We took a pine (P. mugo) as well (published) and beech (Fagus) from the same family as Quercus (unpublished).

Our main finding, possibly/potentially relevant for your research area as well, is that at the decade time scale land use history/change (abandonment of pastoralism) is the driver rather than climate change.

Another issue is the rarity of meteorological stations at and near the alpine treeline. Extrapolation as by WorldClim may be very inaccurate (see our bear article in the same research area as the P. mugo study).

Hope it helps in your research design

Almost All plant species distribute normal in a gradient of the variable that most contributes to the dispersion. For example an altitude gradient displays the lowest range (given by the probability of the X value with a z

Beech is good for that

Generally speaking, almost all the native species are suitable.

However, from the practical point of view, it is necessary to take into account also the previous use by human population and if the distribution of a species is effectively correspondent to its potential distribution.

As an example, we studied the elevation shift of Picea abies and Larix Decidua in the Italian Alps.

Article Monitoring spatial and temporal pattern of Paneveggio forest...

In our case it is fundamental to know where the upper potential limit is reached thus we can say that the plants that will grow at higher elevation are exploring unprecedented height. On the contrary, if the potential limit was influenced by cuttings or pasture or any other reason this means that at present times the treeline is much lower than it should be and part of the occurring regrowth is due to the reconquering of an already suitable space.

This situation is quite frequent in the European Alps.

I hope it help you to clarify some issues,

all the best,

Marco