I have a 20 yr old American purple stem willow tree it is not very big, about 9 or 10 foot tall and about 9ft diametre. Apparently they stay fairly small. Its leaves have started to go yellow, not sure if its because of the new slabbing around it or that it will be getting less water or if its normal for the leaves to go yellow at this time of year

I have just had the area slabbed around it to extend the patio and while this was being done some of the roots (I'm pressuming it was the roots from the willow) were chopped off as the area was dug to about 5 or 6 inches before the slabs were laid so it has lost 5 or 6 inches of top soil over a 15ft by 15ft area. The gaps between the slabs have been filled in and under them will now be the sand and cement mixture which was put in all the corners so there will be gaps under there too with no soil.

I don't really want to lose it, next to the trunk there has been left quite a small area about 18 inch square which has been filled with soil.

Could it be that it has to recover from the roots being chopped a bit or will it be lack of water? I thought with it being there for 20 years that it might withstand it as its root system was well established. Will it recover?