- Author: Kat Kerlin
Reposted from the UC Davis College of Agricultural and Environmental Sciences news
Redwood Trees Have 2 Types of Leaves, and They Do Totally Different Things
- Redwoods have two types of leaves, one to make food and the other to absorb water
- Study is first to estimate whole-crown water absorption in a large, mature tree
- Leaf types shift places on the tree depending on if environment is wet or dry
- Findings can help scientists monitor trees' adaptability amid a changing climate
Redwoods are among the most well-studied trees on the planet, and yet their mysteries continue to surprise and delight scientists and nature lovers.
Scientists from the University of California, Davis, discovered that redwood trees have two types of leaves, and those leaves have completely different jobs, according to a study in the American Journal of Botany. Together, these functionally distinct leaves allow the world's tallest trees to thrive in both wet and dry parts of their range in California, without sacrificing water or food.
Division of labor
The peripheral leaf spends its working hours making the tree's food — converting sunlight into sugar through photosynthesis. Its colleague, the axial leaf, does almost nothing to help with photosynthesis. Instead its specialty is to absorb water. In fact, the study found that a large redwood can absorb up to 14 gallons of water in just the first hour its leaves are wet.
How does that compare to other trees? Scientists don't know. This is the first study estimating whole-crown water absorption in a large, mature tree. Because large redwoods have over 100 million leaves, this absorption record may prove hard to beat.
In wet forests, photosynthesis can be inhibited by films of water covering leaf stomata when they get wet. For redwoods, the different leaf types allow the trees to get wet and still be able to photosynthesize. The peripheral leaves have a waxy coating that slows water absorption but may help them continue photosynthesis throughout the wet season.
“I'd be surprised if there weren't a lot of conifers doing this,” said lead author Alana Chin, a Ph.D. student in ecology with the UC Davis Department of Plant Sciences at the time of the study. “Having leaves that aren't for photosynthesis is in itself surprising. If you're a tree, you don't want to have a leaf that's not photosynthesizing unless there's a very good reason for it.”
The study also found that leaves can shift their “office space” along the tree depending on whether the environment is wet or dry.
In the wet, rainy north coast, the water-absorbing leaf type is found on the tree's lower branches, leaving the upper, sunnier levels to the photosynthesizing leaf type. That dynamic flips for redwoods in their southern range: The water-collectors live among the tree's higher levels to take more advantage of fog and rain, which occur less often in the drier environment.
To arrive at their findings, the authors collected shoot clusters from six redwood trees at five forest locations stretching from wet Del Norte County to the dry Santa Cruz Mountains and exposed them to experimental fog. They estimated the water absorption potential for seven additional trees — including the tallest living tree — and took samples at varying heights.
They then compared the anatomy and measured photosynthesis of the peripheral and axial leaves to understand their function. They also developed a physics-based causal model that allowed them to determine the leaf traits that regulate absorption rates.
Amid all the findings, Chin is most excited to have found an easy and effective way to indicate redwood trees' ability to access fog. Researchers can monitor how and if redwoods are adapting to climate conditions and a future, drier world by simply looking at the visible waxes covering the two types of leaves — something that could be captured on a cell phone camera and shared by other scientists or even members of the public.
Redwoods are renowned for their resilience in the face of many natural threats and inspire numerous superlatives: They are among the planet's biggest, tallest, oldest trees. They have tannin-rich heartwood, fire-resistant bark and pest-resistant leaves. This new finding is another example of their ability to respond to environmental conditions, like drought and water stress.
“The cool thing here is their ability to thrive under all these circumstances and adjust themselves to these different environments,” said Chin, who grew up near the redwoods in Mendocino County. “That things like this can be happening right under our nose in one of the best-studied species out there — none of us assumed this would be the story.”
Study co-authors include Paula Guzman-Delgado, Jessica Orozco, Zane Moore and senior author Maciej Zwieniecki of the UC Davis Department of Plant Sciences, as well as Stephen Sillett, Lucy Kerhoulas and Marty Reed of Cal Poly Humboldt, and Russell Kramer of Dipper and Spruce LLC in Washington.
The study was funded by the National Science Foundation and a Katherine Esau Fellowship from UC Davis.
- Alana Chin, UC Davis Plant Sciences, firstname.lastname@example.org. Chin is currently based in Switzerland. (Please note time difference for interview requests.)
- Kat Kerlin, UC Davis News and Media Relations, 530-750-9195, email@example.com
- Author: Denise Godbout-Avant
People often rake their leaves and put them out to be picked up as trash. I have always preferred to leave the leaves for my garden.
If you take a walk in a forest, you'll see leaf layers several inches deep around trees and bushes. Fallen leaves have a complex relationship with trees and nature, providing many benefits which can be reproduced to some extent in our gardens.
