Charcoal morphologies and morphometrics of a Eurasian grass-dominated system for robust interpretation of past fuel and fire type

IF 3.9 2区 地球科学 Q1 ECOLOGY
A. Feurdean, R. Vachula, Diana Hanganu, A. Stobbe, Maren Gumnior
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Abstract

Abstract. Recent developments in morphological and morphometric analyses of charcoal particles have improved our ability to discern characteristics of burnt plant fuel and interpret fire-type changes. However, burning experiments linking known plants to these metrics are limited, particularly in open ecosystems. This study presents novel analyses of laboratory-produced charcoal of 22 plant species from the steppe regions of Eurasia (Romania and Russia), along with selected samples from three Holocene charcoal and pollen records from the same areas. We characterise charcoal production, morphologies and morphometrics in these grass-dominated environments, thereby enabling more robust interpretations of fuel sources and fire types for palaeofire research. Our experiments demonstrate that fire temperature can introduce biases in charcoal produced among species. Grass charcoal production was significantly lower and decreased more strongly with fire temperature compared to forbs. This suggests an underrepresentation of terrestrial graminoids in sedimentary charcoal assemblages. Morphometric analyses revealed that graminoid charcoal particles were more elongated (length-to-width ratio L/W=4) and narrower (width-to-length ratio W/L=0.38) than forbs (L/W=3.1 and W/L=0.42, respectively), in agreement with a global compilation for graminoids (L/W=4.3 for grass 5.4 grass and wetland graminoids) and forbs (L/W=2.9). However, overlapping L/W values present a challenge for establishing cut-off values for fuel type identification in charcoal assemblages with mixed fuel sources. Based on our analyses and compiled datasets from experimental burns, L/W values above 3.0 may indicate predominantly herbaceous morphologies in temperate grassland-dominated ecosystems, though values are likely to be higher for grass than forb-dominated grasslands. Notably, terrestrial grasses exhibit shorter aspect ratios (L/W=4.3) than wetland graminoids (L/W=6.4), highlighting that the aspect ratio needs tailoring to the specific environment of its application, i.e. wetland vs. terrestrial ecosystems. The long forms of graminoid charcoal particles also suggest their potential for atmospheric longer-distance transport compared to more spherical particles, meaning they likely provide insights into regional fire history. An important finding is that charcoal of herbaceous plants closely corresponded to the pollen record, highlighting a solid link between the dominant vegetation and fuel burnt in grassland-dominated environments. However, the relationship between woody charcoal and tree pollen may be more complex, as tree pollen can travel atmospherically longer distances compared to woody charcoal. Our results also highlight the complex interplay between local vegetation and charcoal composition with human fire use that needs to be considered when interpreting charcoal morphological records. A critical takeaway from this study is the importance of not assuming the universality of previous research findings and instead employing experimental approaches to characterise charcoal particles in new ecosystems prior to the application of these techniques. Furthermore, this study also highlights recommendations for further research in new geographical areas and proposes methodological adjustments to enhance the usefulness of charcoal analysis in fire research.
欧亚草地为主系统的木炭形态和形态计量学,用于可靠解释过去的燃料和火灾类型
摘要木炭颗粒形态和形态计量分析的最新发展提高了我们辨别燃烧植物燃料特征和解释火灾类型变化的能力。然而,将已知植物与这些指标联系起来的燃烧实验非常有限,尤其是在开放的生态系统中。本研究对来自欧亚草原地区(罗马尼亚和俄罗斯)的 22 种植物的实验室生产的木炭以及来自同一地区的三个全新世木炭和花粉记录的部分样本进行了新颖的分析。我们描述了这些以草为主的环境中的木炭生产、形态和形态计量学特征,从而为古火灾研究提供了更可靠的燃料来源和火灾类型解释。我们的实验证明,火灾温度会导致不同物种产生的木炭出现偏差。与草本植物相比,禾本科植物的木炭产量明显较低,并且随着火灾温度的升高而减少。这表明陆生禾本科植物在沉积木炭组合中的代表性不足。形态分析表明,禾本科木炭颗粒比草本植物(长宽比分别为L/W=3.1和W/L=0.42)更细(长宽比L/W=4)、更窄(长宽比W/L=0.38),这与禾本科(禾本科和湿地禾本科的长宽比分别为4.3和5.4)和草本植物(长宽比L/W=2.9)的全球汇编一致。然而,L/W 值的重叠给确定混合燃料来源木炭组合的燃料类型鉴定临界值带来了挑战。根据我们的分析和实验性燃烧的数据集汇编,L/W 值高于 3.0 可能表明温带草地为主的生态系统中主要是草本形态,尽管草地的 L/W 值可能高于禁草为主的草地。值得注意的是,陆生禾本科植物的长宽比(L/W=4.3)比湿地禾本科植物的长宽比(L/W=6.4)要短,这说明长宽比需要根据具体的应用环境(即湿地与陆生生态系统)进行调整。禾本科木炭颗粒的长形还表明,与球形颗粒相比,禾本科木炭颗粒有可能在大气中进行更长距离的迁移,这意味着禾本科木炭颗粒有可能提供有关区域火灾历史的信息。一个重要的发现是,草本植物的木炭与花粉记录密切相关,这突出表明在以草地为主的环境中,主要植被与燃料燃烧之间存在着牢固的联系。然而,木炭与树木花粉之间的关系可能更为复杂,因为与木炭相比,树木花粉可以在大气中传播更长的距离。我们的研究结果还强调了当地植被和木炭成分与人类用火之间复杂的相互作用,在解释木炭形态记录时需要考虑到这一点。本研究的一个重要启示是,不要假设以前的研究结果具有普遍性,而是要在应用这些技术之前,采用实验方法来描述新生态系统中木炭颗粒的特征。此外,本研究还强调了在新的地理区域开展进一步研究的建议,并提出了方法调整建议,以提高木炭分析在火灾研究中的实用性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Biogeosciences
Biogeosciences 环境科学-地球科学综合
CiteScore
8.60
自引率
8.20%
发文量
258
审稿时长
4.2 months
期刊介绍: Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome.
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