- Author: Jeannette Warnert
Reposted from the UCANR News
In 2020, 9,000 fires scorched more than 4 million acres of California, a record-breaking year, reported Alejandra Borunda in National Geographic. Fires burned through homes and oak forests, grasslands and pines — and also through patches of giant sequoias and coast redwoods, respectively the most massive and the tallest trees on earth.
Giant sequoias are not the oldest living trees, but some have been growing in Sierra Nevada forests for more than 3,200 years. They are found in 68 groves on the Sierra's western flank. The state's redwood forests grow in a narrow strip along the coast of Northern California and Southern Oregon.
The 2020 fires burned through about 16,000 acres of sequoia groves, about a third of their total area. In redwood forests of the Santa Cruz Mountains, 40,000 acres burned.
But because redwoods are well-adapted to fire, they'll likely recover pretty quickly, said Scott Stephens, a UC Berkeley fire scientist. “In some ways, this fire could make redwoods more dominant in the landscape," he said, because other trees — like the hardwoods or Douglas firs that crowded the local forests — died outright in the burns.
However, scientists are concerned one cause of the fires, climate change, could have additional impacts on these natural treasures.
Since the mid-1800s, temperatures in the western U.S. have increased by 1.6 degrees Fahrenheit. Fog banks are fading in coast redwood territory, and snows are less consistent in the Sierras. The changes leave redwoods and sequoias without their preferred climate conditions.
The most responsible thing to do now, Stephens said, is to “take the opportunity that has been handed to us,” and make a plan to go back in and burn again—soon, within the next few years.
UC Cooperative Extension forestry advisor Lenya Quinn-Davidson agrees that California must manage fire to help the trees survive. Tree-ring records show that humans have influenced the fire regime for better and worse as long as they've been in these forests.
“The empowering message there is, human management can actually override the effects of climate in a fire contest,” Quinn-Davidson said. “It's not just a climate story. We can't just throw in the towel, feel overwhelmed, and tell ourselves these trees are done for. That's not true!”
- Author: Robert Sanders
Reposted from UC Berkeley News
Todd Dawson's field equipment always includes ropes and ascenders, which he and his team use to climb hundreds of feet into the canopies of the world's largest trees, California's redwoods.
It's laborious work, but he'll soon be getting a little help. From drones.
The need is urgent, Dawson said. Since 2010, more than 102 million trees, mostly pines and firs, have died in California because of drought, 62 million in 2016 alone. Why are pines and firs succumbing, but the thousand-year-old sequoias surviving, and will that continue into the future?
In August, he and Gregory Crutsinger, a plant ecologist and head of scientific programs at Parrot, performed the first test of a drone, a quadcopter, equipped with a state-of-the-art multispectral camera that takes photos in red, green and two infrared bands. Called the Sequoia, the camera works like more expensive satellite and airborne sensors, measuring the sunlight reflected by vegetation in order to assess physiological activity or plant health.
“Before, a team of five to seven people would climb and spend a week or more in one tree mapping it all around,” Dawson said. “With a drone, we could do that with a two-minute flight. We can map the leaf area by circling the tree, then do some camera work inside the canopy, and we have the whole tree in a day.”
After the data and photos were stitched together by a software program called Pix4D, Dawson and Crutsinger ended up with a three-dimensional representation of the foliage that his team had never seen before – information that will be used to determine how much carbon the tree takes up each day and how much water it uses, the basis for assessing what might happen with higher carbon dioxide levels in the atmosphere and less water on and in the ground.
“With repeat flights you can watch a forest grow without ever actually measuring any trees in the forest,” Dawson said. “I think drone technology holds a lot of promise to do some very innovative science over time and in three-dimensional space with a relatively cheap tool. It is really pretty amazing.”
Monitoring the health of the state's iconic sequoias is just one instance of how drones, combined with state-of-the-art sensors, can benefit science, Crutsinger said.
“Drone technology is getting much cheaper, but stitching and photogrammetry are innovating at the same time,” he said, referring to the science of making measurements from photos. “That is the backbone of the whole new commercial drone industry: not just the ability to capture the data, but also to process very high-resolution photos into millions of points that generate a three-dimensional model. This is going to help science but also environmental monitoring, agriculture and even construction sites.”
