Oxygen isotopes in tree rings record variation in precipitation δ¹⁸O and amount effects in the south of Mexico

Abstract

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitation δ18O.

Stable Oxygen and Carbon Isotopic Composition of Rice (Oryza sativa L.) Grains as Recorder of Relative Humidity

“…In the present study, the δ 18 O OM of rice grains sampled from 23 sites located in different climatic zones showed a significant relationship with δ 18 O SW . The observed trend of higher δ 18 O OM values for high δ 18 O SW is in agreement with the observations in previous studies on cellulose in other plants growing under varied field conditions (Brienen et al, ; Muangsong et al, ; Treydte et al, ) and in controlled experiments (Sternberg et al, ). In this study, the δ 18 O SW governed 34.3% of the site‐average δ 18 O OM variation, as assessed by the lmg metric.…”

“…A similar response was also documented in Mimosa sp. growing in a tropical dry deciduous forest environment where a stronger effect of source water δ 18 O on OM was recorded in the samples of the wet season (Brienen et al, ).…”

The Influence of Competing Hydroclimate Processes on Stable Isotope Ratios in Tropical Rainfall

“…Indeed, MF and MTD are common secondary influences on δ 18 O P across the tropical rain belt region, particularly along the perimeters of the ITCZ and in the western Indo‐Pacific warm pool (Figure a). The strong influence of moisture source on tropical δ 18 O P provides a mechanistic origin for the regional amount effect noted in the IPWP (Brienen et al, ; Kurita et al, ; Moerman et al, ; Schumacher et al, ; Schumacher & Houze, , ). The regional amount effect refers to the weak correlation between δ 18 O P and P at the same station, but a stronger correlation with P across a broader region (Aggarwal et al, ; Conroy et al, ; Kurita et al, ; Moerman et al, ; Figure c).…”

Guidelines and considerations for designing field experiments simulating precipitation extremes in forest ecosystems

“…Stem increment data (Tier I) can be scaled to derive cumulative biomass change via allometric equations over longer time periods. Combining tree‐ring measurements with stable carbon and oxygen isotopes of wood can provide more specific information on the underlying physiological mechanisms driving growth trends (Brienen, Hietz, Wanek, & Gloor, ; Voltas, Chambel, Prada, & Ferrio, ). Quantifying nonstructural carbohydrates in twigs, stems, and roots can elucidate plant‐level patterns of C allocation to current versus future growth and maintenance (Dickman, McDowell, Sevanto, Pangle, & Pockman, ; Körner, ).…”