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Unfortunately, this can cause severe damage to your tree. This can be quite a difficult problem to correct. If the tree is short enough to reach and spray with something, then you can try boiling sliced hot peppers in water. Strain, and spray as much of the tree as possible.

That is actually a sweet gum tree. It will produce spiky seed pods that many people find annoying to step on and to mow over.

They height can vary by variety. Some of them will remain shorter than 10 feet, and some will go to 30.

This link will help: https://www.gardeningknowhow.com/ornamental/trees/sweetgum/sweetgum-tree-info.htm

Do you mean that there are other sweet gum trees near that change, or just other types of trees in general? This could depend on where you are located, as you could be just inside the area that they remain evergreen, or you could just have a hardy type that is more cold tolerant than others.

This article will give you more information about the tree: https://www.gardeningknowhow.com/ornamental/trees/sweetgum/sweetgum-tree-info.htm

You have a legitimate concern. If the sweet gum was removed this year, the stump grindings/ wood chips that remain below the soil grade will still be relatively "raw" and will require heavy nitrogen use for the decomposition process. If you plant in that spot your plants may suffer from Nitrogen deficiency. Other than digging the grinding out and replacing with new soil, you can apply a pound or two of high nitrogen fertilizer, Ammonium sulfate 21-0-0 or Urea 46 -0-0 , water it well and give it a month or two for the chips to start decomposition before planting.

Yes, but this chemical needs to be handled by a professional that works with them for a living. There is high risk for health, and environmental damage with misuse.

Here is an article that will help: https://www.gardeningknowhow.com/ornamental/trees/tgen/fruit-tree-sterilization.htm

Here is a link that will help you to find the closest extension service to you. They can help you with this task:

https://www.gardeningknowhow.com/extension-search

It could be that the size of the hole isn't accommodating to the size of the root mass. Digging the tree up may cause more shock than it is worth, however.

I would recommend testing the soil around the tree to make sure that the nutrient levels and pH are ideal. This will be the first step. Once you figure out what, or if the soil needs anything you can begin to correct it.

If this does not prove successful, then you can add worms and mulch! They are wonderful at aerating soil, and they will help feed the tree as it grows.

Here are some articles that will help:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm

https://www.gardeningknowhow.com/special/organic/the-importance-of-soil-for-an-organic-garden.htm

https://www.gardeningknowhow.com/ornamental/trees/sweetgum/sweetgum-tree-info.htm