Encountering Microbiomes in the Garden

Your garden soil contains millions to billions of individual microorganisms, including bacteria, fungi, viruses, and archaea, representing tens of thousands of different microbial species. Humans evolved for millenia in the presence of these environmental microbes associated with vegetation, soil, water, and wildlife. Our immune systems are not only adapted to coexist with the majority of these microbes, but may even require that interaction to function properly. Emerging scientific evidence suggests that exposure to soil microbes trains the immune system, reduces inflammation, and improves mental health (Rook, 2013). For example, the common soil bacterium Mycobacterium vaccae has been found to have positive impacts on stress tolerance and mental health (Matthews and Jenks, 2013), while other research has shown that children exposed to greater microbial diversity, such as that encountered in farming environments, tend to have lower prevalence of autoimmune disorders, including allergies and asthma, than their urban counterparts (Hanski et al., 2012).

The primary goal of the Garden(er) Microbiome Project was to understand how much microbial transfer from soil to skin occurs during gardening activities, what types of microorganisms are transferred, and how long they can persist on the skin. We are also interested in exploring how soil microbial communities vary with different management practices (e.g., organic vs. conventional) and geographic locations, as we know that microbes play critical roles in soil nutrient cycling, carbon sequestration, pollutant degradation, and, of course, crop health.

To accomplish this study, we recruited 40 gardeners to collect microbial samples from their garden soil and from the surface of their skin (hands). All samples were collected in July–September, 2020, and were equally distributed between the Willamette Valley and High Desert regions, as well as between self-reported organic and non-organic management practices. Each volunteer was asked to collect soil samples from three different garden beds and skin microbiome swabs before, after, ~12 hours after, and 24 hours after gardening (Figure 1). To identify bacterial taxa (different types of bacteria) present in the samples, we used Earth Microbiome Project protocols to sequence the V4 region of the bacterial 16S rRNA gene.

Volunteers collected samples from their garden soil and hand surface microbiome.
Figure 1. Volunteers collected samples from their garden soil and hand surface microbiome.

Preliminary results

In garden soil samples, we observed over 8.5 million individual bacteria, representing about 45,000 different bacterial species. In skin microbiome samples, we observed over 6 million individual bacteria, representing almost 13,000 different bacterial species. Of all these bacterial species, there were just over 7,500 that were shared between garden soils and gardeners’ skin microbiomes over the course of the study (Figure 2).

There were 39,705 bacterial species found only in garden soils, 5,197 species found only in skin microbiome samples, and 7,652 that were found in both.
Figure 2. Unique and shared bacterial taxa found in garden soil and skin surface samples.

Our initial hypothesis was that skin microbiome samples would be more similar to soil samples immediately after gardening, due to microbial transfer from soil to skin during direct contact. We also expected that the skin microbiome would return to baseline (before gardening) after a period of time, depending on individual behaviors, such as washing hands and bathing. It turned out that soil microbial communities were very different than those found on skin. Interestingly, skin microbiome samples tended to be dominated by a small number of taxa, though they were not always the same taxa at different sampling times. For many of the study participants, we did indeed see an increase in shared taxa for the skin samples collected immediately after gardening (Figure 3). However, soil microbes were generally transient on the skin and were no longer present after 12 hours. We note that the COVID-19 pandemic may have influenced hand-washing behaviors and use of hand sanitizers, which could have had additional unexpected impacts on the skin microbiome.

Number of bacterial taxa shared between garden soil and skin microbiome samples increases after gardening, particularly for individuals who spend more than 1 hour gardening, but returns to baseline within 12 hours.
Figure 3. Bacterial transfer and persistence on skin after gardening.

