To many in the modern world, “logging” is a dirty word. It conjures up imagery of men with chainsaws deforesting a landscape and destroying the environment. Nothing can be farther from the truth. While both chainsaws and clearcuts are still tools used in modern forestry, in reality, foresters, loggers, and landowners use a large toolbox of different types of logging and timber harvests at their disposal. They use these tools not to destroy the landscape, but to manage the forest in the best, most sustainable way possible and ensure the forest maintains healthy growth for generations to come. This is truly at the heart of all forestry.
To understand more about the different types of logging and how they are used to the benefit (and not detriment) of the forest, one must understand that every harvest can be broken down into two pieces: the harvest system, which dictates the type of machinery used during harvest, and the silvicultural system, which dictates which trees are cut and the long-term objectives of the harvest. Each system has a unique role in forest management and provides landowners a different means to manipulate the forest’s future trajectory. In this article, we will examine both these pieces and the tools available, but let’s start with silvicultural systems.
What is silviculture? The United States Forest Service defines silviculture as “the art and science of controlling the establishment, growth, composition, health, and quality of forests and woodlands.” In other words, when a logger removes (or retains) a tree with a purpose of enhancing the qualitative and quantitative attributes of the forest, that is silviculture. These decisions are not random, however. They are methodical and follow the blueprint laid out by a forester. In the business, we call these blueprints silvicultural prescriptions, and they generally fall into one of five categories: Shelterwood, seed tree, clearcut, selection cut, and thinning.
A shelterwood system aims to harvest a portion of standing timber and regenerate the stand by allowing retained trees to spread seed while creating enough gaps in the canopy for light to reach new seedlings. Once seedlings have sprouted, the retained canopy continues to put on growth for future harvests while providing shelter to the new seedlings in the form of shade from harsh suns and protection from ice, winds, and any other environmental hazard that may pose a threat to seedling survival. This is why it is called a “shelterwood.” You can see the progression of a shelterwood harvest in the illustration below.
With this type of logging, there are typically typically two timber harvests: the establishment cut, which creates gaps in the canopy and allows for the stand to regenerate, and the shelterwood removal (or overstory removal), which removes the remaining mature trees once the understory is healthy and established. Eventually, the understory matures into a new stand of timber, and another establishment cut can be implemented, continuing the cycle. While these are separate harvests, they together represent a shelterwood silvicultural system.
The benefit of this system is that it allows for the natural regeneration of a stand without the need for expensive planting operations or other treatments. Unfortunately, spacing out the canopy enough to regenerate the stand can lead to blow down risks, and excessive stand entries can lead to damage of both the understory and residual timber. Despite these downsides, shelterwood cutting remains a mainstay of modern forestry practices and is one of the favored types of logging for managing well-suited species in the right stand types. To read more about this complex system, we have a more detailed piece you can read here.
Similar to a shelterwood, a seed tree cut is a type of timber harvest that aims to mimic natural stand regeneration. However, there are a few key differences. In a seed tree harvest, far fewer trees are retained. The trees that are left for seed may just number a couple per acre, depending on the circumstances. At this level, retained trees do not offer any “shelter” to new seedlings. Their only purpose is to spread seed. In fact, because the density of these trees is so low, it is, in most circumstances, not even worth it to come back to harvest these trees. Instead, they are left as legacy trees for the benefit of wildlife, particularly birds of prey. This is a goal many harvests seek regardless In many ways, these trees are sacrificial, but the sacrifice is not in vain! Thanks to the seed proliferation of these trees, foresters and loggers can keep the forest healthy and productive for generations to come.
Because these trees must have healthy enough crowns to spread seed far and wide and be strong enough to support itself out in the open against harsh winds, ice, and snow, individuals are often hand-selected by foresters, so proper seed tree harvests require careful planning.
By far the most famous (or infamous) of the types of logging, clearcutting is a silvicultural system that removes all standing timber from an area. In some cases, this can also be a method of natural regeneration, especially for species like aspen that can regenerate through stump sprouts and root suckers after a disturbance. In other situations (usually on smaller acreage), clearcuts may be left to seed in over time. Even if there are no seed trees or shelter, seeds will fall in from the edges, and the wind will blow lighter seeds like samaras into the cut. Additionally, certain pioneer species like aspen and cottonwood are designed to disperse seed far away into natural disturbances such as recent burns and man-made disturbances like clearcuts!
In most cases, however, clearcutting is used in conjunction with planting. In these situations, clearcutting has the benefit of giving land managers much better control over the future trajectory of the forest. Species, density, and even vigor can be controlled for, allowing for optimum growth. Unfortunately (though unsurprisingly) these operations come at great expense, so they must be planned carefully. Contrary to popular belief, there is a large amount of consideration that goes into every clearcut. If you want to read more about it, we have an article on the reasons why timber companies may plant trees.
All of the previously mentioned systems fall under a label known as “even-aged management.” In other words, they are generally used when trees in a stand are of the same age class, or when it is the objective of the harvest to create an even-aged stand over time. However, forests are nothing if not variable, and so often un-even aged management must be used. Most prominent in this class is the selection cut.