Crutsinger, a former Miller postdoctoral fellow at UC Berkeley, is asking other scientists to propose research collaborations with Parrot in exchange for free drones, cameras and analysis software. These Climate Innovation Grants are open to any student or researcher around the world.
Monitoring a changing environment
Dawson is now assessing how best to use the initial data and the drone and camera to answer questions in plant ecology. For the giant sequoias (Sequoiadendron giganteum), which he studies in the University of California's 320-acre Whitaker Forest just outside Sequoia-Kings Canyon National Park, he anticipates learning a lot more about their physiology than can be achieved by roping onto the canopy. Knowing the leaf area alone is a key advance, since he and his team have been able to model only the trees' branches and twigs, from which they estimate leaf surface.
“If we know how much area is there, I can tell you how many tons of carbon per meter squared per day was fixed by that forest, and how much water was used by that leaf area per day. You can start to get at rates of carbon exchanged between the tree and the atmosphere and then at rates of carbon sequestration,” he said. “These are important numbers for our forecasting models, so we can say, ‘If the climate goes up by 2 degrees, or it gets drier by 10 percent, what the hell is going to happen to that productivity?' All of a sudden you have power to really measure the pulse of the Earth, which is a really hard thing to do at large scales.”
Dawson is keen to see how drones and specialized sensors can aid his other research, which involves not only giant sequoias but also coastal redwoods, California's oaks and the canopy epiphytes in the clouds forest of Costa Rica. But he also sees a wealth of other possibilities.
“I think this is one of the tools for ‘change detection' that we are going to find is a game changer,” he said. “We can do this quickly and accurately over natural lands and agricultural lands and forest that burned and places that were hit by hurricanes or droughts, and look at the changes taking place and why they are taking place much more easily than we did before.”
Dawson doesn't plan to give up climbing trees, though. Some data will still need to be captured in the tree tops, if only to connect drone observations with tree physiology and ecology.
“The low-hanging fruit right now is really, what basic-level things that take up a lot of time can we replace with the drone, and what do we still need to do with boots on the ground in the field,” Crutsinger said. “If we can just save time and person power, that is most of the cost of doing scientific research, particularly in ecology. We are looking to augment what already happens on the ground — or in this case the crown — and then think about what new questions we can ask as well.”
The vast majority of trees have roots that interact with below-ground fungi, together forming a 2-species complex known as mycorrhizae. In our study, which was recently published in the journal, Mycologia, we looked at the way roots of giant sequoia seedlings formed mychorrhizae relationships and how that influenced the growth of giant sequoia seedlings. Learning about how giant sequoia seedlings grow is particularly important since seedling establishment in giant sequoia has been below what is needed for long-term sustainability. We found that when we planted giant sequoia seedlings, beneficial fungi would attach on to the seedling’s roots mainly when the seedlings were planted in open sunny conditions. While it was hypothesized that the fungi would not be as common on roots in areas that had been burned, there was no difference between burned and unburned locations. Also interestingly, the beneficial fungi actually seemed to outcompete harmful fungi, thus possibly helping seedlings to avoid other diseases. This mycorrizal interaction between tree and fungus is a potentially important requirement for giant sequoia to grow fast as a seedling, and may be a key ingredient in how it eventually becomes the world’s largest organism.
The triple crown of resources: Light, water, and nutrients
Nature is dominated by individualistic, chaotic, and brutal selfishness. Organisms are hard wired to have a primary goal- to reproduce. Often, plants achieve this goal at the expense of other organisms via a fierce competition for the triple-crown of resources: light, water, and nutrients (it’s a baseball theme today). But sometimes it is in an organism’s best interest to be of assistance to another. Such is the case with mycorrhizae, which is a combination of plant roots and fungi attached to each other (“myco” = fungi; “rhizae” = roots).
