Certainly there would be a short period where there is little to no new growth. The world covered in water brings with it a great deal of mud. Much of what was once on the face of the earth was buried under massively thick layers of mud. The point is that there were very few resources in the area and it makes practical sense that the ark was used for other purposes after the waters receded. Why would they keep it in tact? To what end?
Sure, but if it’s only 40 days, wouldn’t some of the trees survive? And we have no idea about how much was “just mud”, although that’s not the indication in the Bible. As someone mentioned, the olive branch....