A selection cut is arguably one of the most complicated types of logging if only because it is less a system and more a methodology. While there are many variations, broadly speaking, selection cuts focus on selecting for harvest trees or groups of trees based on their own merits of species, quality, and growth potential with the aim of enhancing growth of desirable individuals while proliferating regeneration of valuable species. Over time, these cuts will create multi-aged stands in perpetuity, and the acreage will always be well-stocked with a certain percentage of mature and immature growing stock. You can see this process illustrated in the diagram below.
Not all timber harvests have to be a means of regenerating a stand. There are certain types of logging, known as intermediate treatments, that primarily focus on improving growth or quality of standing timber. Primary among these harvests is thinning. As a group of trees grows larger, they begin to compete with each other more and more. Their limbs shade each other from the sun, and their roots fight with each other for nutrients and space. They cannibalize each and hinder the growth of the entire stand. Thinning focuses, as you may have guessed, on thinning out these dense stands, leaving the best, most healthy and desirable individuals plenty of room to grow. The result is a faster growing stand and one that will be much more healthy and vigorous for far longer. Additionally, if a regenerating cut like a shelterwood is to be done at a later date, thinning helps prepare stands for these treatments and reduces the risk of blow down from canopy gaps, as larger trees and better crowns makes trees better able to withstand wind and stress. We have more information on thinning here.
Thinning is one of the most versatile types of logging because of its wide range of benefits. Not only does it create financial return for the landowner, but it allows for faster growth and gives land managers more silvicultural options when the stand is ready for a final harvest. Done properly there are few downsides. The only caveat, is that you need the right harvest system to be able to maneuver through tight, small trees.
All this silviculture is nice in theory, but it only works if one has the means to harvest the timber in the first place. Luckily modern forestry has at its disposal a great many types of equipment to get the job done, each with unique advantages and disadvantages that can aid in the success of the overall harvest objectives.
Yarding: Cable Skidder
The conventional logging system is one of the oldest and most classic types of logging. Trees are felled with a chainsaw and yarded with cable skidder, which uses a winch to drag trees across the ground out to the road. Traditionally, the feller manually limbs and bucks trees with a saw, but some conventional systems utilize a delimber to buck and delimb faster.
Conventional systems are ideal for smaller woodlots and sensitive sites. They have lower production rates than more mechanized systems, but the small equipment is gentle on the soil and minimizes damage to residual timber. They are a mainstay of low-impact logging.
More on the modern and mechanized side of the spectrum, we have the cut-to-length harvest system utilizing harvesters for felling, limbing, and bucking, and forwarders for yarding. Trees are limbed and processed in the woods, and wood is brought out to the yard already cut to specification, hence the name “cut-to-length.” Unlike conventional logging systems, these systems are fully mechanized with all functions fulfilled in the seat of a cab.
As far as mechanized systems go, the harvester has the unique advantage of incredibly articulate machinery, allowing it to reach in hard places that most larger equipment can’t get to. By limbing trees in the woods, it also creates for itself a bed of protective slash to drive over, allowing for better waste disposal and more protection for sensitive soils. Unfortunately, these machines have little control over felling direction, and moving trees around to limb can be a problem, so these machines don’t always protect regeneration and residual timber all that well.
Felling: Feller Buncher
Yarding: Grapple Skidder
Similar to cut-to-length systems, whole tree systems are fully mechanized, but that is where the similarities end. Whole tree systems harvest trees with feller-bunchers and drag the “whole tree” out to the yard using a grapple skidder. A delimber then removes branches and stacks wood without cutting logs to length. Trucks then bring the wood to the mill where it is processed further.
Feller-bunchers may not have the articulation of harvesters, but by being able to pick trees up off the stump, fell-buncher offer a great deal more control, protecting regeneration and residual timber. Unfortunately, grapple skidders apply more pressure to the ground, making the system unfit for sensitive sites. The differences and advantages of whole tree and cut-to-length systems are complex, so if you are interested, we have a separate article about it here.
Yarding: Cable Yarder
All the aforementioned systems have one profound weakness: Steep slopes. In the western United States and Canada, where steep slopes are the rule and not the exception, a different system is needed. That is where cable logging comes in. Cable logging is similar to the conventional system in that it uses a sawyer and cable to fell timber and pull it out of the woods, but unlike a cable skidder, which uses a small winch affixed to a vehicle that ultimately does the pulling, cable yarders use cables affixed to semi-stationary towers that pull trees up and away from above.
Every Type of Logging Has Its Place in Forest Management
Clearly, forestry is a practice with a wide diversity of systems and methodology, but each has its unique place. Forests are diverse ecosystems with a high degree of variability. It only makes sense that our silviculture and timber harvests have the diversity and nuance to match. With all these tools in our tool belt, foresters, loggers, and landowners are positioned better than ever in human history to manage our forests and timberlands in the most economically and ecologically sound manner possible in the interests of promoting and protecting healthy and productive forests for generations to come.