A post-fire area of the Sierra Nevada mountains with negligible conifer regeneration. (Joseph Stewart, UC Davis/USGS)
In the aftermath of megafires that devastated forests of the western United States, attention turns to whether forests will regenerate on their own or not. Forest managers can now look to a newly enhanced, predictive mapping tool to learn where forests are likely to regenerate on their own and where replanting efforts may be beneficial.
The tool is described in a study published in the journal Ecological Applications by researchers from the University of California, Davis; U.S. Geological Survey (USGS), Cal Fire and the U.S. Forest Service.
“Huge fires are converting forested areas to landscapes devoid of living trees,” said lead author Joseph Stewart, a postdoctoral researcher at UC Davis and with USGS. “Managers need timely and accurate information on where reforestation efforts are needed most.”
The tool, also known as the Post-fire Spatial Conifer Regeneration Prediction Tool (POSCRPT), helps forest managers identify within weeks after a fire where sufficient natural tree regeneration is likely and where artificial planting of seedlings may be necessary to restore the most vulnerable areas of the forest.
The POSCRPT tool produces spatial predictions of post-fire forest regeneration. (UC Davis/USGS)
Fewer conifers expected
Conifers, or plants with cones such as pine trees, dominate many forests in western North America. The study found that conifers are less likely to regenerate after fires when seedlings face drier climate conditions, especially in low-elevation forests that already experience frequent drought stress. Overall, fewer conifers are expected to grow in California's lower elevations following wildfire due to climate and drought conditions.
“We found that when forest fires are followed by drought, tree seedlings have a harder time, and the forest is less likely to come back,” said Stewart.
A UC Davis team collected post-fire recovery data from more than 1,200 study plots in 19 wildfires that burned between 2004 and 2012, as well as 18 years of forest seed production data. Ecologists at USGS collected and identified over 170,000 seeds from hundreds of seed traps. The scientists combined these data with multispectral satellite imagery, forest structure maps, climate and other environmental data to create spatial models of seed availability and regeneration probability for different groups of conifers, including pines and firs.
Forest managers have used a prototype of the tool in recent years to better understand where to focus regeneration efforts. The new upgrade incorporates information on post-fire climate and seed production and includes an easy-to-use web interface expected to increase the tool's accuracy and use.
“This work is a great example of how multiple partners can come together to solve major resource management problems that are arising from California's climate and fire trends,” said co-author Hugh Safford, regional ecologist for the USDA Forest Service's Pacific Southwest Region and a member of the research faculty at UC Davis.
Additional co-authors include Phillip van Mantgem, Adrian Das, Nathan Stephenson, Jon Keeley and Micah Wright of USGS; Derek Young and James Thorne of UC Davis; Kristen Shive of Save the Redwoods League; Haiganoush Preisler of U.S. Forest Service; and Kevin Welch of California Department of Forestry and Fire Protection.
The study was funded by the USGS' Southwest Climate Adaptation Science Center, Ecosystems Mission Area and Land Change Science Program.
The University of California Agriculture and Natural Resources (UCANR) publications office today announced the release of a new book, “Reforestation Practices for Conifers in California”, a practical manual for landowners and managers that explains the why, where, who, when, what, and how of getting sustainable forests back into California's diverse landscape. It is available now for immediate viewing and downloading for free on the Forest Vegetation Management Conference's website: www.fvmc.org. Next year the book will be published in full color print and web format by
“The primary takeaway from this book is that the most successful reforestation happens if planning begins as soon as the flames die down,” said Dr. Bill Stewart, Co-Director, Berkeley Forests. “The manual presents a planning process, with a detailed explanation of the options at each step. These basic steps are the same for a small landowner, large landowner, or an agency.”
The recommended practices are the result of 50 years of concentrated effort to improve reforestation success and reduce costs under the difficult conditions present in most of California. Significant lessons have been learned since the last reforestation manual for California was published in 1971. The 16 co-authors of the new book present the best practices gleaned from their combined experience of planting over 100 million conifer seedlings on hundreds of thousands of acres of public and private land in the state. Funding for the preparation of this book was provided by the California Department of Forestry and Fire Protection (CAL FIRE), the U.S. Forest Service, and private donors.
Successful reforestation is nothing like landscaping a yard and going down to the nursery to buy a few fruit trees to plant and water in your backyard. Because reforesting burned forestland depends on natural precipitation and not costly irrigation systems, reforestation requires careful evaluation of the site and the availability of locally adapted native seeds. If seeds are available, then foresters prescribe treatments for the site and the quantity of seedlings of each species needed. Over the next two years, the forester will plan and implement site preparation, plant nursery grown seedlings, and arrange follow-up treatments as needed.
Bob Rynearson of W. M. Beaty & Associates, Inc, a forestland consulting firm in Redding, California and one of the book's authors explains, “Experience has shown controlling competing vegetation results in the retention of sufficient soil moisture for excellent seedling survival rates, even on very dry sites during prolonged droughts, when high quality, locally adapted native seedlings are planted properly. If you don't properly plan and implement the sequence of each time-critical reforestation step, then you're probably wasting your money, time, and valuable conifer seed.”