Fallen leaves have the same weed suppression and moisture retention properties of shredded wood mulch—and they're free! Where mulch is desired as a decorative element, what could be more seasonally appropriate than a pile of brightly colored fall leaves? This natural mulch also provides insulating winter cover from cold temperatures for roots, seeds, and bulbs.
A Web of Life in Leaf Litter
Leaf litter isn't just free fertilizer and mulch. It provides food and shelter for a wide variety of living things including spiders, snails, worms, beetles, millipedes, mites, toads, frogs and more—these in turn support mammals, birds, reptiles, and amphibians that rely on these creatures for food.
Detritivores (organisms that eat dead or decaying plants or animals) break up and excrete leaf litter. Fungi and bacteria then take over and complete the recycling process converting these smaller pieces into nutrients which then sustain neighboring plants. They in turn help support biodiversity by becoming food themselves.
Numerous bird species such as robins and towhees forage in the leaf layer searching for insects and other invertebrates to eat.
Raking up leaves and putting them in the trash could have the unintended consequence of removing some of next year's garden butterflies and moths, many of which are pollinators. Most butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, they often use leaf litter for winter cover. Fritillaries and wooly bear caterpillars will tuck themselves into a pile of leaves for protection from cold weather and predators. Some Hairstreaks lay their eggs on fallen oak leaves, which become the first food of the caterpillars when they emerge. Swallowtail butterflies disguise their cocoons and chrysalises as dried leaves, blending in with the “real” leaves.
Bumble bees also rely on leaf litter for protection. At the end of summer, mated queen bumble bees burrow an inch or two into the earth to hibernate for winter. An extra thick layer of leaves is welcome protection from the elements.
All of which makes leaf litter an integral part of a complex web of life.
What You Can Do
Composting leaves is a terrific way to recycle and create a nutrient-rich garden soil amendment at the same time. Some gardeners opt for shredding their fall leaves for use in compost piles. Like people who mulch their lawn leaves with a mower, consider leaving some leaves undisturbed in garden beds and lawn edges. If space allows, you could create a leaf pile, allowing it to break down naturally, or add the leaves gradually to your compost pile over time. Such efforts will keep leaf litter critters safe and allow you to benefit from the rich garden gift that falls from the trees above.
While it is ideal to “leave the leaves” permanently—for the benefits mentioned above—if you do decide you need to clean your garden and remove the leaves in spring, try to wait until later in the season, so as to give the critters that have been protected by fallen leaves over the winter time to emerge and depart.
Some gardeners may be concerned that autumn leaves, matted down by rain or snow, could have a negative impact on their perennials. However, a thick layer of leaves provides additional insulation against chilly weather and protects newly planted perennials from frost which could damage tender roots and shoots. Anyone who has spotted fragile spring seedlings popping up in the woods knows that all but the most fragile of plants will erupt through the leaf litter in spring without trouble.
So, leave the leaves. While you can't perfectly emulate a forest, your garden will be healthier and more diversified, you'll help support a vast array of wildlife, and you'll reduce the strain on landfills.
Denise Godbout-Avant has been a UCCE Stanislaus County Master Gardener since July 2020./h3>/h3>/h3>
- Author: Heidi Aufdermaur
Have you ever had a hobby that turned into an obsession? One of my hobbies is gardening of course, as a Master Gardener. Not too long ago, I acquired a chipper/shredder. One of my gardener friends had two and sold one of them to me at a fair price. I have always wanted one, dreaming of all the rich mulch I could make with my own waste.
I was excited to use it for the first time, donned the earplugs and safety glasses and got busy. Of course, I had to first collect the yard waste. I started coveting all the potential material that I thought would be suitable to shred or chip. I collected from my yard first, then one morning on the daily walk with my husband and soon after Christmas, I had a new insight for all the Christmas trees that were being discarded on the streets. I commented to my husband about collecting some of them to chip. To my surprise, I came home one day from running errands and found about 6 Christmas trees piled up in our yard. My heart fluttered with excitement. I was worried that adding too many of the pines would change the pH of my soil so I consulted Ed Perry, our former Environmental Horticulture Advisor for Stanislaus County. He said I could compost and chip away, as I was adding other species to the mix and it would take a lot more pine trees to make any difference in the pH of my soil.
I started seeing all the shrubs and trees in our yard that needed a good trim and piled them up to dry for a while. I also added some spent flowers to the pile. What I learned about shredding flowers is to cut off the seed heads (if I didn't want them to germinate where I spread the final product). I learned that after I had shredded some old marigold plants, spread the mulch in a pathway between my vegetable rows, I soon had marigolds sprouting up all over. I transplanted a few, left a few and pulled the rest, adding them to the new pile before they flowered.
