Do Southern Hemisphere tree rings record past volcanic events? A case study from New Zealand

Abstract

Abstract. Much of our knowledge about the impacts of volcanic eruptions on climate comes from proxy records. However, little is known about their impact on the low to mid-latitudes of the Southern Hemisphere. Using superposed epoch analysis, we investigated whether volcanic signals could be identified in annual tree-ring series from eight New Zealand dendrochronological species. We found that most species are reliable recorders of volcanic cooling and that the magnitude and persistence of the post-event response can be broadly linked to plant life history traits. Across species, site-based factors, particularly altitude and exposure to prevailing conditions, are more important determinants of the strength of the volcanic response than species. We then investigated whether chronology selection impacts the magnitude of post-volcanic cooling in tree-ring-based temperature reconstructions by developing two new multispecies reconstructions of New Zealand summer (December–February) temperature with one reconstruction from the pool of all available chronologies, and the other from a selected subset shown to be sensitive to volcanic eruptions. Both reconstructions record temperature anomalies that are remarkably consistent with studies based on instrumental temperature and the ensemble mean response of climate models, demonstrating that New Zealand ring widths are reliable indicators of regional volcanic climate response. However, we also found that volcanic response can be complex, with positive, negative, and neutral responses identified – sometimes within the same species group. Species-wide composites thus tend to underestimate the volcanic response. This has important implications for the development of future tree-ring and multiproxy temperature reconstructions from the Southern Hemisphere.

Forest Resilience in the Himalayas Inferred From Tree Growth After Earthquake Disturbances

“…Here, we used a regional chronology (derived by simple averaging of 46 tree‐ring sites) (Figure S1 in Supporting Information ) as a key response and five major earthquakes were taken as key events (1833, 1905, 1916, 1934, and 1936). The averaged regional chronology is widely used to understand the impacts of extreme events at a regional scale (Cook et al., 2013; Higgins et al., 2022). The relationships between tree‐growth and earthquake events was tested by the random bootstrapped method, where confidence interval was calculated by drawing sets of pseudo‐key years ( n = 10,000 bootstrap samples) over the entire time series (Rao et al., 2019).…”