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Posts Tagged: soil
The Soil Microbiome
It promises to be an outstanding seminar.
André Custodio Franco, assistant professor, Indiana University, Bloomington, will speak on "Deciphering the Soil Macrobiome: Belowground Communities Driving Ecosystem Responses to Global Change" at a seminar hosted Monday, Nov. 18 by the UC Davis Department of Entomology and Nematology.
It's set or 4:10 p.m. in Room 122 of Briggs Hall, UC Davis campus. It also will be on Zoom. The Zoom link:
https://ucdavis.zoom.us/j/95882849672.
His seminar will then be archived on the ENT seminar page.
"Growing scientific evidence indicates that soil fauna and the ecosystem functions and services they provide are threatened by global environmental changes such as those related to climate and land use," Franco says in his abstract. "These threats affect species diversity and functional groups in belowground food webs, impacting ecosystem services that all life depends on. A better understanding of global change impacts on interactions among soil fauna communities and plants, as well as on physical and geochemical processes driven by soil fauna will enhance our ability to predict changes at the ecosystem level."
He will discuss "recent evidence indicating that soil fauna responses may challenge aboveground-based predictions of ecosystem functioning under global change."
Franco joined the Paul O'Neill School of Public and Environmental Affairs, Indiana University in 2012 after serving as a research scientist at the Department of Biology, Colorado State University, from 2018 to 2022, where he was an International Presidential Fellow. Other honors include Senior Global Futures Fellow, Julie Ann Wrigley Global Futures Laboratory.
Franco focuses his research on how modern global environmental changes are affecting soils from tropical crop fields and rainforests to temperate grasslands, according to a faculty post. "His work has contributed to unraveling fundamental roles of microscopic soil animals, such as nematodes, and larger ones such as earthworms and termites, in influencing ecosystem responses to changing climate and land-use regimes."
His areas of interest include soil ecology, soil-plant interactions, ecosystem functioning, global environmental changes, sustainability and sustainable development.
Franco holds a bachelor's degree in agronomy (2008) from Universidade Estadual de Santa Cruz, Brazil; a master's degree (2012) in bioenergy, Universidade Estadual de Londrina, Brazil; and a doctorate (2015) in soil science from the University of São Paulo, Brazil. His dissertation: "Soil Engineering by Macroinvertebrates: Controls on Soil Organic Matter Storage Across Land Use."
Nematologist Amanda Hodson, assistant professor of soil ecology and pest management, is coordinating the ENT seminars. The full list is here. For more information or for technical issues, contact Hodson at akhodson@ucdavis.edu.
handfull of dirt
Franco: Deciphering Soil Macrobiome and Ecosystem Responses to Global Change
It promises to be an outstanding seminar. André Custodio Franco, assistant professor, Indiana University, Bloomington, will speak on "Deciphering the Soil Macrobiome: Belowground Communities Driving Ecosystem Responses to Global Change" at a...
What's up with soil and global change? Andre Franco of Indiana University will speak on "Deciphering the Soil Macrobiome: Belowground Communities Driving Ecosystem Responses to Global Change" at 4:10 p.m., Monday, Nov. 18 in 122 Briggs Hall. It also will be on Zoom and then archived. (Photo by Kathy Keatley Garvey)
Extreme weather accelerates nitrate pollution in groundwater
Extreme weather spurred by climate change, including droughts and heavy rains, may increase the risk of nitrates from fertilizers ending up in groundwater, according to a recent study from researchers at the University of California, Davis. The study found heavy rains after a drought caused nitrates to seep 33 feet under farm fields in as little as 10 days. The study was published in Water Resources Research.
“The conventional wisdom was that it could take several weeks to years for nitrates to move from the crop root zones to reach groundwater,” said corresponding author Isaya Kisekka, a professor in the Departments of Land, Air and Water Resources and Biological and Agricultural Engineering. “We found these extreme events, such as California's atmospheric rivers, are going to move nitrate more quickly.”
In this study, different methods were used to measure how much nitrate, a component of nitrogen fertilizer, was seeping down through the soil in a tomato and cucumber crop near Esparto, California. Scientists conducted their research from 2021 until 2023 when California was experiencing periods of drought followed by atmospheric rivers. They measured nitrate during both the growing seasons and the rainy seasons.
Drought can leave more nitrogen in soil
Previous studies have shown about 40% of nitrogen fertilizer used for vegetables isn't absorbed by the plants but remains in the soil. During droughts, crops don't use nitrogen efficiently, leading to excess nitrogen in the soil. This study found that if a drought is then followed by heavy rainfall, that sudden burst of water causes nitrate to seep in groundwater more quickly. The nitrate concentration in the shallow groundwater exceeded the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter for drinking water.
