Generally, the recently thinned areas are more like the unmanaged areas compare to the formerly thinned areas. The eclipses of figure 5 shows that recently and unmanaged areas are related to each other and separated from the formerly thinned areas.  When analysing differences in effect of different response variables, leaf thickness was significantly affected by the explanatory variables. There was no clear trend of the effect on vitality when canopy cover and tree density increase.

Several studies have found a correlation between available light levels and an increasing of thickness, number of stomatas, weight, weight/Cm² and vitality. Based on the means of canopy covers in this study, we could not except any differences in leaf morphology between the groups due to no significant difference in canopy covers between these groups. The results in this study showed that it is small differences between the different groups. The differences are however biological small, so it is difficult to draw any big conclusions from it. The results from this study shows that it is not possible to draw those conclusions beforehand, it seems to be sites and population-dependent of how trees and leaves are reacting when the light levels increase.

Based on the means of tree densities. Most were thinned in the formerly thinned areas. One explanation could be that those areas had the biggest overgrowth problems of the groups. That could also be one reason why the vitality is lower (even if it is small differences between the groups) in the formerly thinned areas. The need of restauration was higher in the formerly thinned areas compare with the other managements. The oaks in the unmanaged areas have the highest vitality and for that reason are they still unmanaged because they are not showing any need of conservation.

Because Eschrich 1989 find that buds of beach had adapt to the available sunlight levels during late July/ early August. Because the recently thinned areas were thinned between late autumn / or early winter, it is not possible to expect that the oaks in this group had adapt to the new light levels when leaves from them were sampled. Because of that, we would expect that the leaves from the recently thinned areas should be more similar to the unmanaged oaks that to the formerly thinned oaks. This is exactly what is possible to get from the RDA-plot where group two and three (recently thinned and unmanaged oaks) are close to each other while formerly thinned areas are separated from the others.

One thing that has not been analysed in this study is site-specific parameters as access to water, access of nutrients, genetic variation between oak populations, water flow etcetera. Eight percent of the variation in the response variables could be explained by the explanatory variables tree density and canopy cover. Because these number is such low, it is hopefully other parameters who were not analysed in this study who have bigger impact on leaf morphological parameters and vitality. Because the summer 2018 were extraordinary with drought and high temperatures, it is possible to draw the conclusion that this summer had a big impact on the tree vitality. Thomas and Hartmann 1998 noted that the available level of water was lower in unhealthy stands of oaks in north-western Germany. The same study also concluded that that oaks in these unhealthy oaks had a reduce biomass and root density due to unfavourable soil-water relations. The unfavourable relations can further contribute to crown damage and therefore lead to a decreasing in vitality (or mortality). These results indicate that plant-water relations can affect the mortality and vitality. Because the summer 2018 were extraordinary dry and hot which lead to very low ground-water levels, we could expect that vitality should decrease during that time.

Because the recently thinned areas were grown in a geographical restrict area, we can expect that they are closely related to each other. That means they are sharing similar genes and have similar preconditions. It means that all trees in this area have almost the same living conditions, while the trees from the two other groups come from geographical separated sites with various living conditions are not sharing genes and have not similar preconditions. Because the recently thinned oaks are sharing genes, it is likely that the hole population have genes that are either drought tolerant or drought non tolerant and that all oaks have almost the same drought tolerance. It is different in the other groups, where the oaks came from more geographical separated areas where the oaks should have different drought tolerance due to genetic variations. The adaptations to water stress should be more various in the formerly thinned areas and the unmanaged areas due to more separated areas and therefore more genetic variation. Because of geographical separated areas, it is hopefully different oak populations who are studied in those groups. The results between these should be more site-dependent because different populations have different opportunities to adapt to extreme weather.

The oaks from the recently thinned areas had not adapt to the new available light levels and were therefore more like the oaks from the unmanaged areas. When the different parameters are analysed one by one, it is not possible to see the same clear trend who other studies did. Other studies find that stomatas, thickness, weight etcetera increases with an increasing of light. The results from this study are not showing the same clear relationship. It seems like it is more site-dependent then management dependent why leaves are adapting in different ways in the different groups. Another conclusion is that tree density and canopy cover are not affecting tree vitality in so much that was expected beforehand. It seems like other parameters who was not studied in this study have bigger impact on vitality then those who was studied in this study.