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Research article - Peer-reviewed, 2022

Long-term frequent fires do not decrease topsoil carbon and nitrogen in an Afromontane grassland

Findlay, Nicola; Manson, Alan; Cromsigt, Joris Pgm; Gordijn, Paul; Nixon, Cathy; Rietkerk, Max; Thibaud, Guy; Wassen, Martin J.; te Beest, Mariska;

Abstract

Fire has been an integral evolutionary force shaping and maintaining grassy biomes, such as the Afromontane grasslands of South Africa. Afromontane grasslands represent a large carbon reservoir, but it is uncertain how fire affects their long-term C storage. We investigated the effect of fire regime on soil organic C and N (SOC; SON) in a long-term (39-year) burning experiment in the Maloti-Drakensberg Park, South Africa. We compared SOC and SON sampled in 2004 and 2019 from six treatments differing in fire frequency (annual, biennial, five-year, infrequent) and season (spring, autumn). Average SOC increased significantly between 2004 and 2019. Average SON increased slightly, resulting in a significant increase in C:N ratio, indicating that soil organic matter is becoming less N-eutrophic. Importantly, burning annually in spring increased SOC and SON. This unexpected response is attributed to the aluandic (acidic, high organic matter) properties of Drakensberg soils. Burning in autumn did not increase SOC and SON. The lowest C stocks were observed in infrequently burnt plots. Average C sequestration across all fire treatments was 0.30 Mg ha(-1) y(-1). The observed increase in SOC under frequent fires is contrary to many findings from other studies in grassy ecosystems and notably driven by fire season.

Keywords

fire regime; montane grassland; soil

Published in

African Journal of Range and Forage Science

2022, volume: 39, number: 1, pages: 44-55
Publisher: TAYLOR AND FRANCIS LTD

Authors' information

Findlay, Nicola
Utrecht University
Manson, Alan
University of Kwazulu Natal
Utrecht University
Nelson Mandela University
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies
Gordijn, Paul
South African Environmental Observation Network (SAEON)
Nixon, Cathy
KwaZulu-Natal Department of Agriculture & Rural Development
Rietkerk, Max
Utrecht University
Thibaud, Guy
KwaZulu-Natal Department of Agriculture & Rural Development
Wassen, Martin J.
Utrecht University
te Beest, Mariska
Nelson Mandela University

UKÄ Subject classification

Ecology

Publication Identifiers

DOI: https://doi.org/10.2989/10220119.2021.2016966

URI (permanent link to this page)

https://res.slu.se/id/publ/116262