For this answer what you need to understand is that, almost all of the rain forests we see in the world today have a huge effect on the rain we have and temperature.
First of all, the amount of water in this area of ten mile of trees will increase a lot, this happens because when the trees were there, they used all this water to produce energy for its survival, but now, they can't have it anymore because they were removed, so there won't be enough plants to absorb this water, and if so, it'll take a longer time than before.
About the amount of oxygen in the area, it'll be affected too, but let's think for a second, Amazon in Brazil is a huge forest, but this is not the main oxygen producer for the world, they are more likely a temperature controller. Oxygen is produced mostly by seaweeds, but that doesn't mean that the oxygen graph in this area won't drop, it will, but it won't be a huge one.
