Postglacial fire history and interactions with vegetation and climate in southwestern Yunnan Province of China

Abstract

Abstract.A high-resolution, continuous 18.5 kyr (1 kyr = 1000 cal yr BP) macroscopic charcoal record from Qinghai Lake in southwestern Yunnan Province, China, reveals postglacial fire frequency and variability history. The results show that three periods with high-frequency and high-severity fires occurred during the periods 18.5-15.0, 13.0-11.5, and 4.3-0.8 ka, respectively. This record was compared with major pollen taxa and pollen diversity indices from the same core, and tentatively related to the regional climate proxy records with the aim to separate climate-from human-induced fire activity, and discuss vegetation-fire-climate interactions. The results suggest that fire was mainly controlled by climate before 4.3 ka and by the combined actions of climate and humans after 4.3 ka. Before 4.3 ka, high fire activity corresponded to cold and dry climatic conditions, while warm and humid climatic conditions brought infrequent and weak fires. Fire was an important disturbance factor and played an important role in forest dynamics around the study area. Vegetation responses to fire after 4.3 ka are not consistent with those before 4.3 ka, suggesting that human influence on vegetation and fire regimes may have become more prevalent after 4.3 ka. The comparisons between fire activity and vegetation reveal that evergreen oaks are flammable plants and fire-tolerant taxa. Alnus is a fire-adapted taxon and a nonflammable plant, but density of Alnus forest is a key factor to decide its fire resistance. The forests dominated by Lithocarpus/Castanopsis and/or tropical trees and shrubs are not easy to ignite, but Lithocarpus/Castanopsis and tropical trees and shrubs are fire-sensitive taxa. Fire appears to be unfavourable to plant diversity in the study area.

Combining and competing effects between precipitation and temperature on Holocene fire regime evolution inferred from a sedimentary black carbon record in southwestern China

“…Comparison of fire history recorded in Lake XMLT (A, this study) with that in ISM and EASM regions, including BC record (Zhang et al, 2015, B) and charcoal records (Xiao et al, 2017b, C) from Lake Tengchongqinghai, element carbon record from Lake Daihai (Han et al, 2012, D), and the compiled charcoal index for East Asia (Marlon et al, 2013, E). The blue line in curve A shows the 11-sample running mean.…”

“…The fire frequency derived from the charcoal record in Tengchongqinghai crater lake (Fig. 1B) was relatively low before 7.5 cal ka BP and increased gradually from 7.5 to 3.0 cal ka BP (Xiao et al, 2017b) (Fig. 3C).…”

“…S1). Fire activity, on multi-decadal to centennial timescales, recorded in different archives was also not synchronous (Zhang et al, 2015; Xiao et al, 2017a, 2017b). These discrepancies indicate that there are local and regional differences in the occurrence of fire.…”

“…Nevertheless, Lake XMLT is located in a subtropical region that is unlike both the main Tibetan Plateau and lowland southern China. Temperature changes during the Holocene can result in changes in the proportion of dominant vegetation types but may have very little influence on overall plant productivity (Xiao et al, 2017b). Pollen results from an adjacent area in Xishuangbanna (140 km southeast to Lake XMLT) have also confirmed this inference (Gu et al, 2008).…”

Holocene Grassland Fire Dynamics and Forcing Factors in Continental Interior of China

“…In the monsoon-dominated region of eastern and southern China, there is a relatively large number of Holocene fire records from forest-steppe ecotone and various forest zones (e.g., Huang et al, 2006;Xiao et al, 2017;Xue et al, 2018;Yin et al, 2016). It has been indicated by these previous studies that forest fuel load is mostly sufficient and fire activity is negatively correlated with the intensity of Asian summer monsoon, implying that more fires were inferred during drier/cooler periods with a weaker summer monsoon, whereas less fires were estimated during wetter/warmer periods with a stronger summer monsoon.…”