Some types of purebred livestock enterprises involve saving a large percentage of the females as replacement dams. Dairy cows are an example of this type of enterprise. Heavy milk production limits breed-back, they have only one calf at a time and they do not have a very long production lifespan. Beef producers will typically keep about 1/3 of their heifer calves because a typical beef cow will only produce six or seven calves in her life time. That still limits the amount of selection pressure a producer can exert on his herd.
Plants, on the other hand, produce hundreds-to-millions more progeny than "replacement". That allows the grower to exert much higher selection pressure. A serious tree grower does not need much of a reason to cull a tree, and the sooner it is done the sooner the neighboring trees are released from the competition.
|Three Quercus robur, European Oak, the oak of Robin Hood, Sherwood Forest and all of that. The one on the left will be culled because the other two trees have better geometry.|
|This tree is not a dogwood, it is a Red Maple. It never developed interesting fall color. I will replace it with Q. lyrata hybrids because I like Oak trees.|
|These Norway Spruce will be thinned out. I noticed that many of the spruce trees in Eaton Rapids are in decline, most likely due to Phomopsis. Engelmann and Blue Spruce are most vulnerable but it is hammering the Norway Spruce as well. There is little the owner can do except to try and keep the tree(s) in a robust state of good health and to maximize airflow. Reducing crowding accomplishes both.|
|You can see that I get a lot of help from the dogs. Marking trees is their specialty!!! This is a chestnut tree that winterkills during severe winters.|
Life is better when you have more of the first kind of tree (or cows or sheep or hogs....) and none of the second kind.