Jon’s carbon post, and Patrick’s question “how does it all fit together?” reminded me that I hadn’t yet posted the paper “Forest carbon: an essential natural solution for climate change“, although I had intended to almost a year ago. This is the first paper I would give to anyone trying to put the forest carbon pieces together from the standpoint of “what are the different ways forests can be managed for carbon and other goals?”
The authors are Paul Catanzaro and Tony D’Amato at the University of Massachusetts. I really liked the clarification of sequestration vs. storage, and forest level versus individual tree sequestration. Their explanation of the basic concepts is very clear. And the authors take into account other landowner goals such as wildlife and timber.
Of course, this all is based on wet forests that naturally grow old and don’t get eaten by bugs nor burned up. We can see that for dry Western pine forests where restoration of fire is important, that some of these ideas wouldn’t work. Perhaps there is a similar paper for dry Western forests
Below are some of their specific suggestions for how to manage under New England conditions:
Size of Trees
Grow and maintain large-diameter trees, as they make up a disproportionate amount of the live aboveground carbon stored in a forest.
• Maximize a tree’s ability to store carbon by letting trees grow larger. For planned timber harvests, grow vigorous trees an extra 15–20 years past your harvest timeline, or 1″–2″ larger than your target diameter. Sometimes harvests are unplanned, triggered by events that do not allow the timber harvest to be delayed. In these cases, consider leaving additional retention trees on-site (see “retention tree” bullet below).
• When it is time to regenerate, use methods that maintain large trees across the forest. Example regeneration methods include irregular shelterwoods, selection methods, two-aged variants of clearcutting and seed-tree methods, variable-retention harvesting systems, and variable-density thinning.
• Designate large trees to permanently retain in your forest in the live aboveground pool, which will eventually be added to the deadwood pool. These “retention trees” can be individually scattered across the forest or in small groups of at least a quarter acre in size. In addition to the carbon-storage benefits, these large-diameter trees are excellent for providing wildlife with cavities and food, may be an important seed source for future trees, and have high aesthetic value. Groups of retention trees can be placed around areas of high ecological value, such as
vernal pools or other sensitive sites.
Establish a new age class of trees.
• Ensure that tree regeneration goals are met by addressing interfering vegetation (invasive plants) and excessive herbivory (e.g., deer and moose browse). Timely regeneration of species well-suited to the site and future conditions will ensure that there are trees in place to sequester and store carbon into the future.
Distribution of Tree Ages
Identify the appropriate combination of young and old trees to meet your goals, and develop forest resiliency through diversity.
• As previously described, carbon sequestration rates peak when forests are young and then decline with age. Carbon storage is maximized in old forests. Maintaining forests with multiple age classes of trees will provide a balance of large, older trees for storage and younger, faster growing trees for sequestration. In addition, multi-aged forests increase a forest’s resiliency to natural disturbances (see “Forest Resiliency”).
• Trees of different ages often vary in height, which increases the vertical structure within the forest. Forests with multiple layers will store more carbon. Implementing strategies that allow for the development of a multi-aged, stratified forest will provide the opportunity to increase the levels of “carbon packing.”
Identify the appropriate mix of tree species to meet your goals, and foster forest resiliency through diversity.
• Establishing and promoting native, locally adapted tree species that have no known forest-health issues and that are predicted to be competitive in future climatic conditions— especially drought tolerant—will help achieve a vigorous forest.
• Promoting a diversity of species will increase the forest’s resilience to natural disturbances by ensuring that diseases or insects that kill one species will not kill an entire forest.
• Promoting trees such as red oak and white pine, which have the capacity to become dominant and grow very large, can increase forest carbon storage.
• Tree species have different wood densities. Promoting tree species with high-density wood that can grow to be dominant trees can increase carbon storage in a forest. For example, hardwood trees are denser than softwood trees. There are even differences among hardwood species. For example, red oak and sugar maple are denser than red maple.
• Promoting shade-tolerant trees (e.g., sugar maple), which can grow in the shade below the main canopy, can help increase the number of live trees growing in the forest, maximizing the opportunity for carbon packing by creating forests of multiple layers.
Promote increases in the deadwood pool.
• Designating retention trees will ensure a future source of deadwood, as the trees are left on-site until they die.
• Work with a forester to establish utilization standards that maximize the amount of slash left on-site, and include these in your contract.
• Felling or girdling poor-quality trees will add to the deadwood pool while also providing habitat benefits and freeing up space and resources to increase the growth rates on adjacent trees.