Urrutia-Jalabert Rocío, Barichivich Jonathan, Szejner Paul, Rozas Vicente, Lara Antonio
Departamento de Ciencias Naturales y Tecnología, Universidad de Aysén, Coyhaique, Chile.
Laboratorio de Dendrocronología y Cambio Global, Instituto de Conservación, Biodiversidad y Territorio, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Valdivia, Chile.
J Geophys Res Biogeosci. 2022 Dec 1;128(4):2022jg007293. doi: 10.1029/2022JG007293. Epub 2022 Dec 18.
The forests of south-central Chile are facing a drying climate and a megadrought that started in 2010. This study addressed the physiological responses of five stands across the Mediterranean-Temperate gradient (35.9 ° -40.3° S) using carbon isotope discrimination (Δ C) and intrinsic water use efficiency (iWUE) in tree rings during 1967-2017. Moreover, δO was evaluated in the northernmost site to better understand the effects of the megadrought in this drier location. These forests have become more efficient in their use of water. However, trees from the densest stand are discriminating more against C, probably due to reduced photosynthetic rates associated with increasing competition. The strongest associations between climate and ΔC were found in the northernmost stand, suggesting that warmer and drier conditions could have reduced C discrimination. Tree growth in this site has not decreased, and δO was negatively related to annual rainfall. However, a shift in this relationship was found since 2007, when both precipitation and δO decreased, while correlations between δO and growth increased. This implies that tree growth and δO are coupled in recent years, but precipitation is not the cause, suggesting that trees probably changed their water source to deeper and more depleted pools. Our research demonstrates that forests are not reducing their growth in central Chile, mainly due to a shift towards the use of deeper water sources. Despite a common climate trend across the gradient, there is a non-uniform response of forests to climate drying, being their response site specific. Keywords: Tree rings, stable isotopes, tree physiology, climate gradient, megadrought, climate change.
智利中南部的森林正面临气候变干以及始于2010年的特大干旱。本研究利用1967年至2017年树木年轮中的碳同位素分馏（ΔC）和内在水分利用效率（iWUE），探讨了地中海 - 温带梯度（南纬35.9° - 40.3°）上五个林分的生理响应。此外，在最北部的地点对δO进行了评估，以更好地了解特大干旱在这个更干燥地区的影响。这些森林在水分利用方面变得更加高效。然而，最密集林分的树木对碳的分馏作用更强，这可能是由于竞争加剧导致光合速率降低。在最北部的林分中发现气候与ΔC之间的关联最强，这表明温暖和干燥的条件可能降低了碳的分馏作用。该地点的树木生长并未减少，并且δO与年降雨量呈负相关。然而，自2007年以来发现这种关系发生了变化，当时降水量和δO均下降，而δO与生长之间的相关性增加。这意味着近年来树木生长与δO相互关联，但降水并非原因，这表明树木可能将其水源转向了更深且更匮乏水的区域。我们的研究表明，智利中部的森林并未减少其生长，主要是由于转向使用更深层的水源。尽管整个梯度上存在共同的气候趋势，但森林对气候干燥的响应并不一致，其响应具有地点特异性。关键词：树木年轮、稳定同位素、树木生理学、气候梯度、特大干旱、气候变化
