Dendroclimatology of Prosopis nigra in the Espinal woodlands, southeastern South America

This paper evaluates the dendrochronological potential of Prosopis nigra in the subtropical xerophytic forests of northeastern Argentina, an area of the Espinal forest particularly poor in dendrochronological records. Our study is based on tree-ring analyses of 23 cross sections providing a high-quality chronology (Rbar = 0.24 and EPS = 0.92). The mean annual radial increment recorded was 2.38 ± 1.51 mm. The inter-annual variability in the tree rings indicates that water availability from the previous winter to the current summer growing season is the major forcing on tree growth. Above-average rainfall and SPEI from July to February favored radial growth. Our results show for the first time the strong influence of both ENSO 3.4 and subtropical Atlantic SST variations, mediated by changes in local precipitation, on the growth of P. nigra in the Espinal. We concluded that P. nigra has great dendrochronological and dendroclimatological potential, since its rings are visible after careful polishing of the samples, and its inter-annual variations in radial growth are related to regional climate variability. These results can help improve our knowledge of the vulnerability of xerophytic forests to climate change in northeastern Argentina. In addition, this dendroclimatological study provides new proxy climate records for the Pampean grasslands, one of the most important food producing regions in the world.