Research on mountain ecosystem services (MES) under the influence of climate change and human activities has gradually become the focus of academic attention in recent years. Here, this study analyzes the research hotspots and frontiers of this field based on metrics including main research forces, core journals and papers, research hotspots and topics by using the methods of bibliometrics and text mining. The results revealed the following: (1) the number of papers is increasing rapidly in recent years. From 2015 to 2019, 929 papers were published, with an average of 185 papers per year. But the average cited times of those papers is declining, dropped from 6.01 in 2016 to 4.2 in 2019. The USA, UK, and China rank the top three of the number of papers. Univ Maryland, Univ Oxford and Univ Wisconsin have the greatest influence, with an average of more than 77 citations per paper; (2) The most cited journals are PNAS, WETLANDS, ECOLOGY, AND SOCIETY, which are cited 191.54, 53.91, and 40.00 respectively. Most papers were published in OA journals including SUSTAINABILITY, WATER, Forests since 2017. Ten core papers undertaking knowledge transfer in this field have been identified; (3) analysis of the keywords found a new trend of integration of natural science and humanities. In two development stages of 2000-2014 and 2015-2019, the research hotspots mainly focused on mountain water resources, forest resources, land resources and the impact of climate change and human activities, and there are obvious differences and characteristics in different stages. The hotspot worthy of attention in the near future is the assessment of mountain ecosystem services capacity and value. This is the first comprehensive visualization and analysis of the research hotspots and trends of mountain ecosystem services.

Black Carbon (BC) has been widely recognized as the second largest source of territorial and global climate change as well as a threat to human health. There has been serious concern of BC emission and its impact in Indo-Gangetic Plains (IGP) due to the use of biomass and fossil fuels for cooking, transportation and industrial activities. An attempt has been made to study indoor (Liquefied Petroleum Gas-LPG & Traditional cookstoves users households) and outdoor concentrations; seasonal characteristics; radiative forcing and source of apportionment of BC in three districts (Sitapur, Patna and Murshidabad) of IGP during January to December 2016. The seasonal concentrations of BC in LPG (traditional cookstoves) users households were 3.79 +/- 0.77 mu gm(-3) (25.36 +/- 5.01 mu gm(-3)) during the winter; 2.62 +/- 0.60 mu gm(-3) (16.36 +/- 3.68 mu gm(-3)) during the pre-monsoon; 2.02 +/- 0.355 mu gm(-3) (8.92 +/- 1.98 mu gm(-3)) during the monsoon and 2.19 +/- 0.47 mu gm(-3) (15.17 +/- 3.31 mu gm(-3)) during the post-monsoon seasons. However, the outdoor BC concentrations were 24.20 +/- 4.46, 19.80 +/- 4.34, 8.87 +/- 1.83, and 9.14 +/- 1.84 mu gm(-3) during winter, pre-monsoon, monsoon and post-monsoon seasons respectively. The negative radiative forcing (RF) at the surface suggests a cooling effect while a warming effect appears to be occurring at the top of the atmosphere. The atmospheric forcing of BC and aerosols also show a net warming effect in the selected study areas. The analysis of BC concentrations and fire episodes indicated that the emissions from biomass burning increases the pollution concentration. The backward trajectory analysis through the HYSPLIT model also suggests an additional source of pollutants during winter and pre-monsoon seasons from the northwest and northern region in the IGP.

Understanding how land surfaces respond to climate change requires knowledge of land-surface processes, which control the degree to which interannual variability and mean trends in climatic variables affect the surface energy budget. We use the latest version of the Community Land Model version 3.5 (CLM3.5), which is driven by the latest updated hybrid reanalysis-observation atmospheric forcing dataset constructed by Princeton University, to obtain global distributions of the surface energy budget from 1948 to 2000. We identify climate change hotspots and surface energy flux hotspots from 1948 to 2000. Surface energy flux hotspots, which reflect regions with strong changes in surface energy fluxes, reveal seasonal variations with strong signals in winter, spring, and autumn and weak ones in summer. Locations for surface energy flux hotspots are not, however, fully linked with those for climate change hotspots, suggesting that only in some regions are land surfaces more responsive to climate change in terms of interannual variability and mean trends.