“In California, we often say we swing between droughts and floods,” said Kisekka. “These extreme events that come with climate change are going to make the risk of these chemicals ending up in our drinking water much more severe.”
Groundwater is the primary source of drinking water for most of California's Central Valley. In some regions, such as the Tulare Lake Basin, nearly one-third of drinking and irrigation wells exceed the EPA's safe nitrate level. High nitrate levels in drinking water can increase health risks, especially for young children. It may also increase the risk of colorectal cancer.
Need for real-time soil nitrate monitoring
Central Valley farmers are required to report to the Regional Water Board how much nitrogen they applied to their field and how much was removed as part of the crop's yield. The study compared different ways of monitoring when nitrate from fertilizers seep into groundwater. Kisekka said the results highlight the need for affordable, real-time soil nitrate monitoring tools to help farmers manage fertilizer use efficiently.
By using conservation practices that limit leftover nitrates in the crop's root zone after harvest, farmers can help reduce nitrate contamination in groundwater.
This study's data will also help improve a model called SWAT, which is used to track nitrate seepage into groundwater across California's Central Valley. This effort is part of the Central Valley Water Board's program to regulate irrigated farmlands.
Other UC Davis authors include Iael Raij Hoffman, Thomas Harter and Helen Dahlke.
The study was supported by the USDA Natural Resource Conservation Service through its Conservation Effects Assessment Project. The national project is designed to assess the effectiveness of conservation practices across different watersheds. The study also had support from the USDA National Institute of Food and Agriculture.
Wild Fire and Soil
Low-severity wildland fires and prescribed burns have long been presumed by scientists and resource managers to be harmless to soils, but this may not be the case, new research shows.
According to two new studies by a team from the University of California, Merced (UCM) and the Desert Research Institute (DRI), low-severity burns - in which fire moves quickly and soil temperature does not exceed 250oC (482oF) - cause damage to soil structure and organic matter in ways that are not immediately apparent after a fire.
"When you have a high-severity fire, you burn off the organic matter from the soil and the impact is immediate," said Teamrat Ghezzehei, Ph.D., principal investigator of the two studies and Associate Professor of Environmental Soil Physics at UCM. "In a low-severity fire, the organic matter doesn't burn off, and there is no visible destruction right away. But the burning weakens the soil structure, and unless you come back at a later time and carefully look at the soil, you wouldn't notice the damage."
DRI researcher Markus Berli, Ph.D., Associate Research Professor of Environmental Science, became interested in studying this phenomenon while visiting a burned area near Ely, Nev. in 2009, where he made the unexpected observation that a prescribed, low-severity fire had resulted in soil structure damage in the burned area. He and several colleagues from DRI conducted a follow-up study on another controlled burn in the area, and found that soil structure that appeared to be fine immediately after a fire but deteriorated over the weeks and months that followed. Berli then teamed up with Ghezzehei and a team from UCM that included graduate student Mathew Jian, and Associate Professor Asmeret Asefaw Berhe, Ph.D., to further investigate.
Soil consists of large and small mineral particles (gravel, sand, silt, and clay) which are bound together by organic matter, water and other materials to form aggregates. When soil aggregates are exposed to severe fires, the organic matter burns, altering the physical structure of the soil and increasing the risk of erosion in burned areas. In low-severity burn areas where organic matter doesn't experience significant losses, the team wondered if the soil structure was being degraded by another process, such as by the boiling of water held within soil aggregates?
In a study published in AGU Geophysical Research Letters in May 2018, the UCM-DRI team investigated this question, using soil samples from an unburned forest area in Mariposa County, Calif. and from unburned shrubland in Clark County, Nev. to analyze the impacts of low-severity fires on soil structure. They heated soil aggregates to temperatures that simulated the conditions of a low-severity fire (175oC/347oF) over a 15-minute period, then looked for changes in the soil's internal pore pressure and tensile strength (the force required to pull the aggregate apart).
During the experiment, they observed that pore pressure within the soil aggregates rose to a peak as water boiled and vaporized, then dropped as the bonds in the soil aggregates broke and vapor escaped. Tensile strength measurements showed that the wetter soil aggregates had been weakened more than drier soil samples during this process.
"Our results show that the heat produced by low-severity fires is actually enough to do damage to soil structure, and that the damage is worse if the soils are wet," Berli explained. "This is important information for resource managers because it implies that prescribed burns and other fires that occur during wetter times of year may be more harmful to soils than fires that occur during dry times."Next, the research team wondered what the impact of this structural degradation was on the organic matter that the soil structure normally protects. Soil organic matter consists primarily of microbes and decomposing plant tissue, and contributes to the overall stability and water-holding capacity of soils.
In a second study that was published in Frontiers in Environmental Science in late July, the UCM-DRI research team conducted simulated burn experiments to weaken the structure of the soil aggregates, and tested the soils for changes in quality and quantity of several types of organic matter over a 70-day period.
