Tree mortality and its relationships with forest structure and environmental factors have been studied for many decades using permanent plots. In the last decades, plot monitoring showed that tree mortality rates were increasing in tropical and temperate regions. We analyzed tree mortality in subtropical montane forests of Northwestern Argentina to: (i) compare tree mortality rates between secondary and old-growth forests, (ii) describe relationships between tree mortality rates with elevation, climatic variables (mean annual temperature, total annual precipitation, temperature and precipitation seasonality), productivity, plot-mean wood, density and plot-mean square diameter, and (iii) analyze long-term trends of tree mortality rates at plot and species level. We used 54 permanent plots monitored for 25 years (1991–92 to 2016–17) to analyze individual-based mortality and basal area mortality rates. We found that tree mortality rates decreased significantly with elevation, precipitation seasonality, plot-mean wood density and plot-mean square diameter, and increased significantly with total annual precipitation, mean annual temperature and productivity. Individual-based mortality increased between 1991–92 and 2016–17 in old-growth forests. Although the main drivers of increasing tree mortality over time remain unknown, we suggest that it may be related to the increasing precipitation and temperature that occurred in the last decades in this region. Further research with forest plot monitoring is necessary to understand causes of increasing mortality and the consequences for forest structure, composition and dynamics in the long-term.

几十年来，人们一直在使用永久性地块研究树木死亡率及其与森林结构和环境因素的关系。在过去的几十年中，地块监测表明热带和温带地区的树木死亡率正在上升。我们分析了阿根廷西北部亚热带山地森林的树木死亡率，以：(i) 比较次生林和原始森林之间的树木死亡率，(ii) 描述树木死亡率与海拔、气候变量（年平均气温、年总降水量）之间的关系、温度和降水季节性）、生产力、地块平均木材、密度和地块均方直径，以及 (iii) 在地块和物种水平上分析树木死亡率的长期趋势。我们使用监测了 25 年（1991-92 至 2016-17）的 54 个永久性地块来分析基于个体的死亡率和基区死亡率。我们发现树木死亡率随海拔高度、降水季节性、地块平均木材密度和地块均方直径而显着降低，而随年总降水量、年平均温度和生产力而显着增加。在 1991-92 年和 2016-17 年间，原始森林的个体死亡率增加。尽管树木死亡率随时间增加的主要驱动因素仍然未知，但我们认为这可能与该地区过去几十年降水和温度的增加有关。有必要对森林地块监测进行进一步研究，以了解死亡率增加的原因以及对森林结构的影响，