TY - JOUR
T1 - Human disturbance drives loss of soil organic matter and changes its stability and sources in mangroves
AU - Santos-Andrade, Mauricio
AU - Hatje, Vanessa
AU - Arias-Ortiz, Ariane
AU - Patire, Vinicius F.
AU - da Silva, Luciana A.
N1 - Funding Information:
This work was supported by FAPESB ( PET0034/2012 ) and CNPq ( 441264/2017–4 ). The authors were sponsored by CAPES (VFP, Finance Code 001 ), CNPq (VH, 302823/2018–0 ), FAPESB (MS-A, 28328/2018–1 ) and by the NOAA C&GC Postdoctoral Fellowship Program administered by UCAR - CPAESS (AA-O, # NA18NWS4620043B ). We thank LABCAT-IQ/UFBA for the DTA analysis, the Fazenda Oruabo - Bahia Pesca that granted access to ponds and mangroves, and all the volunteers that helped with the sample collection.
Publisher Copyright:
© 2021 Elsevier Inc.
PY - 2021/11
Y1 - 2021/11
N2 - Mangrove soils with high organic carbon (Corg) content are likely to contain Corg that is vulnerable to remineralization during land use changes. Mangrove conversion to different land uses might deplete soil Corg stocks causing variable carbon dioxide emissions, but the extent of these emissions and the fraction of soil Corg (i.e., labile or stable/recalcitrant) that is mostly lost is poorly understood. Here, we study mangrove soil Corg degradability and its susceptibility to mineralization after mangrove disturbance. We measured changes in soil properties, organic matter (OM) stability and Corg pools and sources across a mangrove disturbance gradient (i.e., pristine forests, degraded mangroves receiving domestic sewage and shrimp farm effluents, and shrimp ponds). Results showed that the conversion of mangroves to shrimp ponds caused the most severe changes in soil properties, OM and Corg characteristics. Shrimp pond soils contained the lowest OM-Corg pools, consisted mostly of stable OM (i.e., recalcitrant and refractory; 36.0 ± 5.7% of the total OM) and enriched δ13Corg (−22.6 ± 2.7‰). Conversely, control mangrove soils had the largest OM-Corg pools consisting of a large unstable OM fraction (i.e., labile; 46.4 ± 4.2%) and lighter δ13Corg (−26.8 ± 0.4‰) being characteristic of Corg from a mangrove origin. Conversion of mangroves to shrimp ponds and its degradation by shrimp farm and domestic sewage effluents caused a loss of 97%, 61%, and 35% of soil Corg stocks in the upper meter, representing potential emissions of ~1200, 800, and 400 Mg CO2 ha−1, respectively. These losses were explained by enhanced OM mineralization of unstable fractions driven by the loss of the physico-chemical protection provided by fine-grained soils and vegetation cover. The differences in Corg stability among sites can be used to predict potential carbon dioxide produced during mineralization, hence aid at prioritizing areas for conservation, restoration or management.
AB - Mangrove soils with high organic carbon (Corg) content are likely to contain Corg that is vulnerable to remineralization during land use changes. Mangrove conversion to different land uses might deplete soil Corg stocks causing variable carbon dioxide emissions, but the extent of these emissions and the fraction of soil Corg (i.e., labile or stable/recalcitrant) that is mostly lost is poorly understood. Here, we study mangrove soil Corg degradability and its susceptibility to mineralization after mangrove disturbance. We measured changes in soil properties, organic matter (OM) stability and Corg pools and sources across a mangrove disturbance gradient (i.e., pristine forests, degraded mangroves receiving domestic sewage and shrimp farm effluents, and shrimp ponds). Results showed that the conversion of mangroves to shrimp ponds caused the most severe changes in soil properties, OM and Corg characteristics. Shrimp pond soils contained the lowest OM-Corg pools, consisted mostly of stable OM (i.e., recalcitrant and refractory; 36.0 ± 5.7% of the total OM) and enriched δ13Corg (−22.6 ± 2.7‰). Conversely, control mangrove soils had the largest OM-Corg pools consisting of a large unstable OM fraction (i.e., labile; 46.4 ± 4.2%) and lighter δ13Corg (−26.8 ± 0.4‰) being characteristic of Corg from a mangrove origin. Conversion of mangroves to shrimp ponds and its degradation by shrimp farm and domestic sewage effluents caused a loss of 97%, 61%, and 35% of soil Corg stocks in the upper meter, representing potential emissions of ~1200, 800, and 400 Mg CO2 ha−1, respectively. These losses were explained by enhanced OM mineralization of unstable fractions driven by the loss of the physico-chemical protection provided by fine-grained soils and vegetation cover. The differences in Corg stability among sites can be used to predict potential carbon dioxide produced during mineralization, hence aid at prioritizing areas for conservation, restoration or management.
KW - Blue carbon ecosystems
KW - Effluent discharge
KW - Land use change
KW - Organic matter stability
KW - Shrimp ponds
UR - http://www.scopus.com/inward/record.url?scp=85110267217&partnerID=8YFLogxK
U2 - 10.1016/j.envres.2021.111663
DO - 10.1016/j.envres.2021.111663
M3 - Article
C2 - 34256076
AN - SCOPUS:85110267217
SN - 0013-9351
VL - 202
JO - Environmental Research
JF - Environmental Research
M1 - 111663
ER -
