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Black carbon (BC), one of the major components of atmosphere aerosol, could be the second dominant driver of climate change. We reconstructed historical trend of BC fluxes in Sanjiang Plain (Northeast China) through peat record to better understand its long-term trend and relationship of this atmosphere aerosol with intensity of human activities. The BC fluxes in peatland were higher than other sedimentary archives. Although global biomass burning decreased in last 150 years, regional large scale reclaiming caused BC fluxes of the Sanjiang Plain increased dramatically between 1950s' and 1980s', most likely resulting from using fire to clearing dense pastures and forests for reclaiming. The BC fluxes have increased since 1900s with increasing of the population and the area of farmland; the increase trend has been more clearly since 1980s. Based on Generalized additive models (GAM), the proportional influence of regional anthropogenic impacts have increased and became dominant factors on BC deposition.

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Black carbon is produced by incomplete combustion of fossil fuels and biomass. The production of black carbon over the last several centuries has been primarily influenced by human activities. Human exploitation of forest resources, together with increases in regional fire frequency and intensity, can increase regional black carbon emissions and can led more black carbon deposited into natural ecosystem. Here, based on 210Pb age‐depth model, we investigated black carbon deposition over several key periods in the last 150 years in 5 peatlands of the Great Hinggan Mountains (Northeast China), an area that has been exploited by humans without forest protection policies. The results showed that average black carbon deposition fluxes from different peatlands in the Great Hinggan Mountains were 1.1 to 4.8 mg·year−1·cm−2, which were similar to other peatland distribution regions and higher than other ecosystems. Frequent and intense fire events during the exploitation period led to regional peak black carbon deposition before the 1980s. After the 1980s, fire events were controlled, and the government implemented forest protection policies that decreased the trend in regional fire frequency in the Great Hinggan Mountains and markedly decreased black carbon deposition. Fire events controlled by regional human activities are therefore the major factor that influence regional black carbon deposition fluxes, and frequent forest fires could increase black carbon deposition fluxes in surrounding ecosystem.

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Flooding regime changes resulting from natural and human activity have been projected to affect wetland plant community structures and functions. It is therefore important to conduct investigations across a range of flooding gradients to assess the impact of flooding depth on wetland vegetation. We conducted this study to identify the pattern of plant height, species richness and aboveground biomass variation along the flooding gradient in floodplain wetlands located in Northeast China. We found that the response of dominant species height to the flooding gradient depends on specific species, i.e., a quadratic response for Carex lasiocarpa, a negative correlation for Calamagrostis angustifolia, and no response for Carex appendiculata. Species richness showed an intermediate effect along the vegetation zone from marsh to wet meadow while aboveground biomass increased. When the communities were analysed separately, only the water table depth had significant impact on species richness for two Carex communities and no variable for C. angustifolia community, while height of dominant species influenced aboveground biomass. When the three above-mentioned communities were grouped together, variations in species richness were mainly determined by community type, water table depth and community mean height, while variations in aboveground biomass were driven by community type and the height of dominant species. These findings indicate that if habitat drying of these herbaceous wetlands in this region continues, then two Carex marshes would be replaced gradually by C. angustifolia wet meadow in the near future. This will lead to a reduction in biodiversity and an increase in productivity and carbon budget. Meanwhile, functional traits must be considered, and should be a focus of attention in future studies on the species diversity and ecosystem function in this region.

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