162 years after first publication of ‘On the origin of Species’ still there is relevant scientific debate about several open questions within the evolutionary theory. Some of the topics under intense discussion are about the distribution of genetic variability within natural populations, selection patterns, life-history trade-offs, phenotypic plasticity, and their effects on evolutionary processes. To address these questions, I focus on big sized long-living forest tree species, organisms that pose certain difficulties for evolutionary studies given their long generation time. However, understanding adaptive and acclimation mechanisms in forest tree species is of paramount importance under current environmental context as worldwide forest decline has been detected and given that forests are pretty relevant carbon sinks at global scale. To address such questions, I took advantage of a Pine species genetic improvement program and its experimental device through a quantitative genetics’ approximation. Here, I will show two different study cases to discuss evolution related topics such as fluctuating selection as a mechanism to maintain genetic variability in natural populations, growth vs. tree defenses trade-offs and their context dependence and environmental triggers of phenotypic plasticity evolution. Finally, I will provide some discussion about the potential effect of these results when managing forest genetic resources.