Contemporary fire regimes of Canadian forests have been well documented based on forest fire records between the late 1950s to 1990s. Due to known limitations of fire datasets, an analysis of changes in fire-regime characteristics could not be easily undertaken. This paper presents fire-regime trends nationally and within two zonation systems, the homogeneous fire-regime zones and ecozones, for two time periods, 1959–2015 and 1980–2015. Nationally, trends in both area burned and number of large fires (≥200 ha) have increased significantly since 1959, which might be due to increases in lightning-caused fires. Human-caused fires, in contrast, have shown a decline. Results suggest that large fires have been getting larger over the last 57 years and that the fire season has been starting approximately one week earlier and ending one week later. At the regional level, trends in fire regimes are variable across the country, with fewer significant trends. Area burned, number of large fires, and lightning-caused fires are increasing in most of western Canada, whereas human-caused fires are either stable or declining throughout the country. Overall, Canadian forests appear to have been engaged in a trajectory towards more active fire regimes over the last half century.

HIGHLIGHTS• Pourbaix diagram of Mn-Zn-H 2 O system was used to analyze the charge-discharge processes of Zn/MnO 2 batteries.• Electrochemical reactions with the participation of various ions inside Zn/MnO 2 batteries were revealed.• A detailed explanation of phase evolution inside Zn/MnO 2 batteries was provided.ABSTRACT Aqueous rechargeable Zn/MnO 2 zinc-ion batteries (ZIBs) are reviving recently due to their low cost, non-toxicity, and natural abundance.However, their energy storage mechanism remains controversial due to their complicated electrochemical reactions. Meanwhile, to achieve satisfactory cyclic stability and rate performance of the Zn/MnO 2 ZIBs, Mn 2+ is introduced in the electrolyte (e.g., ZnSO 4 solution), which leads to more complicated reactions inside the ZIBs systems. Herein, based on comprehensive analysis methods including electrochemical analysis and Pourbaix diagram, we provide novel insights into the energy storage mechanism of Zn/MnO 2 batteries in the presence of Mn 2+ . A complex series of electrochemical reactions with the coparticipation of Zn 2+ , H + , Mn 2+ , SO 4 2− , and OH − were revealed. During the first discharge process, co-insertion of Zn 2+ and H + promotes the transformation of MnO 2 into Zn x MnO 4 , MnOOH, and Mn 2 O 3 , accompanying with increased electrolyte pH and the formation of ZnSO 4 ·3Zn(OH) 2 ·5H 2 O. During the subsequent charge process, Zn x MnO 4 , MnOOH, and Mn 2 O 3 revert to α-MnO 2 with the extraction of Zn 2+ and H + , while ZnSO 4 ·3Zn(OH) 2 ·5H 2 O reacts with Mn 2+ to form ZnMn 3 O 7 ·3H 2 O. In the following charge/discharge processes, besides aforementioned electrochemical reactions, Zn 2+ reversibly insert into/extract from α-MnO 2 , Zn x MnO 4 , and ZnMn 3 O 7 ·3H 2 O hosts; ZnSO 4 ·3Zn(OH) 2 ·5H 2 O, Zn 2 Mn 3 O 8 , and ZnMn 2 O 4 convert mutually with the participation of Mn 2+ . This work is believed to provide theoretical guidance for further research on high-performance ZIBs.

HIGHLIGHTS • Various MOF materials were synthesized and investigated as ZIB cathodes. • A long-term stable ZIF-8@Zn anode was proposed by coating ZIF-8 material on the surface of zinc foils. • High-performance aqueous ZIBs were constructed using the Mn(BTC) cathode and the ZIF-8@Zn anode.