They would talk about the wind, and how the world is doing, I suppose. Maybe about what they're feeling and how their leaves are doing.
Something like that, I suppose.
the clearing of trees is deforestation
Well, it depends on the type of tree and the disease but in general, a forest with many types of trees probably has a better survival rate as diseases can affect certain types of trees differently. So if you had a disease that could kill one type of tree and a forest made only of that type, all the trees would die.
A pinewood forest is simply a forest whose trees are mainly coniferous. A thriving natural pineforest may be found above the treeline where other broadleaf trees would struggle to survive.
The commonest terms would be a stand, woodland, forest of trees.
in the trees
In a forest
trees
animals,trees,ponds,waterfall,etc
the soil would be eroded
Trees convert carbon dioxide into oxygen, provide homes for numerous animal species, and fight soil erosion with their roots. If their were any major changes in tropical rain forest then there would be a major effect on the Earth because we and many other species depend on trees to survive; in other words without trees (rainforests) we would most likely die.
The opposite of dense could be thin, sparse, uncompressed, lightweight, or rarified (in the case of gasses).For populations, the opposite could be scattered or meager.
It would become a forest.