ABSTRACT
The weathering carbon sink (CS) of rocks has a sensitive response to different influencing factors, and it is important to accurately distinguish this response in the global carbon cycle. However, no quantitative analysis of the response mechanism has been performed. In this study, the CS of the 12 types of terrestrial rocks in China from 2000 to 2014 is estimated using the GEM-CO2 model. The relative contribution rates of climate change and ecological restoration to the CS are quantitatively evaluated using the Lindeman-Merenda-Gold model. Results showed that: (1) The CS of terrestrial rocks in China was 17.69 Tg C yr-1, and the CS flux (CSF) was 2.53 t C km-2 yr-1; mixed sedimentary rocks had the highest CS (6.89 Tg C yr-1), and carbonate rocks had the highest CSF (5.8 t C km-2 yr-1). (2) The average annual CSF slightly decreased at a rate of 5.4 kg C km-2 yr-1; the areas of the CSF that decreased in the south were the areas where water budget decreased significantly, and it was the areas with a reduced water budget and ecological deterioration in the north. (3) The relative contribution rates of water budget and precipitation reached 57% and 35%, respectively; the response of the CSF to temperature was evident in areas with low or decreasing temperatures, and the influence of fractional vegetation cover (FVC) on the CSF in low value area was evident. (4) Mixed sedimentary rocks and carbonate rocks displayed a more evident reduction trend in the CSF than other rocks. This research verified the applicability of the GEM-CO2 model in China and presented a scientific basis for quantitative assessment of the impact of climate change and ecological restoration on the CSF.
ABSTRACT
Land surface temperature (LST) can reflect the land surface water-heat exchange process comprehensively, which is considerably significant to the study of environmental change. However, research about LST in karst mountain areas with complex topography is scarce. Therefore, we retrieved the LST in a karst mountain area from Landsat 8 data and explored its relationships with LUCC and NDVI. The results showed that LST of the study area was noticeably affected by altitude and underlying surface type. In summer, abnormal high-temperature zones were observed in the study area, perhaps due to karst rocky desertification. LSTs among different land use types significantly differed with the highest in construction land and the lowest in woodland. The spatial distributions of NDVI and LST exhibited opposite patterns. Under the spatial combination of different land use types, the LST-NDVI feature space showed an obtuse-angled triangle shape and showed a negative linear correlation after removing water body data. In summary, the LST can be retrieved well by the atmospheric correction model from Landsat 8 data. Moreover, the LST of the karst mountain area is controlled by altitude, underlying surface type and aspect. This study provides a reference for land use planning, ecological environment restoration in karst areas.