Though it was beyond the scope of the project to describe life history details about every type of bacteria that was found, we did investigate a handful of taxa that were highly abundant in many samples. In garden soil, many of the most abundant bacteria belonged to the genus Pseudomonas. In a recent paper, Sah and Singh (2016) state, “The genus Pseudomonas encompasses arguably one of the most complex, diverse, and ecologically significant group of bacteria on the planet. Members of the genus are found in large numbers in all the major natural environments (terrestrial, freshwater, and marine) and also form intimate associations with plants and animals.” Importantly for gardens, several species of Pseudomonas are able to promote plant growth, while others are well-known plant pathogens. Members of the genus Sphingomonas were also common soil inhabitants found in this study. Sphingomonads are broadly distributed in the environment, including soil, water, air, and plant leaves. Only one species of Sphingomonas is known to cause disease in humans, typically in hospital-acquired infections (Balkwill et al., 2006). A third genus of interest from garden soils was Streptomyces. This is a large genus with over 500 members that are ubiquitous in soils. They are known to form symbiotic relationships with plants and animals, and they are responsible for the production of over 2/3 of all known antibiotics (Antoraz et al., 2015). Streptomyces also produce the chemical compound geosmin, which gives soil its earthy smell (Seipke et al., 2012).

The composition of skin microbiome samples in this study varied wildly from individual to individual, and sometimes even for the same individual at different time points. Among the most abundant taxa we found were members of the genera Pantoea, Acinetobacter, Bacillus, and Klebsiella, as well as Pseudomonas, which was described above. Generally speaking, these are very diverse genera and are widespread in many environments, including soil and human skin. Some Pantoea species produce antimicrobial compounds that can help control fire blight in fruit trees (Walterson and Stavrinides, 2015). The genus Acinetobacter contains two species of interest for health reasons—A. baumannii is typically found in wet environments and is a notable opportunistic pathogen associated with hospital-acquired infections (Howard et al., 2012), whereas exposure to environmental sources of A. lwoffii is thought to protect against development of allergies, although it can also cause infection in immunocompromised individuals (Debarry et al., 2007). Members of the genus Bacillus have been explored for potential probiotics (Elshaghabee et al., 2017), and the genus Klebsiella is somewhat notorious for its human pathogenic members. However, Klebsiella, Pantoea, and several other members of the Enterobacteriaceae family have highly similar DNA sequences in the region that we targeted, so these composition results should be interpreted cautiously.

Conclusion

This study represents one of the very first investigations of garden soil microbiomes and, to our knowledge, the only one that explores the ability of soil microbes to transfer and persist on human skin after typical gardening activities. Overall, we found that garden soils tend to have far greater bacterial diversity than skin microbiome samples. Bacterial community composition was largely similar across different garden beds, whereas skin microbiome composition varied dramatically. Some soil microbes appeared to transfer onto skin during direct contact with soil, but they were generally gone within 12 hours, suggesting a low ability to permanently colonize skin. However, a daily gardening routine with repeated and extended contact with soil likely reinoculates the skin such that soil microbes are like a regular visitor during the growing season.

The specific ecological role of most microbes, both in soil and on skin, is a relatively new area of investigation garnering intense interest. However, few, if any, concrete recommendations are currently available to guide actions towards improving plant and human health. A primary goal of this study is to gather baseline data for future studies, which are needed to further explore the impact of daily soil contact over longer time periods (e.g. entire growing season), how changes in gardeners’ skin microbiomes compare with non-gardeners, and whether consumption of fresh garden produce affects the gut microbiome.

Happy 50th Anniversary of Earth Day

Today is the 50th anniversary of earth day. I am almost as old as earth day (I will turn 50, next February), and am finding myself in a reflective mood.

Ever since I was a child, I have been fascinated by and loved nature. I used to try and catch lightning bugs, and put them in a mason jar, hoping to catch so many that I could make a lantern. Today, when I visit my folks near my childhood home, nary a lightning bug can be found. Scientists suspect that increased landscape development has removed the open field habitats and forests that the lightning bugs depend upon to display their mating signals and to live. Light pollution likely also plays a role.

lightning bug 8758
Eastern Lightning Bug. Photo Credit: Terry Priest. https://www.flickr.com/photos/artfarmer/197649535

