To state the obvious, trees are not mobile, and because they have been growing in the same locality in a wood for thousands of years with a stable climate they are not very tolerant to change.
The evidence of this is easily observed from where you live. If you look at the trees in your locality and take note of the types and then travel North or South to where the temperature is 3C warmer or cooler, you will notice that the trees will be very different. This indicates that the trees grow where they have the climatic conditions to suit them and if you change the climate by 3C they will be under considerable stress even if moisture and nutrients remain the same.
The green/blue patches on the temperature map roughly equate to the mountainous regions.
This paragraph from New Zealand research by D. O. BERGIN and M. O. KIMBERLEY. into improving the success of collecting and planting the seeds of trees and the value of getting the climatic conditions right for survival, including altitude.
Totara growth. http://newzealandecology.org/nzje/1911.pdf
“ It follows that large-scale planting for ecological purposes, such as re-vegetation of former Totara forest areas, should use seed of local origin and similar altitude in order to obtain trees with the same genetic integrity and which are suited to the local climatic conditions”.
What they have found is that the temperature was 3C warmer and the sea levels were 12 meters higher. Sea level is not an issue here so we will concentrate on the 3C temperature rise.
The first thing that springs to mind is that the trees of the Pliocene period were not the trees we have today and even if some of them are very similar they would have been growing in a completely different region of the world.
Trees like CO2 and so they can be expected to grow faster if they have more of it but it has been found that the other elements, particularly water are more important. Research at the University of Western Sidney, where they are conducting many experiments on the effects of Increased CO2 and also changing rainfall patterns on trees shows that water supplies are the dominant factor in growth.
Explanation of the many types of research here.
A tree has a huge root system which is as important to it as its branches and it relies on microbes in the soil to be healthy. Additional acidity can be fatal and although acid rain is associated with sulphur from burning coal everything that affects the trees natural state can put it under stress and be detrimental to its health.
Prof Steve Running does an excellent talk on his work on the spruce trees in Montana. https://www.youtube.com/watch?v=LLL7t3tF7z8
Modern satellites use cameras in the infra-red light sector to observe the health of forests around the globe in ways that cannot be done on the ground and the results are becoming increasingly alarming.