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Understanding the fire evolution history and its driving mechanisms can provide useful insights into the fire regimes and their potential impacts in the future. Here, we present a well-dated peat profile with high-resolution charcoal and pollen records to reconstruct the fire and vegetation history in the Sanjiang Plain over the last 6000 yr. The regional and local fire frequencies were reconstructed with the microscopic (< 125 μm) and macroscopic (> 125 μm) charcoal fractions, respectively. During the interval ~ 6.0–4.5 ka BP, both the regional and local fires exhibited much low frequencies responding to the strong summer monsoon. Thereafter, the fire frequencies increased significantly with the decline of the summer monsoon, and the highest frequencies corresponded well with the weak monsoon intervals around 4.0, 2.7, and 0.8 ka BP. As for the local fires, in addition to the climate changes, the local vegetation conditions have also served an important role in driving their occurrences. During the last 300 yr, the gradually increased fire frequencies were attributed to the intensified human activities instead of the climate and vegetation influences. [ABSTRACT FROM AUTHOR]

Peatlands contain around one third of the global soil carbon (C) and play an important role in the C cycle. In particular, the response of the productivity-decay balance to climate variability is critical for understanding both the past and future global C cycle. Most studies of peatland C dynamics have been carried out on boreal and subarctic peatlands, where climate models predict a greater increase in temperature compared to the global average. Less is known about peatlands at lower latitudes, yet there are significant peatland C stocks in these regions that may be more vulnerable to future climate change because they are closer to the climatic limit of peatland distribution. Northeast China is China's largest wetland region, with extensive peatlands in mountain regions and across the plains. Here, we used core data from 134 peatland sites to quantify the C accumulation rate over different timescales and estimate C storage across northeast China. The results show that the Holocene long-term apparent rate of C accumulation (LORCA) ranged from 5.74 to 129.31 g C m −2 yr −1 , with a mean rate of 33.66 g C m −2 yr −1 . The total wetland area and C storage within this region is 82,870 km 2 and 4.34 Gt C, and about 80% of the C is contained in mountain peatlands. We find that total C accumulated over the last 2000 years is linearly related to photosynthetically active radiation over the growing season, supporting the hypothesis that rates of net primary productivity (NPP) are more important than decomposition rates in determining long-term C accumulation. Although peatlands in northeast China are close to the southern limit of major peatland extent, our data suggest that future warming will lead to greater future C accumulation, as long as moisture balance or cloudiness do not become limiting factors. [ABSTRACT FROM AUTHOR]