Age-related response of forest floor biogenic volatile organic compound fluxes to boreal forest succession after wildfires

Huizhong Zhang-Turpeinen,Minna Kivimäenpää,Frank Berninger,Kajar Köster,Peng Zhao,Xuan Zhou,Jukka Pumpanen

doi:10.1016/j.agrformet.2021.108584

Abstract

The amplification of global warming in the Northern regions results in a higher probability of wildfires in boreal forests. On the forest floor, wildfires have long-term effects on vegetation composition as well as soil and its microbial communities. A large variety of biogenic volatile organic compounds (BVOCs) such as isoprene, monoterpenes, sesquiterpenes have been observed to be emitted from soil and understory vegetation of boreal forest floor. Ultimately, the fire-induced changes in the forest floor affect its BVOC fluxes, and the recovery of the forest floor determines the quantity and quality of BVOC fluxes. However, the effects of wildfires on forest floor BVOC fluxes are rarely studied. Here we conducted a study of the impacts of post-fire succession on forest floor BVOC fluxes along a 158-year fire chronosequence in boreal Scots pine stands near the northern timberline in north-eastern Finland throughout a growing season. We determined the forest floor BVOC fluxes and investigated how the environmental and ground vegetation characteristics, soil respiration rates, and soil microbial and fungal biomass are associated with the BVOC fluxes during the post-fire succession. The forest floor was a source of diverse BVOCs. Monoterpenes (MTs) were the largest group of emitted BVOCs. We observed forest age-related differences in the forest floor BVOC fluxes along the fire chronosequence. The forest floor BVOC fluxes decreased with the reduction in ground vegetation coverage resulted from wildfire, and the decreased fluxes were also connected to a decrease in microbial activity as a result of the loss of plant roots and soil organic matter. The increase in BVOC fluxes was associated with the recovery of aboveground plant coverage and soils. Our results suggested taking into consideration the implications of BVOC flux variations on the atmospheric chemistry and climate feedbacks.

Highlights

Boreal forest ecosystems are the second largest forest area after tropical forest ecosystems, with about 12.1 × 106 km2 (Potter et al, 1996)
We investigated how the environmental and ground vegetation character istics, soil respiration rates, and soil microbial and fungal biomass are associated with biogenic volatile organic compounds (BVOCs) fluxes
Our study conducted with field observations and focusing on long-term effects of wildfire provided evidence on the age-related differences in forest floor BVOC fluxes along forest succes sion

Summary

Introduction

Boreal forest ecosystems are the second largest forest area after tropical forest ecosystems, with about 12.1 × 106 km (Potter et al, 1996). The forest area in Finland covers about 0.203 × 106 km (Vaahtera et al, 2018). Forest fire is one of the principal natural disturbances affecting forest dynamics and biodiversity, and terrestrial carbon stocks in boreal forest ecosystems (Kelly et al, 2013; Seidl et al, 2017). Boreal forests have a higher risk of fires in the future due to global warming (Moritz et al, 2012) that will be strongest in the higher lati tudes (Collins et al, 2013). An increasing frequency of warm and dry periods is facilitating fire activity in boreal forests (e.g. Kelly et al, 2013; Seidl et al, 2017). The danger of forest fires will most likely increase in Finland, too (Lehtonen et al, 2016)

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