Contrasting controls on tree ring isotope variation for Amazon floodplain and terra firme trees

Author(s)

Ladvocat Cintra, Bruno Barcante ^[1] ; Gloor, Manuel ^[1] ; Boom, Arnoud ^[2] ; Schongart, Jochen ^[3] ; Locosselli, Giuliano Maselli ^[4] ; Brienen, Roel ^[1]

Affiliation

^[1] Univ Leeds, Sch Geog, Leeds LS2 9JT, Garstang North - England

^[2] Univ Leicester, Sch Geol Geog & Environm, Bennett Bldg, Univ Rd, Leicester LE1 7RH, Leics - England

^[3] Natl Inst Amazon Res, Av Andre Araujo 2-936, BR-69067375 Manaus, Amazonas - Brazil

^[4] Univ Sao Paulo, Ins Biosci, Rua Matao 14, BR-05508090 Butanta, SP - Brazil

• Document type: Journal article
• Source: TREE PHYSIOLOGY; v. 39, n. 5, p. 845-860, MAY 2019.
• Web of Science Citations: 0

Abstract

Isotopes in tropical trees rings can improve our understanding of tree responses to climate. We assessed how climate and growing conditions affect tree-ring oxygen and carbon isotopes (delta O-18(TR) and delta C-13(TR)) in four Amazon trees. We analysed within-ring isotope variation for two terra firme (non-flooded) and two floodplain trees growing at sites with varying seasonality. We find distinct intraannual patterns of delta O-18(TR) and delta C-13(TR) driven mostly by seasonal variation in weather and source water delta O-18. Seasonal variation in isotopes was lowest for the tree growing under the wettest conditions. Tree ring cellulose isotope models based on existing theory reproduced well observed within-ring variation with possible contributions of both stomatal and mesophyll conductance to variation in delta C-13(TR). Climate analysis reveal that terra firme delta O-18(TR) signals were related to basin-wide precipitation, indicating a source water delta O-18 influence, while floodplain trees recorded leaf enrichment effects related to local climate. Thus, intrinsically different processes (source water vs leaf enrichment) affect delta O-18(TR) in the two different species analysed. These differences are likely a result of both species-specific traits and of the contrasting growing conditions in the floodplains and terra firme environments. Simultaneous analysis of delta C-13(TR) and delta O-18(TR) supports this interpretation as it shows strongly similar intra-annual patterns for both isotopes in the floodplain trees arising from a common control by leaf stomatal conductance, while terra firme trees showed less covariation between the two isotopes. Our results are interesting from a plant physiological perspective and have implications for climate reconstructions as trees record intrinsically different processes. (AU)

• FAPESP's process: 15/25511-3 - Climate and pollution reconstruction based on urban tree-rings growth records
• Grantee: Giuliano Maselli Locosselli
• Support Opportunities: Scholarships in Brazil - Post-Doctoral