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Reconstructing the history of tree cover and exploring the relationship between forest growth and environmental factors are of great significance for predicting future vegetation changes and guiding ecosystem restoration and protection. On the basis of pollen data of two lake cores and three peat profiles in the central–northern parts of the Daxing'an Mountains and using multiple methods, we quantitatively reconstructed the tree cover of the past 2000 years. We found that the reconstruction results of the different methods are quite similar. Among all these methods, random forest had the highest prediction accuracy for modern pollen samples. Therefore, the random forest reconstruction results can better reflect changes in regional tree cover, which was approximately 38%–42% during 2000–200 Cal yr BP. It then obviously increased from a low value of approximately 40% to a modern level of approximately 45%. The precipitation and carbon dioxide (CO 2) concentration were the main drivers for the tree cover before and after 200 Cal yr BP, respectively. This indicates that environments with elevated CO 2 level in the near future will benefit the growth of vegetation in the central–northern parts of the Daxing'an Mountains. • Tree cover over the past 2000 years was reconstructed using multiple methods. • CO 2 concentration and precipitation were found to influence tree cover change. • Rapid increase in tree cover after 200 Cal yr BP was linked to CO 2 concentration. [ABSTRACT FROM AUTHOR]

• Amino acids functionalized GO nanosheets were mixed with Pebax to fabricate MMMs. • Amine and carboxyl groups intensified facilitated mechanism and solution mechanism. • DFT calculation revealed the interaction between gases molecules and amino acids. • Arg@GO/Pebax (0.4) membrane exhibited high CO 2 /N 2 separation performance. Graphene oxide (GO) nanosheets, as versatile nanofillers, can create two-dimensional passageways in mixed matrixed membranes (MMMs), yet the flexible manipulation of GO nanosheets is hampered by the lack of appropriate chemical functional groups. In this study, we chose amino acids（arginine, histidine and cysteine）to modify GO nanosheets by direct crosslinking and the loading content of amino acids on GO nanosheets was more than 20%. The modified GO nanosheets were then filled into the Pebax matrix to prepare MMMs. The CO 2 separation performance of MMMs with different nanofillers was compared and different amino acids modified GO nanosheets could fortify the solution mechanism for CO 2 in the order of arginine@GO ＞ histidine@GO ＞ cysteine@GO. Density functional theory (DFT) calculations were conducted to further elucidate the interaction mechanism between gases molecules and amino acids. Under dry state, the complexation energy (Ec) between CO 2 and amine groups was similar to the Ec between CO 2 and carboxylic groups in amino acids. In particular, 0.4 wt% arg@GO nanosheets rendered the membranes with promising CO 2 permeance of 169 Barrer and CO 2 /N 2 selectivity of 70, and surpassed the 2008 upper bound. The amino acids modified GO nanosheets may enlighten an alternative way to explore CO 2 transfer mechanism within MMMs and fabricate high separation performance membranes. [ABSTRACT FROM AUTHOR]