They found that heating of soils led to the release of organic carbon into the atmosphere as CO2 during the weeks and months after the fire, and again found that the highest levels of degradation occurred in soils that were moist. This loss of organic carbon is important for several reasons, Ghezzehei explained.
"The loss of organic matter from soil to the atmosphere directly contributes to climate change, because that carbon is released as CO2," Ghezzehei said. "Organic matter that is lost due to fires is also the most important reserve of nutrients for soil micro-organisms, and it is the glue that holds soil aggregates together. Once you lose the structure, there are a lot of other things that happen. For example, infiltration becomes slower, you get more runoff, you have erosion."
Although the research team's findings showed several detrimental effects of fire on soils, low-severity wildfires and prescribed burns are known to benefit ecosystems in other ways -- recycling nutrients back into the soil and getting rid of overgrown vegetation, for example. It is not yet clear whether the negative impacts on soil associated with these low-severity fires outweigh the positives, Berli says, but the team hopes that their research results will help to inform land managers as they manage wildfires and plan prescribed burns.
"There is very little fuel in arid and semi-arid areas, and thus fires tend to be short lived and relatively low in peak temperature," Ghezzehei said. "In contrast to the hot fires and that burn for days and weeks that we see in the news, these seem to be benign and we usually treat them as such. Our work shows that low-severity fires are not as harmless as they may appear."
The study, "Soil Structural Degradation During Low?Severity Burns," was published on May 31, 2018 in the journal AGU Geophysical Research Letters and is available here: https:/
The study, "Vulnerability of Physically Protected Soil Organic Carbon to Loss Under Low Severity Fires," was published July 19, 2018 in the journal Frontiers in Environmental Science, and is available here: https:/
IMG 2031
Hans Jenny and the Art of Soil or Soil in Art
Hans Jenny (1899-1992) was a soils teacher at UC Berkeley, a pedologist. He distilled the factors that drive soil formation into an equation signified as CLORPT. The CLimate, Organisms, Relief, Parent material and Time that create soil. This might all sound academic, but this approach has helped us better understand how soils form from rock or a base material (Parent Material) to become what we see as soil today. And what we will see as soil tomorrow. He was a firm advocate for soil organic matter (SOM) and spent much of his energy showing the value of protecting SOM and how to show its value to not just agriculture, but the landscape and its health. In a 1980 Science magazine letter he said, “The humus capital, which is substantial, deserves being maintained because good soils are a national asset.” It fits right in with our ideas of carbon sequestration today.
He had a real love for soil and an eye for its beauty. He was interviewed back in 1984 for the Journal of Soil and Water Conservation where he shared some of his views.
http://nesoil.com/upload/Hans_Jenny_Interview.pdf
“Over the years I have acquired a kind of reverence for the soil, for the creature-world inside it, and for its character expressed in the profile features.”
“Soil speaks to us through the colors and sculptures of its profile, thereby revealing its personality: we acknowledge it by giving soil a name, albeit in a foreign tongue, but we don't mention our emotional involvements…”
Hans Jenny went “Hollywood” in 1983 by collaborating with David Bellamy of the BBC. The documentary covers the concept of CLORPT referred to in the interview. It's spoken in a pretty thick English accent, so you might want to read up about the Ecological Staircase that exemplifies soil formation. The transect of soils and plants that are discussed are at Jughandle State Park in Mendocino.
David Bellamy's New World explaining Hans Jenny's CLOPRT, Part 1 y
“Soil contains over a thousand different species of lower animals, the earthworms, pill bugs, nematodes, millipedes, termites, ants, springtails, and amoebas, not to mention the millions of molds and bacteria…If all the elephants in Africa were shot, we would barely notice it, but if the nitrogen-fixing bacteria in the soil, or the nitrifiers, were eliminated, most of us would not survive for long because the soil could no longer support us. I can't help thinking of the claim that healthy soils make healthy people, and as an extension, I am intrigued by the thought that good soils make good people, but that notion seems untenable. Well, not wholly so. Working in the garden with spade and hoe soothes the minds of many people….”
“Soil speaks to us through the colors and sculptures of its profile, thereby revealing its personality: we acknowledge it by giving soil a name, albeit in a foreign tongue, but we don't mention our emotional involvements…”
Jenny also studied how we have viewed soil in art over the ages. He gave presentations on the progression over time of how our views have changed from broad nondescript representations to elaborate characterizations and on to more idealized shapes. Check out this essay he did for the Pontifical Academy of Sciences in 1968 after years of roaming art museums - The Image of Soil in Landscape Art.
And more on the art of soil through the ages from a different author
https://www.sciencedirect.com/science/article/abs/pii/S034181620900112X
Arbor Day - Grant Wood
arbor day grant wood
