Dendrochronology of maritime pine in the middle of the Atlantic Ocean

Abstract

The Azores Archipelago, located in the North Atlantic Ridge, experiences heavy rainfall and mild temperatures with weak seasonal differences due to oceanic influence. To our knowledge, there have been no dendrochronological studies in the Azores. The aim of this study is to explore the dendrochronological potential of Pinus pinaster Ait. growing in this archipelago and to determine what limiting factor is regulating tree growth. To do so, we have sampled adult maritime pine trees growing in a plantation, in the Pico island of the Azores. Tree ring boundaries were not always easily distinguished, suggesting that in some years cambial activity did not stop during winter. Despite this, it was possible to successfully crossdate the tree-ring series and to establish a tree-ring width chronology with a strong common signal. Climatic correlations revealed a positive response to spring precipitation but no temperature signal in the tree-ring width chronology. Tree-ring width was also negatively correlated with the North Atlantic Oscillation (NAO) and the sea level pressure (SLP) in May − June. Intra-annual density fluctuations (IADFs), which are anatomical features formed in response to variations in environmental conditions during the growing season, were present in 85% of the tree rings. IADFs were identified based on its position within the ring: type E + , characterized as a transition wood from early-to latewood; type L, the most frequent, characterized as earlywood-like cells within latewood; and type L + , characterized as earlywood-like cells between latewood and earlywood of the next tree ring. Each IADF type presented a unique climatic signal: type E + was positively correlated with early summer precipitation and early spring temperature; type L was positively correlated with early autumn precipitation and temperature; and type L + was positively correlated with late autumn precipitation. In conclusion, the tree-ring width chronology established for maritime pine growing in the Pico Island of Azores contains a clear climatic signal for spring precipitation, whereas IADFs frequency correlated better with precipitation later in the growing season. For this reason, we suggest that IADFs should be included in future dendrochronological studies in the Macaronesia Biogeographical region since they can improve the climatic signal present in tree-ring width chronologies.

Extreme Growth Increments Reveal Local and Regional Climatic Signals in Two Pinus pinaster Populations

“…Convergent growth increment was observed in years with above average previous winter and May precipitation, whereas growth reduction (convergent negative) was observed in years with below average spring precipitation and above average summer temperature. Positive event years were associated with precipitation in previous winter and spring, as previously reported for P. pinaster growing in Portugal (Vieira et al, 2009(Vieira et al, , 2017aCampelo et al, 2013Campelo et al, , 2015, Spain (Arzac et al, 2018;Caminero et al, 2018), and Italy (Mazza et al, 2015). The correlation analysis confirmed the positive signal with previous autumn and winter precipitation in tree-ring width.…”

Climate–Growth Relationships in Laurus azorica—A Dominant Tree in the Azorean Laurel Forest

“…Hence, this work, together with recent studies dealing with other important laurel forest trees [11,43], contributes to building baseline climate-growth relationships in an island forest under low climatic seasonality. Furthermore, future dendrochronological studies could be applied to other relevant native or introduced species (e.g., [10,11]), or to other Macaronesian islands (e.g., [13,[16][17][18][19]34]). Nonetheless, due to the high levels of within-stand variation, and to refine the climate-growth analysis, different approaches and proxies will have to be explored in the future, including early and latewood vessel area [159,160] since most native species are angiosperms.…”

“…In the reduced models, possible precipitation effects were detected only in two cases: August precipitation with a positive effect on MT, and May precipitation with a negative effect on LO. −0.06556 Note: + positive effect, − negative effect; * p = 0.05, ** p = 0.01, *** p = 0.001; T = temperature for different months (1-12); P = precipitation for different months (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12); suffix Pre = previous year temperatures or previous year precipitation.…”

“…Orographic precipitation regimes and complex topography lead to considerable spatial variation in temperature and water availability, facilitating studies of climate-growth relationships across environmental gradients [4][5][6][7], and allowing us to better understand the potential impact of a shifting climate on island species. Nevertheless, wood anatomy and growth dynamics of forest trees in oceanic islands remain largely underexplored [8][9][10][11][12][13][14][15], particularly in Macaronesia [10,11,13,14,[16][17][18][19], a biogeographic region including North Atlantic low risk of cavitation in the Azores, due to high water availability, except during the driest summer months at low-elevation sites.…”

“…Note: + positive effect, − negative effect; T = temperature for different months(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12); P = precipitation for different months(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12); suffix Pre = previous year temperatures or previous year precipitation. CC, model for the composite chronology; GM to NO, models for each individual site chronology.…”