS, likely driven by localized changes in exposure risk.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Anaplasmosis, caused by the tickborne bacterium Anaplasma phagocytophilum, is an emerging public health threat in the United States. In the northeastern United States, the blacklegged tick (Ixodes ...scapularis) transmits the human pathogenic genetic variant of A. phagocytophilum (Ap-ha) and a nonpathogenic variant (Ap-V1). New York has recently experienced a rapid and geographically focused increase in cases of anaplasmosis. We analyzed A. phagocytophilum-infected I. scapularis ticks collected across New York during 2008-2020 to differentiate between variants and calculate an entomological risk index (ERI) for each. Ap-ha ERI varied between regions and increased in all regions during the final years of the study. Space-time scan analyses detected expanding clusters of Ap-ha located within documented anaplasmosis hotspots. Ap-ha ERI was more positively correlated with anaplasmosis incidence than non-genotyped A. phagocytophilum ERI. Our findings help elucidate the relationship between the spatial ecology of A. phagocytophilum variants and anaplasmosis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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