Decay or not Decay!

I tend to put things by. These roses had been discarded as they were past their best. That was six years ago. I saw a block of wood on a bookshelf and found them still in suspended animation. I can assure you the roses are authentic. I wonder why some things crumble away quite quickly while others remain the same? I remember finding a wren that died when it flew into the glass of a window. It lies perfectly preserved on another shelf, together with a goldcrest.