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Ice wear is one of important factors affecting the damage of hydraulic concrete. In order to investigate the wear law of natural pumice concrete under ice friction, natural pumice in Inner Mongolia was used as coarse aggregate, and the effects of volume fraction of pumice aggregate, water-binder ratio and cementitious material hardness on the wear of natural pumice concrete were studied. The significance of different influencing factors on the wear amount of natural pumice concrete was analyzed. The apparent morphology of natural pumice concrete under ice wear was observed by super depth of field microscope. The results show that the wear amount of natural pumice concrete increases with the increase of pumice aggregate volume fraction and water-binder ratio, and decreases with the increase of cementitious material hardness. The volume fraction of pumice aggregate and water-binder ratio have significant effects on the wear amount of natural pumice concrete. The surface material of natural pumice concrete falls off under the action of cutting and fatigue wear mechanisms. The hole wall of the worn surface is damaged and the holes are enlarged. [ABSTRACT FROM AUTHOR]

Fire is one of the most widespread and destructive disasters, which causes property losses, casualties, and disruption of the balance of ecosystems. Therefore, it is highly necessary for firefighting to study the variations in fire and its climatic attributions. This study analyzed the characteristics of fire-burned area (BA) and its response to climatic factors in seven subregions of China from 2001 to 2018 using satellite remote sensing BA products. The results show that the BA in China and most of its subregions shows a decreasing trend. In general, it is negatively correlated with precipitation and positively correlated with air temperature and wind speed based on the regression and correlation analyses. Based on Pearson correlation and random forest methods, it is also found that the temperature is commonly an important factor contributing to BA in China, except for R2 (Inner Mongolia region), where wind speed is more important, and R5 (South China), where precipitation is more important, which coexists at annual and seasonal scales. Besides temperature, precipitation in spring and summer is the main driving factor, such as in R1 (Northeast China), R5, R6 (Northwest China) and R7 (Qinghai–Tibet Plateau) in spring and R4 (Central China), R5 and R7 in summer; and wind speed in autumn and winter is the main driving factor, such as in R2 and R4 in autumn and R2, R3, R5, R6 and R7 in winter. Finally, the distributions of BA with respect to each climatic factor were also analyzed to quantify the range of climatic factors with maximum BA occurrence. [ABSTRACT FROM AUTHOR]

• The >0 °C annual accumulated temperature of Inner Mongolia significantly increased. • The typical steppe has expanded during the past 30 years. • Grassland degradation occurred caused by climate change in Inner Mongolia. As one of the most widespread vegetation types, grasslands play a key role in the terrestrial ecosystem. In China, grasslands are threatened by degradation due to both local human activities and climate change. To analyze the spatiotemporal variation in grassland vegetation under climate change conditions, this study analyzed the climate conditions over the past 30 years in Inner Mongolia, China. The changes in grassland vegetation types over the past 30 years were simulated by the Integrated Orderly Classification System of Grassland (IOCSG), which determined the grassland types by using the >0 °C annual accumulated temperature (AAT0) and moisture index (k-value). To validate the simulated results, the normalized differential vegetation index (NDVI) was used to reflect the real vegetation variations. Over the past 30 years, the AAT0 significantly increased at a rate of 109.8 d °C /decade, and the k-value showed a nonsignificant decrease at the regional scale. The simulated results by the IOCSG showed that the areas of forest and forest steppe and meadow steppe in the past 10 years (2005–2015) decreased by 14.9% and 30.8%, respectively, compared with those in the period from 1986 to 1975. However, the areas of typical steppe and desert and semidesert showed increases of 45.6% and 5.4%, respectively, over the past 10 years compared to those from 1986 to 1975. A typical steppe area of 2.46 × 104 km2 has changed to desert and semidesert, and a meadow steppe area of 10.98 × 104 km2 has changed to typical steppe in the past 30 years. In most regions where the grassland types were predicted to have changed, the annual maximum value of NDVI (amNDVI) showed the same variation trend as the results from the IOCSG. During the study period, the amNDVI significantly decreased in the regions where the vegetation types changed from forest and forest steppe to meadow steppe, while it significantly increased where the vegetation types changed from meadow steppe to forest and forest steppe. However, in some areas, for example, the midland of Ordos, the amNDVI showed the opposite trend with the predicted results, which may have been due to the effects of human activities. Overall, grassland degradation in Inner Mongolia was predicted by the IOCSG, and the results were in accordance with the NDVI variations, which is of great significance for better understanding the grassland conditions under a changing climate. [ABSTRACT FROM AUTHOR]