Leader for today’s Ramble: Kathy Stege
Authors of today’s Ramble report: Linda Chafin, Don Hunter
The photos that appear in this report, unless otherwise credited, were taken by Don Hunter. Photos may be enlarged by clicking them with a mouse or tapping on your screen. Not all of Don’s photos from today’s ramble made it into the ramble report, so be sure to check out his Facebook album at this link.
Nature Ramble rainy day policy: We show up at 9:00am, rain or shine. If it’s raining, we will meet and socialize in the conservatory (bring your own coffee); if there is a break in the rain, we’ll go outside and do a little rambling.
Number of Ramblers today: 31
Today’s emphasis: Soils and roots in the Georgia Piedmont
Announcements:
Andrea Fischer, Volunteer Coordinator for the Botanical Garden, asked Ramblers to volunteer their expertise at the welcome desk in the Visitor Center. With Ramblers’ extensive familiarity with all areas of the Garden, she knows we would be good candidates to fill this need. She’s not looking for a long term commitment, but will contact willing volunteers as needed to fill shifts for regularly scheduled volunteers who can’t make their shifts. Contact Andrea at afischer@uga.edu or let Linda know if you are interested.
Interesting articles:
“Is it too late to save the southern grasslands?” A nice piece by Margaret Renkl.
Another reason to save the Amazonian rain forests — chocolate!
Ferns and flowers bribe helpful ant defenders with nectar, but ferns developed this ability much later. Click here for more.
Show-and-tell:
Kathy brought roots of two species, Pokeberry (above) and Daikon Radish (below), both known as “sod busters” that break up hard-packed clay soils and nearly impenetrable soil layers known as “plow pans.” Roger C. shared that plow pans are created by repeated plowing at the same depth year after year with a bottom or turning plow, and added that it’s necessary to get out a subsoiler every decade or so to break up the plow pan. Unless they are broken up, hard pans will prevent rain from penetrating the depths of the soil, hasten moisture evaporation from the soil, limit soil aeration, and stunt roots. Like most of Clarke County, Kathy’s property was once in cotton agriculture. Over time, both Pokeberry’s and Daikon’s roots break up compacted soil and plow pans and also increase the carbon content of the soil. Kathy has found, through experimentation with both, that Pokeberry roots do a much better job than the radish. She even “torments” her plants to encourage them to develop larger tap roots and lateral roots of varying sizes. Daikon Radish, on the other hand, had much shorter underground parts (the pale pink section) and compacted growth layers near the tip from difficulty penetrating the soil.
Today’s Reading: Kathy read from “The Revolutionary Genius of Plants, A New Understanding of Plant Intelligence and Behavior” by Stefano Mancusco.
From p. 77 - “[The root system] is a physical network whose apexes form a continuously advancing front; a front composed of innumerable tiny command centers, each of which supplements the information gathered during the development of the root and decides the direction of growth. Thus the entire root system guides the plant like a sort of collective brain, or better still, a distributed intelligence on a surface that can be huge. While it grows and develops, each root acquires information essential to the nutrition and survival of the plant. This advancing front can reach a really impressive size. A single rye plant is capable of developing hundreds of millions of root apexes. This is an extraordinary fact, yet negligible when compared to the root system of an adult tree. We do not have reliable data about the roots of trees, but certainly we are talking about several billion roots. We know that there can be more than a thousand root apexes in a single cubic centimeter of forest soil, but we do not have any realistic estimates of how many root apexes an adult tree might have in its natural environment.”
From p. 80 – “A few years ago, my colleague Frantisek Baluska, decided to study roots as a collective organism, seeing them as being like a flock of birds or a colony of ants. This approach proved to be very effective, confirming that the structure of a plant’s root system and the way it explores the terrain and uses resources can be described with great precision using swarm behavior patterns, such as those used in the study of social insects. Navigating along a tiny gradient is an almost impossible task for a single ant; any local variation in the gradient would cause it to get lost without the possibility of finding its way back. In contrast, by acting collectively, a colony can easily overcome this obstacle because it operates like a large integrated matrix of sensors that continuously processes the information received from the environment.”
Kathy shared how moved she was, while preparing for today’s Nature Ramble, by the concept of roots as sentient structures, taking on the task of providing nutrition, as well as providing structural support, for the trees. She briefly addressed the concept of communication between trees, and stressed that the most important factor controlling tree growth and root development is the role of mycorrhizae, extensive networks of fungal “roots” that distribute nutrients and information between trees, among other tasks. Mycorrhizae may even be responsible for monitoring the health of individual trees and deciding, if one is found to be dying, to cut off that tree’s lifeline in order to direct nutrients where they would be the most beneficial.
Today’s Route: We took the paved path through the Lower Shade Garden to the trail that ends at the Orange Trail Spur and out into the right-of-way. We made our way to the river overlook at the south end of the ADA path and returned to the Porcelain and Decorative Arts Museum for some air-conditioned socializing and a fabulous array of snacks, provided by Kathy.
Today’s Observations:
Kathy introduced today’s topic by sharing her experiments with permaculture and native plants in her garden, near Sandy Creek Park. She became interested in soils as a result of her efforts to improve the soil on her property. Compared to many areas in the Botanical Garden that have good quality soils, her property has all the ills familiar to Piedmont gardeners: heavy clay subsoil from which the top soil has long since washed to the rivers and the Atlantic Ocean; a plow layer hardpan; and low fertility.
