In Germany, the bees that help with flower pollination are dying and evidence can be seen on the streets and under trees, this has resulted to import of bee eggs from other countries to be released in the orchards to increase fruit yields. And we all know that pollination is a process that enabling fertilization and reproduction thereby increasing trees and forest.

Than you Dear Banson for contribution. You draw attention exellent point that effects of climate change on bees population.

Physical evidence of the impact of global warming and climate change on forests are being  studied world over, however, only few have been studied in reported with good insight. Researchers have reported alpine treeline ecotone moving upward due to warming and CO2 enrichment. There has been phenological shifts in vegetation. Thermophilic lichens are showing range shifts. Coral reef being sensitive to change in SST are getting bleached etc. There are good literature on these topics but we need to work more to really quantify the degree and directions of such changes.

My Dear Ugur Kezik; Here are few very important links which will help in your research work. regards

http://www.sciencedirect.com/science/article/pii/S0169534799017644

http://www.nature.com/nature/journal/v453/n7193/abs/nature06937.html

http://www.nature.com/nature/journal/v452/n7190/abs/nature06777.html

https://www.researchgate.net/publication/269190817_Soil_warming_and_CO2_enrichment_induce_biomass_shifts_in_alpine_treeline_vegetation?ev=prf_pub

Article Soil warming and CO 2 enrichment induce biomass shifts in al...

Dear Master Dubey, thank you very much for your valuable contribution. and what do you think about change of phenology and phenological vegetation period due to climate change as the mentioned (in a piece) in the first article you attached ?

Dear Christopher,

Thank you very much for contrubition. I reviewed the summary of the article you sent and Its really valuable and clear study. have you used just  temperature and CO2 paramaters?  I wonder about annual precipitation which parameter is affecting plant growth condition significantly. So, what do you think about that?

Dear Ugur

Actually, there plenty of evidence to support the climate change impacts on forests, to name one, the changes in stratospheric ozone levels have tended repercussion on the levels of rainfall in the Southern Hemisphere, you can check this inP. Gonzales research.

http://www.ldeo.columbia.edu/res/div/ocp/pub/seager/gonzalez_etal_2013.pdf

http://www.cpc.ncep.noaa.gov/products/outreach/proceedings/cdw37_proceedings/PGonzalez.pdf

Dear Ugur

Hope this will help a little....................

http://www.ccfm.org/pdf/TreeSpecies_web_e.pdf

http://www.fs.fed.us/wwetac/projects/PDFs/BioScience_CC_and_Bark_Beetles.pdf

For a general discussion of this and related problems, see my 2012 book, "the Moon in the Nautilus Shell," which has several chapters on climate change and its possible ecological effects. 

There are many studies on impact of climate change & global warming on forest , other natural environments or ecosystems.Some are mentioned above by the answers already given by experts . An in depth literature  survey will definitely throw light on these aspects. 

Thank you Dear Unnikrishnan Narath Nandakumar  for your additions.

You may like to see this:

Climate change impacts in European forests: the expert views of local observers

http://link.springer.com/article/10.1007%2Fs13595-013-0280-1#page-1

Thank you dear Hormoz Sohrabi for your contribution.

The physical evidences of the impact of global warming and climate change on forests can be:

1. Change in Rainfall pattern

2. Loss of biodiversity

3. Presence and absence of bio-indicators

4. Shifting of weather patterns etc.

Global warming has the following effects:

1. Global warming is increasing the average temperature of our earth due to green house gases.

2. Global warming has responsible for many extreme weather events like floods, natural fires and drought in many parts of world.

3. it is responsible for loss of biodiversity due to change in weather pattern and climatic conditions.

4. it is enhancing the water and airborne diseases.

5. As you mentioned it is also responsible for melting of glaciers.

6. it is responsible for climate change.

7. it is responsible for rising the sea level.

8. it can decrease the crop yield in future.

9. it may be responsible for for desertification and deforestation.