Giant sequoia is an interesting species because it is so different than any other in so many ways. The most obvious difference that people know about is its tremendous size- larger than any other tree on earth. But the way that it reaches this size, and in fact its entire “life history strategy” is somewhat of an outlier when you compare it to other tree species. All trees form mychorrhizae, but the way in giant sequoia forms this relationship with fungi also appears to be an outlier. It forms what are known as “arbuscular mycorrizae,” which is uncommon in conifer trees. Beyond that, not much is known about this plant-fungus interaction in giant sequoia, but this study offers some insight.
The primary relevance to landowners and stakeholders might be that this research reminds us that planting a tree and getting it to survive and grow is a complex, ecological process. It is important to understand how planted seedlings survive and grow because planting is something we might be doing a lot more of in forests, as climate change and wildfires become forces that hinder natural regeneration across larger and larger areas. Successfully planting a tree, where the measure of success is getting the tree to complete its life cycle (i.e. to reproduce), involves much more than planting a tree and walking away. It involves understanding the resource requirements for that species, and how that particular tree will be able to make its way up into the canopy to become mature. For giant sequoia, and most other trees, the mutualistic interaction that seedlings will have with root colonizing fungi is key information. This study suggests that planted giant sequoia seedlings have the best chance of success when they are placed in distinct canopy openings in sunny conditions, in part because this is where the mutualistic relationship with fungi can benefit giant sequoia most by helping it to grow quickly into the tall canopy above.
By the way, I think most green campaigns that ask you to pay a little extra so that you can sponsor the planting of tree seedings are scams. I would not advise believing or certainly not paying for such “plant-a-tree campaigns” unless you know the species that is being planted, the location, and the method to be used for tracking survival.
Imagine that giant sequoia is a base runner, where rounding third means going home, which in terms of a tree is equivalent to reaching the canopy and reproducing (and for a person on a date, this is of course equivalent to something similar).
The fungus that forms the mycorrhizae is the third-base coach, hoping to be of some assistance to the base runner but hoping to get something in return (a job).
A base runner doesn’t really need the third base coach, but the third base coach definitely needs the base runner to have a job and make a living. Often the third base coach can be helpful to the runner, but only when things are already going pretty well for the runner. When they are rounding third base, the runner is in pretty good position to score, and the third base coach can help them score. Sometimes, however, the third base can be a hindrance if they get in the way or if they give the runner some bad advice. But usually they are a help. And of course no championship team (such as the Giants) would be without a third base coach.
Get it? Giant sequoia seedlings are happy to have this relationship with fungi, but only when things are already going well. Mycorrhizae were more common on seedlings when they were planted in the open, so there was plenty of carbon for the seedling to spare. It is carbon that is the currency paid by the tree, in return for nutrients like Phosphorous from the fungus. And fungus can also keep the plant out of trouble by fighting off pathogenic fungi, kind of how a third base coach can tell the runner to get back when the pitcher tries to pick them off.
Implications? If you plant giant sequoia, do so in distinct canopy openings and pay attention to how the nursery either sterilized or inoculated the soil. In this case, the nursery had sterilized the soil so the mycorrhizae developed on roots after the seedlings were planted in the field. When you plant far away from a mature forest edge, don’t worry about it taking a long time for fungus to colonize the area- they are probably already there because of lateral roots from surrounding trees.
Fahey, C, RA York, and TE Pawlowska. 2012. Arbuscular mycorrhizal colonization of giant sequoia (Sequoiadendron giganteum) in response to restoration practices. Mycologia 104(4):988-997.
- Author: Jaime Adler
Re-posted from UC Berkeley Department of Environmental Science, Policy, and Management.
This image from a Nelder Plot at Blodgett Forest Research Station in the Sierra Nevada mountains is part of a study designed to find out how trees respond to different levels of competition for resources (light, water, and nutrients). The wagon-wheel pattern provides a space-efficient way to experimentally increase tree density as one gets closer to the center of the “spokes.”
The trees in the image are giant sequoia, a species that is particularly sensitive to competition. After only a few years, one can see from the image that trees near the center of the spokes are smaller than trees near the edges where tree density is low.
The study has implications for how foresters manage tree density, depending on various objectives such as wildlife habitat, timber, or carbon sequestration.