Trees hold an incredible power, that being their ability to fix carbon from the atmosphere via photosynthesis and use it to produce a tangible product – wood. Wood is one of the most simplistic, yet complex materials on Earth, and wood products may be durable for centuries (i.e., long-term carbon storage) if kept under proper moisture and temperature conditions. The wood generated within Iowa forests, the base for a myriad of value-added products, fuels state, local, and farm-level economies – with associated forest product industries contributing ~$5B in annual economic output to the region! Compound benefits abound as well, such as clean water, wildlife habitat, and recreation.
Our state’s ~3 million acres of carbon-fixing friends are facing a multitude of threats, however, in the form of increasing extreme weather events and flooding, invasive species, and forest fragmentation. To top it off, we are also facing a serious dearth of forest management contractors to perform the vital work of forest management needed to address these threats. In my mind, the top two threats to Iowa’s forest are 1.) an overall lack of active forest management, and 2.) steep declines in promotion and adoption of once-prolific tree planting programs, notably riparian forest buffers (remember the late 1990’s?). If these two issues were addressed, Iowa’s forests would not only gain resilience to all current and emerging threats, but also reap the wide-reaching benefits of increased carbon fixation. More wood would certainly be good right about now!
Forests and Carbon: A (very) Quick Overview
Carbon represents ~50% of a tree’s dry mass – regardless of species. The mass of carbon stored within an individual tree depends on a number of factors, notably species, size, and age. Species impacts on total carbon mass storage per tree are heavily dependent on the species’ wood density. Wood is technically dead xylem (i.e., old conductive tissue), and wood density varies depending on the ratio of conductive vessel void space (i.e., the “pipes”) to the actual woody matrix. Thus, a cottonwood log (i.e., low-density species) would contain less carbon than a red oak log of identical dimensions.
Living trees, however, are not the only location of carbon storage within forests. In fact, 5 total pools exist: 1.) aboveground live-tree biomass (includes other vegetation as well), 2.) belowground biomass (coarse and fine roots), 3.) dead wood (both down and standing), 4.) litter (leaves, etc.), and 5.) soil (mineral and organic). In general, the mineral soil and aboveground biomass pools represent the greatest carbon mass storage in midwestern forests. When we talk forests and carbon, we need to think in terms of these collective pools, and not simply board feet of standing timber per acre. Forestry term alert – a board foot is a standard (U.S.) unit of wood volume measurement, and is equivalent to 144 in3, or the volume contained within a piece of wood having dimensions 12”x12”x1”.
Forests are not static – their structure and species composition change over time, and thus carbon storage mass is constantly changing as trees germinate, live, die, decompose, and regenerate. Change also occurs as species composition transitions from early-successional species (e.g., oak-hickory) to later-successional species (e.g., maple-basswood) through time and under various management systems. In general, the amount of carbon stored within forests increases as forests age.
In Iowa, forests store ~52 metric tons of C per acre (all pools combined), with aboveground live tree biomass and soil (mineral) representing the majority of this storage. As we manage forests and address threats (e.g., forest conversion), we must consider how our actions will impact carbon gains and losses across all pools. For example, consider how each pool would change following: 1.) the 2020 derecho, which produced unimaginable volumes of downed woody material primed for decomposition and slow carbon loss, versus 2.) development/loss of a 40-acre tract of forest in a Des Moines exurb (i.e., immediate carbon loss).
Forest Management for Carbon
Before we dive into forest management for carbon, it is important to define two key (and seemingly-similar) terms: carbon storage and carbon sequestration. Carbon storage refers to the amount of carbon presently stored within an individual tree or forest. Carbon sequestration refers to the process by which trees use CO2 and photosynthesis to store carbon as plant biomass. One overarching goal of forest management should be to increase forest vigor. Vigorous forests not only exhibit increased resilience towards current and emerging threats, they also work to increase carbon storage. At present, the nation’s forests remove 12-14% of U.S. annual greenhouse gas emissions through carbon sequestration.
Your individual forest management strategy will influence the amount of carbon stored and sequestered. However, a single cookbook recipe for carbon management will not apply to all Iowa forest ownerships – there are simply too many variations in soils, species composition, age, and management history. Certain primary concepts do apply to all landownerships, as far as management for carbon storage and sequestration.