Kathy discovered many places at the Botanical Garden with silty or sandy loam soils and, thanks to underlying amphibolite bedrock, high levels of key nutrients such as calcium and magnesium. The soil in some of the natural areas of the Botanical Garden have 22 times the level of calcium in her home garden.
Kathy stopped at a point on the White Trail below the Children’s Garden Forest Play Area and raked back the chipped hardwood mulch layer along the edge of the trail. The chips have broken down into what amounts to a highly organic potting medium, but it lacks the nutrients and minerals essential for plant growth. This material was likely sourced from UGA’s Bio-conversion Center, near the Garden at 1155 East Whitehall Road.
Jason Young, the Garden’s Director of Horticulture says, “We have 2 different ‘bins’ for woody material and herbaceous material—one is a dump truck and the other a dump trailer. We move that material to the Bioconversion Center on a weekly basis. We receive materials back from the facility also. In the spring and fall, we bring in numerous dump truck loads of compost and mulch to amend beds and cover bare ground, respectively.”
Kathy is separating the litter layer and the duff layer from the underlying mineral soil which is filled with roots of all sizes.
The litter layer is the top layer of the forest soil and consists of recognizable plant parts, such as leaves, nuts, and small twigs. Duff is the partly decomposed layer of organic matter beneath the litter layer and above mineral soil.
“The organic duff and litter layers play critical physical, chemical, and microbiological roles in forest ecosystems… Duff contains many ectomycorrhizal fungi that have symbiotic relationships with tree and shrub roots; these partnerships aid in the uptake of water and certain nutrients and may protect the surrounding soil structure and protect against other soil-borne organisms…Duff and litter protect the soil from erosion and compaction and form a mulch for maintaining soil moisture… The forest floor is critical for nutrient cycling…and many nutrients—including nitrogen, phosphorus, calcium, magnesium, and potassium—are stored for release during decay or burning of duff and litter… Duff and litter are also important for carbon sequestration. Chojnacky, Amacher, and Gavazzi. 2009. Separating Duff and Litter for Improved Mass and Carbon Estimates. Southern Journal of Applied Forestry 33(1):29-34.
Larger roots in a tree’s root system may extend far beyond the edge of the crown or the drip line, as it is usually called. In dense forests, the root system will be less extensive than in less dense woodlands. When trees die or are removed, the dead and dying roots will continue to contribute to forest health, adding carbon to the soil, storing moisture, and fostering the growth of mycorrhizae.
Kathy pointed out that near the base of the slope the soil is a sandy loam rich in nutrients and organic matter that have moved downslope. Even in this rich environment, most of the roots are limited to a shallow root zone.
There are two common misconceptions about tree roots: first, that all trees have deep tap roots, and, second, that the root system of a tree is a mirror image of its crown. In fact, few trees have tap roots once they grow out of the seedling stage. Lateral roots provide all the necessary support and access to moisture and nutrients that are not available deep in the subsoil. Tree root systems do not reflect the shape of their crowns. A better image is that of a wine glass resting on a plate, with the plate representing the depth and extent of the roots. Root systems are believed to be about 50% wider than the crown.
Floodplain soils are very different from those we see on slopes and ridges. Kathy dug a pit to show us the depth of the sandy loam that has accumulated over the decades from a combination of flood deposits and downslope erosion bringing sediments.
Kathy dug up the roots of a Yellow Crownbeard growing in the floodplain (left) and compared them with the roots of the same species dug from her property (right).
The Ramble ended at the Middle Oconee River, which is showing signs of the severe weather we’ve had for the last six weeks, at least. According to the National Weather Service, there were 2.09 inches or rain in Athens in June, when the average is 4.9 inches for June. The average temperature in June was 79.4 degrees, compared with the 1991-2020 average of 77.7 degrees. In July, we’ve had about 1.5 inches of rain, with none since July 8. The average rainfall for July, 1991-2020, was 4.2 inches. This week is forecast to bring some relief!
At this point, Ramblers made their way to the Porcelain Museum, where Kathy had laid out an amazing spread of breakfast, brunch, and lunch goodies. Never short of something to talk about, we gathered around tables, eating and socializing for the next hour. Many thanks to the Botanical Garden for making this space available to the Ramblers during this hot weather!
Post-Ramble Observations:
Genista Broom Moth caterpillar on Wild Indigo leaves near the elevator in the Visitor’s Center Plaza
Eastern Tiger Swallowtail butterfly nectaring on the last of the Bottlebrush Buckeye flowers near the elevator
Two-spotted Longhorn Bee nectar-robbing from the base of a Pink Tropical Sage flower; this is a cultivar of the red-flowered native of the coastal plain, Scarlet Sage.
Castor Bean in colorful fruit in the bed at the Garden’s entrance
SUMMARY OF OBSERVED SPECIES
Yellow Crownbeard Verbesina occidentalis
Genista Broom Moth (caterpillar) Uresiphita reversalis
Wild Indigo Baptisia sp.
Two-spotted Longhorn Bee Melissodes bimaculatus
Pink Tropical Sage Salvia coccinea cultivar
Eastern Tiger Swallowtail butterfly Papilio glaucus
Bottlebrush Buckeye Aesculus parviflora
Castor Bean Ricinus communis