Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest

Abstract

One contribution of 24 to a discussion meeting issue 'The interaction of fire and mankind'. South American seasonally dry tropical forests (SDTFs) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12 000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the Early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8000 and 7000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined but severe regional droughts persisted through the Middle Holocene, SDTFs, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTFs are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime.This article is part of the themed issue 'The interaction of fire and mankind'.

Biogeochemical Responses to Holocene Catchment‐Lake Dynamics in the Tasmanian World Heritage Area, Australia

“…Terrestrial and aquatic ecosystem dynamics are influenced by climatic change (e.g., Ball et al, 2010;Fritz & Anderson, 2013;Massaferro et al, 2013), land-use/vegetation alteration (e.g., Cooper et al, 2015;Kissman et al, 2017), and fire regime shifts (e.g., Araneda et al, 2013;Bixby et al, 2015;Brown et al, 2014) at multiple scales of space and time. Given the importance and the interconnectedness of both climate and fire (e.g., Emelko et al, 2016;Fletcher et al, 2014;Power et al, 2016), and terrestrial and aquatic ecosystems (Beck, Fletcher, Kattel, et al, 2018;Kissman et al, 2017;Strock et al, 2017), the paucity of research on how climate and fire drive terrestrial and aquatic ecosystem dynamics constitutes a critical knowledge gap that potentially undermines effective management and conservation endeavors. This lack of cross-cutting research is particularly salient in Australia, where fires are key ecological agent that both has shaped the unique flora of the region (Bowman, 2000) and threatens relict fire-sensitive plant systems with extinction (Holz et al, 2014).…”

Living on a flammable planet: interdisciplinary, cross-scalar and varied cultural lessons, prospects and challenges

“…These challenges cut across particular geographical, social and temporal scales that require equivalent scientific and policy emphasis. From transnational Earth system impacts [1], to domestic impacts on sovereign nations [2], to impacts on local communities [3] and the individuals who make up communities, the perceptions, decisionmaking and prioritization of policy goals are built upon cultural and historical experiences [4][5][6] that have legacy effects, lags and feedbacks across temporal scales [7][8][9][10][11][12]. Although there is a growing literature on building fire-adapted communities [13,14], it is important to recognize that there is both heterogeneity and variability in the historical, technological, cultural and environmental contexts in which humans perceive and respond to fire challenges [15], and that in turn these have cross-scalar feedbacks through sociopolitical structures [2,16], intergenerational cultural transmission [5], historical ecology of landscapes and biomes [12,17,18], and even fire-atmosphere-climate feedbacks [19][20][21].…”

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

“…Drier climatic conditions may indirectly influence dry forest-savannah ecotones by driving an increase in fire frequency, in turn leading to upland savannah expansion due to the greater fire tolerance/adaptation of upland savannah tree taxa compared with dry forest tree taxa (Pennington et al, 2009). While fire has been shown to be a persistent feature of the Chiquitano dry forest throughout the Holocene (Power et al, 2016), the sensitivity of the Chiquitano dry forest-savannah ecotone to the combination of drought and fire has not been explored. Furthermore, a study by Power et al (2016) suggests that the primary driver of floristic turnover within the Chiquitano dry forest during the Holocene may have been climate, as some taxa are better adapted to water stress than others.…”

“…Therefore, it is possible that drier climatic conditions may cause floristic turnover within the forest, even if full biome turnover is not achieved (i.e., replacement of dry forest by upland savannah). However, because the Power et al (2016) study is based on a single lake sediment core, the broader-scale implications of this study are open to question. More palaeoecological records are needed to better elucidate the long-term, potentially complex interactions among tropical dry forests, climate, fire, and edaphic factors.…”