No abstract

Multispectral images accessible free of charge have increased significantly from the acquisitions by the wide-field-of-view (WFV) sensors onboard Gaofen-1/-6 (GF-1/-6), the Operational Land Imager (OLI) onboard Landsat 8 (L8), and the Multi-Spectral Instrument (MSI) onboard Sentinel-2 (S2). These images with medium spatial resolutions are beneficial for land-cover mapping to monitor local to global surface dynamics. Comparative analyses of the four sensors in classification were made under different scenarios with five classifiers, mainly based on the simulated multispectral reflectance from well-processed hyperspectral data. With channel reflectance, differences in classification between the L8 OLI and the S2 MSI were generally dependent on the classifier considered, although the two sensors performed similarly. Meanwhile, without channels over the shortwave infrared region, the GF-1/-6 WFVs showed inferior performances. With channel reflectance, the support vector machine (SVM) with Gaussian kernel generally outperformed other classifiers. With the SVM, on average, the GF-1/-6 WFVs and the L8 OLI had great increases (more than 15%) in overall accuracy relative to using the maximum likelihood classifier (MLC), whereas the overall accuracy improvement was about 13% for the S2 MSI. Both SVM and random forest (RF) had greater overall accuracy, which partially solved the problems of imperfect channel settings. However, under the scenario with a small number of training samples, for the GF-1/-6 WFVs, the MLC showed approximate or even better performance compared to RF. Since several factors possibly influence a classifier’s performance, attention should be paid to a comparison and selection of methods. These findings were based on the simulated multispectral reflectance with focusing on spectral channel (i.e., number of channels, spectral range of the channel, and spectral response function), whereas spatial resolution and radiometric quantization were not considered. Furthermore, a limitation of this paper was largely associated with the limited spatial coverage. More case studies should be carried out with real images over areas with different geographical and environmental backgrounds. To improve the comparability in classification among different sensors, further investigations are definitely required.

Building a harmonious relationship between human society and river ecosystems has attracted much attention from both government officials and the academy community. Based on the perspective of social-ecological systems (SES), taking the Carp Brook (located in northern Fujian Province, China) as an example, the construction and maintenance of a time-honored artificial river ecosystem was investigated, and its ecosystem services were analyzed. Findings show that the Carp Brook was constructed through a series of ecological engineering, including a transformation of the river channel, building a stable habitat, and breeding carps. The carps have been protected effectively by some folk customs, such as village regulations and folk belief. Meanwhile, the water quality has been maintained through some engineering and institutional measures, which were completed by the local government and villagers. Furthermore, some cultural elements with local characteristics have been formed during the long years of coexistence between human society and the Carp Brook. Based on a healthy ecosystem and abundant culture elements, the Carp Brook provided continuous ecosystem services to human society for more than 800 years, including regulation services (e.g., water purification and flood control) and cultural services (e.g., tourism, research and education, inspiration). Major enlightenments from the Carp Brook are: (a) the Chinese traditional view of nature is important for the construction and maintenance of an artificial ecosystem; (b) traditional folk customs have a strong binding force regarding the protection of the ecosystem; and (c) the choice between material and immaterial services should be made carefully.

Abstract. The characters of the residential communities over Tong’an District of Xiamen City in thermal environment as well as in biophysical factors were investigated mainly based on the Lansat-8 OLI/TIRS Collection 2 Level-2 products. Specifically, the surface temperature product was used in measuring thermal environment, and the surface reflectance product was used to derive biophysical factors through the tasseled cap transformation as well as the normalized difference vegetation index (NDVI). Among the four types of residential community, the old community in urban area was generally lower in NDVI and in the Wetness component and therefore had higher surface temperature. Varied relationships of surface temperature with biophysical factors among four types were observed, which also demonstrated seasonal variation. At the same time, the preliminary investigation showed that the residential communities located in rural-urban fringe and a small portion of village communities had confronted with problems in thermal environment as well as in surface biophysical conditions. Furthermore, limitations of this study were discussed, mainly in spatial resolution and temporal representativeness of the Landsat-8 OLI/TIRS data, in biophysical components derived from the multi-spectral reflectance without depicting actual landscape, and in no consideration for the background of individual community. As the whole district covers wide and complex territory along with different local climate types, more investigations in details are required.