“To maintain the carbon capturing potential of our forests, significant investments in effective reforestation on private and public forest lands will be necessary,” said Dr. Stewart. “The bottom line is that achieving success is critical if the growing backlog of California's fire damaged forests are to once again be filled with healthy trees.”
The president of the non-profit organization Forest Landowners of California, Claire McAdams, is enthusiastic in support of the book: “The loss of family forests due to wildfires, often after one or more decades of ownership and careful husbandry, is emotionally gut wrenching. The new Reforestation Practices for Conifers in California publication by UCANR is an excellent guide to both the process and issues facing non-industrial forestland owners seeking to reforest their land. This publication belongs on everyone's reference shelf.”
Bill Stewart of the University of California' Berkeley Forests and Agricultural and Natural Resources is the technical editor for the project. “The final book includes more than 500 pages, 200 figures, and 800 scientific references. It will be a valuable resource for landowners, practitioners, and policy makers” he said. The process involved 16 co-authors and more than 25 peer reviewers. Given the time sensitive need to get this information out in the public arena while UCANR is completing the copy editing, final high quality illustrations, and hard copy publication, we agreed to post all of the peer reviewed chapters for easy download on the Forest Vegetation Management Conference website, noted Stewart. The Forest Vegetation Management Conference made major contributions to both the accumulation of the new knowledge that led to this book's creation and to the process that led to this book becoming a reality rather than just an idea.
Have you given your favorite tree a hug lately? Perhaps you would rather plant a tree? Well, on March 21, International Forest Day, Californians have a good excuse to do both.
In the first two decades of this new century, fire is having a transformative effect on California forests. Fires are burning with larger proportions of high severity and these high-severity patches are much larger, in many cases exponentially larger than would have occurred under natural fire regimes. This creates landscapes where all living trees – and potential seed sources for the next forest – have been killed. While fires can also have restorative effects and many species in California are adapted to fire, some species, like ponderosa pine, aren't adapted to these large, high-severity fire patches which alter the natural regeneration dynamics of the dry Sierran mixed conifer forests.
Across U.S. Forest Service lands in California, an average of 50,000 acres of forestland burned at high severity between the years 2000 and 2015; however, less than 30% of these acres were reforested on an average annual basis during this period. This creates a net cumulative loss of forest cover across public lands in the state.
To compound the complexity of this problem, there are growing instances of these large high-severity patches, burning again at high severity one to two decades later due to the homogeneity of vegetation and fuel profiles in the early seral stages after a fire. In 2013, the Rim Fire burned over 257,000 acres of largely mixed conifer forest, a notable portion of which had been replanted after the 1987 Stanislaus Complex Fire. Now foresters have to think: "Not only do we have to consider reforestation after a fire, but we must consider how we keep these young trees from burning up again!"
A common theme many ecologists agree on is that heterogeneous landscapes may be more resilient to fire – essentially breaking up the continuity of fuels and diversifying forest structure helps moderate fire behavior. However, over the past half century in California, we have tended to replant fires with a somewhat dense uniform square grid-spaced pattern of trees, which grow into a homogeneous carpet of new forest. As these trees grow, these dense plantations require maintenance – also referred to as “timber stand improvement” – activities to reduce competing shrub competition and “thin” the trees in order to maintain tree vigor and growth and reduce the fire hazard within the planted stand. Funding for timber stand improvement can wax and wane with the forest products market or federal budget priorities, and, on U.S. Forest Service lands, many of these plantations did not have follow-up treatment.
Seeing this problem brewing across the state, in 2005, a small sect of curious silviculturists and forest ecologists started asking some poignant question such as “Why do we spend money to plant trees which we will then spend time and money to remove a few years later – why don't we just plant less trees?” and “If heterogeneity is important for resilience, why do we always plant new trees in evenly spaced rows?” To many, this was, and still might be, heresy. But it begs a broader philosophical question that if we have diverse objectives for our forests, is it always appropriate to re-establish them in generally one uniform way? More importantly, given the latest fire trends, how can we promote heterogeneity and resilience to fire when we establish forests through planting?
I was one of these intrigued silviculturists. Linda Smith, culturist on the Plumas National Forest, and I started designing and planting low density, wide-spaced cluster plantations in 2007, after the 2006 Boulder Fire. The fire burned in a recreation area adjacent to a lake and part of our objective was to create a forest that would mimic a more naturally appearing structure, but we also knew this could be congruent with fire management objectives as well.
Ten years after the 2007 Moonlight Fire, much of the public lands were dominated by a homogenous fuel profile of flashy grasses, standing dead trees, a jack-strawed arrangement of fallen dead logs, and chest-high shrubs. While some of these stands had been planted, no site preparation or management of competing vegetation had been funded. We knew that any trees in this intermix would have a long haul competing against the shrubs, and in the meantime were exposed to high fuel-hazard each fire season.