Even though tree growth slows with age, forests (across all pools) gain carbon storage with age. Because of this, management for older forests is a desired strategy if carbon storage is a primary landowner objective. Older forests produce larger-sized trees suitable for long-lasting end uses (e.g., veneer, ties) that will store carbon for decades after harvest. Recall that the carbon storage potential of a species is driven by wood density. In Iowa, this represents an important opportunity to increase active forest management aimed at oak regeneration. Not only are oaks higher-density, but oak forests are decreasing in prevalence state-wide, due in part to natural forest succession (i.e., transition to later-successional species such maple/basswood) brought on by a omnipresent lack of forest management. Managing for oak regeneration is not easy – it requires diligence, and involves practices such as prescribed fire and even-aged management (e.g., opening/removing canopies to provide adequate sunlight to the forest floor).
In comparison to managing for older forests comprised of higher-density species, management for younger forest stands (e.g., early successional) and/or stands comprised of faster growing (often lower-density) trees would be the strategy to increase carbon sequestration. Two important opportunities in Iowa emerge here. First would be a resurgence in the promotion and establishment of riparian forest buffers – practices that often entail a high proportion of faster-growing species such as sycamore (not to mention the proven water quality benefits).
Second, early successional forest (e.g., young aspen stands in the northeastern part of the state) is experiencing a significant decline in prevalence on the landscape. Working towards reestablishing these forests would provide compound benefits, such as ruffed grouse habitat, along with increased rates of carbon sequestration. Anecdotally, private landowners who managed for a diverse (key word here) mix of younger and older forest stands suffered far less collective damage from the 2020 derecho that those whose lands lacked this diversity. Ideally, management for a mixture of both forest types would allow landowners to simultaneously increase both carbon storage and sequestration.
A (very) Quick Synopsis of Forest Carbon Programs
Trees and forests have value in offsetting carbon emissions, and thus several forest carbon offset markets have emerged. Within these markets, private landowners are paid by corporations and individuals (who are looking to offset their emissions) for the carbon storage and sequestration provided by their trees. Essentially, programs connect you with buyers, assess the carbon storage and sequestration value of your property, and help guide and provide resources for sustainable management to ensure value is not compromised over the term of the agreement. In general, payments range from $20 to over $200 per acre per year – heavily dependent on the program and individual property. Programs often offer landowners an array of project development, management planning, and verification technical services at no-cost.
Notable programs include Forest Carbon Works, CORE Carbon, NCX/Natural Capital Exchange (NCAPX), and the Family Forest Carbon Program (FFCP). Details on each are too extensive to list here, however, information on all four may be found at the respective links, and see “highlights” below. Good news for Iowans is that “smaller” landowners (< 40 acres) may now able to participate in some of these markets.
Items of interest for each program
Forest Carbon Works
- Open to private landowners across contiguous U.S.
- 40 acres of forestland minimum, but landowners must enroll ALL forestland owned.
- Credits recognized by California Air Resources Board (CARB, gold standard in C credits).
- No-cost technical service and carbon assessment, no fees. Extensive array of services provided.
- Available as of summer 2021, and entire U.S. will be rolled out in phases (contact to inquire on regional availability).
- 40 acres of forested land minimum.
- Credits recognized by American Carbon Registry (ACR).
- 40-year project terms, no cost to landowners.
- Technical service and management resources provided at no-cost.
- Open to all landowners across contiguous U.S.
- No acreage minimums and no fees for 1-year contracts (requirements may vary for longer-term contracts).
- Carbon potential assessed off-site, using remote sensing and regional economics.
- No project development or forest management planning technical service provided.
- Partnership between American Forest Foundation and The Nature Conservancy.
- Currently limited to pilot properties in mid-Atlantic states. Expanding to Lake States following. Contact FFCP on predicted Iowa availability.
- 10-20-year agreements, 30-acre minimum.
- Free project development, management planning, verification services provided.
Enrollment is a serious decision that should be made carefully, ideally after thorough discussion with your professional forester. Many stipulations, management commitments, and other expectations of landowners are associated with these programs.
Whether you enroll in a current or emerging carbon offset program or not, there are a multitude of actions and cost-share programs that Iowa forest landowners can take advantage of today, to get paid to enhance carbon sequestration and storage. These include the Conservation Reserve Program (CRP), the Environmental Quality Incentives Program (EQIP), and the Resource Enhancement and Protection Program (REAP). It all starts with engaging in active forest management and working closely with your professional forester.
P.S. – fall tree seedlings are currently on sale at the Iowa DNR State Forest Nursery. Now’s the time to get some young trees and shrubs in the ground and up your carbon sequestration rate!
Additional information on forestry and forest management may be found by visiting the ISU Extension Forestry website.