Global Climate Models project that observed climate trends are likely to be preserved and the number of extreme events will be increasing during the rest of the 21st century, which may have a detrimental impact on forest ecosystems. These impacts may include forest decline and widespread dieback of the most vulnerable biomes, such as the Mediterranean Forest of Central Chile (MFCC). Nothofagus macrocarpa and Austrocedrus chilensis are two canopy-dominant, endangered tree species in the mountains of MFCC. Here, we project tree growth of these species based on tree-ring width chronologies, a simplified version of a process-based model, and climate change projections. We used the tree ring information derived from ~400 trees from 12 sites distributed across MFCC in combination with the simplified version of process-based Vaganov-Shashkin tree-growth model (VS-Lite) to forecast changes in tree growth for the next four decades. Tree growth projections were made on the basis of monthly values of temperature and precipitation from the output of 35 climate models based on two ensembles of CO₂ emission scenarios of the IPCC AR5 (RCP 8.5: higher-emission scenario, and RCP 2.6: lower-emission scenario). For the MFCC region these scenarios result in temperature rise ranging between 0.5 °C and 2.0 °C, and a precipitation decrease between 5% and 20% by the year 2065, as related to historical conditions. Our results showed that the VS-Lite model is capable of reproducing tree growth decline during the recent extreme dry period, i.e. 2010–2018, which supports its use for tree growth projections in the MFCC region. According to the modeling results, we find that tree growth in both N. macrocarpa and A. chilensis forests distributed in the MFCC region will be adversely affected by future climate changes, mainly starting from the year 2035, under both scenarios. Our work provides evidence of the degree of vulnerability of Mediterranean mountain forests in central Chile according to current climate change projections. The projected decline in tree growth indicates serious risks in the dynamics and survival of these forests relatively soon, so alerts are given about this situation which may require to counteract the deleterious effects of global change on vegetation in this region.

全球气候模型项目认为，观察到的气候趋势可能会得到保留，极端事件的数量在21世纪剩余的时间内将会增加，这可能会对森林生态系统产生不利影响。这些影响可能包括森林砍伐和最脆弱生物群落（例如智利中部地中海森林（MFCC））的广泛灭绝。Nothofagus macrocarpa和Austrocedrus chilensis是MFCC山区的两种主要树冠，濒危树种。在这里，我们根据树轮宽度年表，基于过程的模型的简化版本以及气候变化预测来预测这些树种的生长。我们使用了从分布在MFCC上的12个站点的约400棵树中得到的树年轮信息，结合基于过程的Vaganov-Shashkin树增长模型（VS-Lite）的简化版本，预测了未来40年树的变化。树木生长的预测是基于35个气候模型的输出（基于两个CO ₂集合）的月度温度和降水量得出的IPCC AR5的排放情景（RCP 8.5：较高排放情景，RCP 2.6：较低排放情景）。对于MFCC地区，与历史条件相关，到2065年，这些情景导致温度升高范围在0.5°C至2.0°C之间，并且降水量减少5％至20％。我们的结果表明，VS-Lite模型能够重现最近极端干旱时期（即2010-2018年）的树木生长下降，这支持将其用于MFCC地区的树木生长预测。根据建模结果，我们发现N. macrocarpa和A. chilensis的树木均生长在两种情况下，分布在MFCC地区的森林都将受到未来气候变化的不利影响，主要是从2035年开始。根据当前的气候变化预测，我们的工作提供了智利中部地中海山区森林的脆弱程度的证据。预计树木生长的下降表明这些森林的动态和生存相对较快地面临着严重的风险，因此对这种情况发出了警告，这可能需要抵消全球变化对该地区植被的有害影响。