Late Holocene transition from natural to anthropogenic forcing of fire regime in Arid Central Asia

Fire activity plays a crucial role in carbon emissions and climate change worldwide. Fragile ecosystems in arid Central Asia (ACA) are sensitively affected by fire activity. However, little is known about the patterns and driving forces of past grassland fires in ACA due to the scarcity of sedimentary records. Here, we analyzed concentration and influx of charcoal from the sediment of Lake Sasikul (Tajikistan), to reconstruct the regional and local fire activities on the Pamir Plateau over the past 2500 years. The regional fire activity reconstructed by micro-charcoals (20-50 μm) presents a long-term increasing trend. Comparisons with paleo-vegetation, paleo-climate, and historical data suggest that the regional fire activity before 1000 cal yr BP mainly responded to climate change, while it was more controlled by human activities after 1000 cal yr BP. In addition, the contribution of vegetation (fuel) conditions to regional fire activity has been relatively weak, except for the past few hundred years. Intriguingly, the local fire activity reconstructed from macro-charcoals (>125 μm) has a different trend from the regional one, with the highest level from 1750 to 600 cal yr BP. It is found that the local fire history could be mainly attributed to natural climate changes throughout the study period, consistent with the fact that there is little human impact near the lake even in the modern times. With current global warming and increasing human activities, fire prevention at various spatio-temporal scales faces greater pressure in arid regions. Therefore, clarifying the relationship between the fire activity, vegetation, climate, and human activities can provide a solid scientific basis for developing future wildfire management policies.