[Orofarne]

As a born and bred mountain girl, I know that small fires are actually beneficial to the forests. They burn out leaf litter and dead pinecones and things (called mast) and give all the trees more room to grow. The bottoms of many forest trees have really thick bark, so that the fires don't hurt the important insides of the tree. As long as the fire doesn't get way out of control and start jumping from treetop to treetop, it is very good for the forest.
Maybe the orcs did some amatuer firefighting and snuffed out the little fires before they could get rid of the mast and this tree was looking forward to a nice little (emphasis on little) forest fire.