We have recently added on to a building and several trees had their roots cut and a sidewalk around them with a large circle of dirt and plants underneath. These are non bearing pear trees, is there something that can be done to ensure they do not die? Also a post oak tree at the end of the building had it's roots cut, it is a large tree and it does have some hollowness to it. Right now they are still looking good although this is a recent project. Does anyone have suggestions? My thoughts are the sick tree treatment but do not want to waste the money if these trees will die anyway. Thanks