Knowing something had to be done, the Plumas National Forest developed partnership agreements with the Sierra Nevada Conservancy and the Feather River Resource Conservation District to prepare the site, reforest and manage competing vegetation over approximately 3,000 acres. They also developed partnership agreements with Brandon Collins, a research scientist with both the U.S. Forest Service's Pacific Southwest Research Station and UC Berkeley Fire Science Laboratory, and Malcolm North, UC Davis associate professor of forest ecology, to monitor the success of different reforestation techniques at promoting heterogeneity and resilience to fire.
Through this partnership, we set up a replicated study to examine the effects of site preparation, planting, and competing vegetation treatments at promoting tree establishment and heterogeneity in young plantations.
First, the sites were selected, set up and pre-treatment fuel conditions were measured thanks largely to the leadership of Danny Foster and other graduate students in Scott Stephen's lab at UC Berkeley. Site preparation for planting occurred in the summer season of 2018 by using an excavator to pull and pile fuel accumulations of dead trees, downed logs and shrubs. These piles were then burned in the fall and winter to reduce fuel accumulations and prepare the site for planting. The following spring of 2019, sites were planted in equal densities, but in different arrangements, and with differing levels of competing vegetation control. Much of this work was facilitated by the hard work of Plumas National Forest silviculture staff members Maurice Huynh and Linda Smith and Feather River Resource Conservation District Manager Brad Graevs and his field crew. It is important to have great partners like these who truly understand the investment and value of monitoring management actions to inform adaptive management.
This spring will be the one year mark for the planted seedlings! There's still a bit longer to go before we're ready to reintroduce fire to the plantations, but we're on our way to that end goal.
In a sense, wildfire may have beat us out: Some of the wide-spaced cluster plantations that Linda and I planted in 2008 after the 2007 Antelope Fire burned 11 years later in the 2019 Walker Fire. I am pleased to see tree survival and some variable mortality. Looks like there will be some trees that deserve a hug this spring!
This winter, a generous amount of rain and snow has fallen on California, but it can't erase the brown swaths of dead and dying trees in the Sierra Nevada caused by five years of drought and decades of forest mismanagement.
Fire suppression and the harvest of the largest and most resilient trees in the forest led to a large population of weak trees. The prolonged drought further weakened the trees' defenses against native insects. Aerial detection surveys show that more than 102 million trees have died since 2010; more than 62 million died in 2016 alone. Public and private landowners are now struggling to recover from this natural disaster.
UC Cooperative Extension forester and natural resources advisor Susie Kocher recommends dead trees be removed and the landscape reevaluated.
“The dead trees will eventually fall,” Kocher said. “Removing trees around homes and other buildings is especially important for safety. Also, when they fall on the ground they become large fuels on the forest floor, leading to more intense fires.”
The cost of removing the trees can be substantial. The State of California is funneling disaster relief funds through California counties, utilities are felling trees that pose a threat to power lines, and local jurisdictions are removing trees that could fall on roads and other public infrastructure. However, most tree removal is the responsibility of private landowners.
When the dead trees are gone, before considering replanting, Kocher suggests Sierra residents carefully assess what has survived.
“There is often a lot of live vegetation remaining,” Kocher said. “Make a map and mark where you find living trees and shrubs and identify them by species and size. If you have a significant number of trees left, you may not need to replant.”
Kocher suggests nurturing the remaining young trees.
“You may want to thin trees out so that available sun and soil moisture are focused on the healthiest individuals. Some watering in the summer may help counter stress caused by increased solar radiation,” she said.
If removing the dead trees leaves the landscape too bare, replanting native conifers is a good strategy. Conifers include pine, cedar and fir trees, but in California's dense forests, firs and cedars – which do well in shady conditions – are beginning to dominate. Replanting may be a time to give native pines – such as Jeffrey, ponderosa and sugar pines – a chance to recover ground.
“The fact that many pines have died does not necessarily mean they are no longer adapted to your location, even with our warming climate,” Kocher said. “There may be a few locations that are less suitable for trees that have grown there in the past, but for most areas, local growing conditions should support native conifers in the near future.”
Native plants and shrubs that died during the drought or were damaged during tree removal will likely come back on their own without replanting. Shrubs and oaks can re-sprout and native herbaceous plants generally store seed in the soil that will grow under native rainfall conditions.
Replanting of trees also gives landowners the chance to shape the landscape for best effect. Kocher offers the following recommendations on replanting trees in natural landscapes:
Space trees at least 10 feet apart.
Trees and flammable vegetation should be kept at least 10 feet away from the home, planted sparsely within 30 feet of the home and spaced widely enough in the 30 to 100-food zone so the crowns of the trees will not touch when they are mature. Beyond 100 feet, trees can fill into a more natural looking forest.
Plant trees at least 10 feet from power lines.
Do not plant trees within the road right of way to prevent interference with snow clearance, maintenance and construction projects.
Plant pines where there is a lot of sun. Do not plant sugar pine on the driest sites.
Avoid planting where the mature trees will block desired views.