TY - JOUR
T1 - Late Miocene C4 Grassland Fire Feedbacks on the Indian Subcontinent
AU - Karp, Allison T.
AU - Uno, Kevin T.
AU - Polissar, Pratigya J.
AU - Freeman, Katherine H.
N1 - Funding Information:
We thank Sally Archibald and one anonymous reviewer for constructive suggestions that improved this manuscript. We thank Denny Walizer (PSU) and Nicole deRoberts (LDEO) for laboratory support. ATK thanks Sarah Ivory, Elizabeth Hajek, Mark Patzkowsky, and Erica Smithwick for constructive feedback on this manuscript. Funding: We gratefully acknowledge funding for this work provided to ATK from the Pennsylvania State Department of Geosciences though the Paul D. Krynine Scholarship, the Donald B. and Mary E. Tait Scholarship in Microbial Biogeochemistry, and Alley Family Graduate Scholarship in Climate Science. ATK was supported by a National Science Foundation (NSF) Graduate Research Fellowship (Grant No. DGE1255832.)
Funding Information:
We thank Sally Archibald and one anonymous reviewer for constructive suggestions that improved this manuscript. We thank Denny Walizer (PSU) and Nicole deRoberts (LDEO) for laboratory support. ATK thanks Sarah Ivory, Elizabeth Hajek, Mark Patzkowsky, and Erica Smithwick for constructive feedback on this manuscript. Funding: We gratefully acknowledge funding for this work provided to ATK from the Pennsylvania State Department of Geosciences though the Paul D. Krynine Scholarship, the Donald B. and Mary E. Tait Scholarship in Microbial Biogeochemistry, and Alley Family Graduate Scholarship in Climate Science. ATK was supported by a National Science Foundation (NSF) Graduate Research Fellowship (Grant No. DGE1255832.)
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/4
Y1 - 2021/4
N2 - Fire dynamics potentially account for the asynchronous timing of the expansion of C4 grasslands throughout the Mio-Pliocene world. Yet how fire, climate, and ecosystems interacted in different settings remain poorly constrained because it is difficult to quantify fires and fuel source over these timescales. Here, we apply molecular proxies for fire occurrence alongside records of vegetation change and paleohydrology in Bengal Fan sediments (ODP Leg 116) to examine fire feedbacks on the south Asian continent. We employ abundances of polycyclic aromatic hydrocarbons (PAHs) to reconstruct fire occurrence and δ13C measurements of pyrogenic PAHs to constrain fuel source and grassland burning. This combination allowed us to test whether: (1) a fire-seasonality forcing facilitated the expansion of grassland ecosystems and (2) a fire-C4 grass burning feedback maintained these systems. PAHs can be sourced from weathered fossil carbon (i.e., a petrogenic source) and from burned terrestrial biomass (i.e., a pyrogenic source). Alkylated and non-alkylated structure abundance data distinguished pyrogenic from petrogenic sourced samples. A sharp increase in pyrogenic PAHs along with increases in δ2H and δ13C values of plant waxes at 7.4 Ma indicates increased fire coincided with the onset of C4 expansion and hydrologic change in South Asia. The correlated 13C enrichment in PAHs, 13C enrichment in plant waxes, and increased abundances of PAHs suggest burning of C4 grasslands likely maintained open ecosystems. Our results link fire to the initial opening of grassland ecosystems on a subcontinental-scale and support disturbance as a critical mechanism of terrestrial biome transition.
AB - Fire dynamics potentially account for the asynchronous timing of the expansion of C4 grasslands throughout the Mio-Pliocene world. Yet how fire, climate, and ecosystems interacted in different settings remain poorly constrained because it is difficult to quantify fires and fuel source over these timescales. Here, we apply molecular proxies for fire occurrence alongside records of vegetation change and paleohydrology in Bengal Fan sediments (ODP Leg 116) to examine fire feedbacks on the south Asian continent. We employ abundances of polycyclic aromatic hydrocarbons (PAHs) to reconstruct fire occurrence and δ13C measurements of pyrogenic PAHs to constrain fuel source and grassland burning. This combination allowed us to test whether: (1) a fire-seasonality forcing facilitated the expansion of grassland ecosystems and (2) a fire-C4 grass burning feedback maintained these systems. PAHs can be sourced from weathered fossil carbon (i.e., a petrogenic source) and from burned terrestrial biomass (i.e., a pyrogenic source). Alkylated and non-alkylated structure abundance data distinguished pyrogenic from petrogenic sourced samples. A sharp increase in pyrogenic PAHs along with increases in δ2H and δ13C values of plant waxes at 7.4 Ma indicates increased fire coincided with the onset of C4 expansion and hydrologic change in South Asia. The correlated 13C enrichment in PAHs, 13C enrichment in plant waxes, and increased abundances of PAHs suggest burning of C4 grasslands likely maintained open ecosystems. Our results link fire to the initial opening of grassland ecosystems on a subcontinental-scale and support disturbance as a critical mechanism of terrestrial biome transition.
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U2 - 10.1029/2020PA004106
DO - 10.1029/2020PA004106
M3 - Article
AN - SCOPUS:85104944436
SN - 2572-4517
VL - 36
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
IS - 4
M1 - e2020PA004106
ER -