ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University, PO Box 6811, Cairns, QLD, 4870, Australia.
College of Science and Engineering, James Cook University, PO Box 6811, Cairns, QLD, 4870, Australia.
Sci Rep. 2021 Nov 30;11(1):23157. doi: 10.1038/s41598-021-02618-z.
Fire is an essential component of tropical savannas, driving key ecological feedbacks and functions. Indigenous manipulation of fire has been practiced for tens of millennia in Australian savannas, and there is a renewed interest in understanding the effects of anthropogenic burning on savanna systems. However, separating the impacts of natural and human fire regimes on millennial timescales remains difficult. Here we show using palynological and isotope geochemical proxy records from a rare permanent water body in Northern Australia that vegetation, climate, and fire dynamics were intimately linked over the early to mid-Holocene. As the El Niño/Southern Oscillation (ENSO) intensified during the late Holocene, a decoupling occurred between fire intensity and frequency, landscape vegetation, and the source of vegetation burnt. We infer from this decoupling, that indigenous fire management began or intensified at around 3 cal kyr BP, possibly as a response to ENSO related climate variability. Indigenous fire management reduced fire intensity and targeted understory tropical grasses, enabling woody thickening to continue in a drying climate.
火是热带稀树草原的一个基本组成部分，驱动着关键的生态反馈和功能。在澳大利亚稀树草原，原住民对火的人为操控已经实行了数千年，人们对理解人为燃烧对稀树草原系统的影响重新产生了兴趣。然而，要在千年时间尺度上区分自然和人为火灾的影响仍然很困难。在这里，我们使用来自澳大利亚北部一个罕见的永久性水体的孢粉学和同位素地球化学示踪记录表明，在全新世早期到中期，植被、气候和火灾动态是紧密联系的。随着全新世晚期厄尔尼诺/南方涛动（ENSO）的加剧，火灾强度和频率、景观植被以及燃烧植被的来源之间发生了解耦。我们推断，这种解耦可能是对 ENSO 相关气候变化的反应，表明原住民的火灾管理在大约 3 个 cal 千年前开始或加强。原住民的火灾管理降低了火灾强度，并针对林下热带草，使树木在干燥的气候中继续变厚。
