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

Abstract

Tree rings are valuable proxies of past climate that allow inferring past growth responses to climate variability and extreme events, which is only possible considering that the relationship between tree growth and environmental conditions is linear and stable over time. However, in the last decades, divergent growth patterns have been observed in trees from the same forest stand, while unprecedented growth convergence was observed between trees from distant locations. Here, we use a new approach that considers convergent and divergent event years in two populations of Pinus pinaster Aiton in an altitudinal and oceanic-continental gradient to investigate what is triggering divergence and convergence in tree growth. The two study sites are Tocha (TCH), a plantation on sand dunes at low altitude near the ocean, and Serra da Estrela (SdE), a mountain plantation located at 1,100 m altitude, 100 km away from the ocean. The analysis of the climatic conditions in convergent growth years revealed that positive convergent growth was related to above average precipitation in previous winter and that negative convergent growth was related to below average precipitation during the growing season. Divergent growth revealed a temperature signal with warmer temperatures in spring promoting growth in SdE and growth reduction in TCH. Convergent growth was associated with a regional climatic signal, reinforcing the importance of precipitation in the Mediterranean region, and divergent growth to site conditions, revealing local adaptation. The information gathered in this study gives valuable insights on the response of P. pinaster to extreme climatic events, allowing for more adjusted management strategies of Mediterranean pine forests.

Tree-Ring-Based Drought Reconstruction in Northern North China over the Past Century

“…The multiscalar SPEI could represent the different effects of water availability on tree growth in particular periods/seasons in tree-ring analyses and might cause different responses during drought reconstructions. It is important to choose the appropriate SPEI timescales [38,39]. To identify the major environmental signals that influence tree growth, the SPEI at the 1-month scale was used to estimate additional variations in drought.…”

Dendroclimatic Reconstruction of Mean Annual Temperatures over Treeline Regions of Northern Bhutan Himalayas

“…As mentioned earlier, a higher rate of change could take place at altitudes far higher than the meteorological stations, but the divergence could also be compounded by a prolongation of the growing season [96]. The earlier warming of spring can trigger an earlier start of cambial activity and support wider tree-ring widths [96]. The remoteness of the sampled areas likely precludes substantial anthropogenic disturbances, which could also foster increased growth rates not explained by temperatures alone.…”

“…Contrastingly, the divergence problem in this study differs from high latitudes of the North, with decreasing observed temperature and rising NB-TEMR values after 2010 (Figure 7). As mentioned earlier, a higher rate of change could take place at altitudes far higher than the meteorological stations, but the divergence could also be compounded by a prolongation of the growing season [96]. The earlier warming of spring can trigger an earlier start of cambial activity and support wider tree-ring widths [96].…”

Effect of Tree Size Heterogeneity on the Overall Growth Trend of Trees in Coniferous Forests of the Tibetan Plateau

“…Concurrently, forest growth or development can also spontaneously reduce tree size heterogeneity. At lower elevations, increased precipitation can promote radial growth by reducing water stress and accelerating xylem activity during the growing season (Vieira et al 2021). This boost will be more pronounced for smaller trees that grow faster, thus reducing CVR.…”