Reply on RC2

Yicheng Shen

doi:10.5194/cp-2021-36-ac3

Abstract

Charcoal accumulated in lake, bog or other anoxic sediments through time has been used to document the geographical patterns in changes in fire regimes. Such reconstructions are useful to explore the impact of climate and vegetation changes on fire during periods when the human influence was less prevalent than today. However, charcoal records only provide semi-quantitative estimates of change in biomass burning. Here we derive quantitative estimates of burnt area from vegetation data in two stages. First, we relate the modern charcoal abundance to burnt area using a conversion factor derived from a generalized linear model of burnt area probability based on eight environmental predictors. Then, we establish the relationship between fossil pollen assemblages and burnt area using Tolerance-weighted Weighted Averaging Partial Least-Squares with sampling frequency correction (fxTWA-PLS). We test this approach using the Iberian Peninsula as a case study because it is a fire-prone region with abundant pollen and charcoal records covering the Holocene. We derive the vegetation-burnt area relationship using the 29 records that have both modern and fossil charcoal and pollen data, and then reconstruct palaeo-burnt area for the 114 records with Holocene pollen records. The pollen data predict charcoal abundances through time relatively well (R2 = 0.47) and the changes in reconstructed burnt area are synchronous with known climate changes through the Holocene. This new method opens up the possibility of reconstructing changes in fire regimes quantitatively from pollen records, which are far more numerous than charcoal records.

Highlights

Such reconstructions are useful to explore the impact of climate and vegetation changes on fire during periods when the human influence was less prevalent than today
We establish the relationship between fossil pollen assemblages and burnt area using Tolerance-weighted Weighted Averaging Partial LeastSquares with sampling frequency correction
We test this approach using the Iberian Peninsula as a case study 25 because it is a fire-prone region with abundant pollen and charcoal records covering the Holocene

Summary

Introduction

Fire is an important element in many ecosystems and in the Earth system (Bowman et al, 2009; Resco de Dios, 2020). It impacts vegetation dynamics, ecosystem functioning and biodiversity (Harrison et al, 2010; Ward et al, 2012; Keywood et al, 2013). Ecosystem functioning and biodiversity (Harrison et al, 2010; Ward et al, 2012; Keywood et al, 2013) It affects climate through vegetation changes and the release of trace gases and aerosols. The occurrence of fire is influenced by climate, vegetation properties and human activities. The relationships between fire, natural factors and human influences are still a matter of debate (e.g. Brotons et al, 2013; Bistinas et al, 2014; Knorr et al, 2014; Andela et al, 2017; Forkel et al, 40 2019a, 2019b)

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