I began to explore the surrounding yards in our neighborhood. Leaves and clippings looked like gold to me. My neighbor was extremely happy to let me rake her lawn of all the beautiful leaves that had fallen. To say the least, I have become somewhat obsessed with this new habit of gardening. I am also pleased that I am not adding all this waste to the green can for a trip to the land fill.
Did you know there is an assembly bill (AB341) that requires communities to divert yard waste from landfills and recycle it? With the rapidly depleting landfill capacity in California, 75% of yard waste is to be recycled. This goal was to be achieved by 2020. This bill requires every commercial business, institution, and apartment building to implement recycling programs.
Even though this bill focuses on businesses and large complexes, it's also good practice for homeowners. Keeping your yard waste on site, adding it to a compost pile or breaking it down by running over small portions with a lawn mower, one can keep this valuable commodity in one's own yard. Some benefits of mulch include reducing water loss to evaporation, moderates soil temperature, reduces weed growth thus making weeds easier to manage and reduces dust in drip-irrigated landscapes.
So, if you become obsessed like me, just think of all the good that happens when collecting your yard waste and keeping it on site. Happy Gardening.
- Author: Ed Perry
If you're interested in making your own compost, the perfect time to start is in fall. A light covering of leaves on the surface of your lawn can simply be shredded with your lawn mower and left in place. They will decompose rapidly and add valuable nitrogen and organic matter to the soil. Once the leaf layer becomes too thick, you must begin raking them up for your compost pile.
Some gardeners simply pile the leaves in one place and allow the composting process to proceed slowly. However, if you want finished compost quickly, you'll want to use the “rapid” or “hot” composting method. Rapid or hot compost is made by manipulating the decay process, which is done by balancing food, water and air in the compost pile to favor the growth of high temperature microorganisms. A byproduct of their activity is heat.
To construct a hot compost pile, you will need a combination of bulking materials and energy materials. Bulking materials, sometimes called “brown materials,” are dry, porous resources such as sawdust, wood chips or straw. They help aerate the compost pile but are too low in moisture and nutrients to decay quickly on their own.
Energy materials, sometimes called “green materials,” include grass clippings, fresh animal manures, fruit and vegetable waste and garden trimmings. These materials provide the nitrogen and carbon compounds needed for fast microbial growth. If piled without bulking materials, energy materials are too wet and dense to allow adequate air into the compost pile. Such materials may emit a rotten egg smell as they decompose.
To build a rapid compost pile, combine two parts by volume bulking materials with one part energy materials. Some other hints for a rapid compost pile include:
- Chop your raw materials into small pieces. For best rapid composting, the particles should be from 1/8 to 1/2 inch in diameter.
- Mix the types of raw materials, rather than layering them.
- A large pile holds heat better than a small pile; for rapid composting, make the initial pile at least a cubic yard (36” X 36” X 36”) in volume.
- Keep the pile moist, but not wet.
- Turn the pile once a week to aerate it.
The raw materials that you use in composting have their own microorganisms. There is no need to add starters or soil. If the rapid process is working properly, you can have ready to use compost in as short a time as 3 weeks. Even if it doesn't work that fast, you will still eventually have a valuable compost that you can use to enrich your garden soil.
Still have questions about composting?
Sign up for our Composting Basics class!
When: November 24, 2020 6-7:30 p.m. PST.
Where: on Zoom.
How: http://ucanr.edu/compost/2020 sign up by Nov 24 at 4 p.m. to receive a link sent the morning of the class.
Instructors: Master Gardeners Terry Pellegrini and Heidi Aufdermaur.
And remember, all classes are recorded so you can always watch it again later.
Hope to see you there!
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
- Author: Denise Godbout-Avant
Why do some trees change color and drop their leaves before winter? And why are there different colors?
Leaves are colored by pigment molecules. Most leaves appear green because they contain an abundance of the pigment chlorophyll. Chlorophyll is the site of photosynthesis where the sun's energy is converted into the carbohydrates that are plants' food source. During the cold winter months when there is less sunlight, it would take too much energy for some trees to keep their leaves healthy. So deciduous trees lose their leaves for the winter. Evergreen trees have a different strategy for dealing with winter's challenges (which is a topic for another time!).
Elevation, latitude and weather all affect the timing and intensity of fall colors. Higher elevations and northern latitudes produce earlier autumn colors in trees. In general, autumn weather with lots of sunny days, dry weather, and cold, frostless nights will produce the most vibrant palette of fall colors. Some trees that can produce vivid colors include maples, gingkos, aspen, birches, Japanese maples, liquidamber, cherry, redbud, Chinese pistache, and dogwood.
In the Central Valley we usually don't get the glorious colors like the Sierra Mountains or the east coast, but we do get some color which usually starts in early November. So, enjoy the autumn jewels since it occurs only for a brief period each fall!
Denise Godbout-Avant has been a UCCE Stanislaus County Master Gardener since July 2020.