Planted in rows these tall straight trees are the result of continuous management.  When they were young, there would have been many other young conifers growing in the rows.   This encouraged competition between the individual trees.  Many of them grew rapidly and straight up to get most light and space, gaining advantage over the others.  

The weaker slower growing trees were thinned out by foresters, giving the stronger trees an even better advantage.  This thinning process has continued over the years, leaving only the very "best" trees surviving.  The aim in producing trees with long straight trunks is that we can get a large yield of good quality timber.   This will be used for making every day items as furniture, telegraph poles, pencils and paper.

Trees managed in this way are a renewable resource.