My time in college was my first real exposure to nature. I worked at Patuxent Wildlife Research Center, supporting the work of James Wagner when he was a graduate student at UMBC. He was studying wolf spiders, and I fell in love with these amazing creatures. Did you know that wolf spider mommas carry their young on their back ~ at least for the first few days of a baby spider’s life? Did you know that to collect wolf spiders, you go out at night with a flashlight . . . shining the flashlight into the forest floor litter, to find eight tiny glowing eyes staring back at you? Wolf spider eyes glow, as an adaptation to capture more light (enabling them to see better) when hunting at night. Like a cat’s eye, wolf spiders have a tapetum at the back of their eye . . . a mirror that re-reflects light back out, and lets the spider’s eyes have a second shot at capturing that light. My time working with James was magical. For the first time in my life, I gained the skills to identify trees, and wildflowers, and birds, and insects. I tell people that it was as if a scrim had been lifted from my eyes, and I saw the world in an entirely different light. I was forever changed, by this newfound knowledge that allowed me to ‘read’ the natural world in a different way.

Behind the rusty eyes
A wolf spider. Photo Credit: Jean and Fred. https://www.flickr.com/photos/jean_hort/4430861610

As a graduate student, I studied salt marsh insects on the New Jersey coastline. I had never been to a salt marsh before, despite living within an hour of the ribbon of salt marsh that hugs the eastern seaboard. I saw horseshoe crabs for the very first time. I saw the fishing spiders in the genus Dolomedes that I had read about in books. I went bird watching and butterfly hunting with scientists who were generous with their time and knowledge, most notably, my advisor, Robert Denno. Now, so much of that ribbon of coastline has been destroyed. What remains is at risk due to increased nutrient pollution from fertlizers and run-off.

Big cordgrass salt marsh
Tall grass in an eastern salt marsh. Photo Credit: Ecological Society of America. https://www.flickr.com/photos/ecologicalsocietyofamerica/25086412492

My post-doctoral work was spent in California on many projects, including studying the food webs of cotton fields that were using organic or conventional production practices. From talking to the farmers and stakeholders, I learned that there are not insurmountable impediments to growing organic cotton. The problem was that there was a limited market for organic cotton, grown in the United States. Growers who would plant organic cotton faced an uncertain market and reduced yields. Often, reduced yields might be compensated for with a premium price for organic products. But not in the case of US-grown organic cotton. This is when I first started to realize that science can not work in a silo, but that an understanding of economics and the social sciences is critical to promoting more sustainable solutions.

My first faculty position was at Fordham University in the Bronx. I had no idea what I would study, as an entomologist in the Bronx. Luckily, I had the great fortune of taking on Kevin Matteson as my first graduate student. Kevin had been studying the birds of New York City community gardens. I asked him if he might be willing to instead study insects. His work was ground-breaking and is heavily cited, showing the potential of small garden fragments in one of the most heavily populated cities in the world, to support a diverse and abundant assemblage of insects. He also showed that the strongest predictor of butterfly and bee diversity in gardens was floral cover. Through Kevin’s work, as well as associated work by Evelyn Fetridge, Peter Werrell, and others in our Fordham lab group, I became convinced that the decisions that we make in home and community gardens have the potential to make a real and positive difference in this world.

I came to OSU in 2007, for the opportunity to work with about 30 faculty and staff and between 3,000-4,000 volunteers who were dedicated to sustainable gardening. Coming from a teaching and research position to an Extension position was initially a challenge for me. I recognized importance of bringing good science to Extension and outreach work, but I didn’t know exactly how I would or could contribute. In 2016, I started the Garden Ecology Lab at OSU, mostly because I was more convinced than ever, that having good science to guide garden design and management decisions can truly make a positive difference in this world. I sometimes talk about ‘how gardening will save the world’, which is a lofty and aspirational goal. But, I truly believe (and science backs up this belief), that the decisions that we make on the small parcels of land that we might have access to in a community or home garden matter. These design and management decisions can either improve our environment (by provisioning habitat for pollinators and other wildlife) or harm our environment (by contributing to nutrient runoff in our waterways, or by wasting water when irrigation systems fall on the sidewalk more than on our plants).

This is one reason that I stand in awe of the Master Gardener Program. When I was purely a researcher, rarely interacting with the public, I doubt that many people were able to take our research findings and apply them in their own yard. When I was initially struggling with my new Extension position, I went to my former Department Head at the University of Maryland entomology deparment, Mike Raupp. Mike had a lot of experience with Extension and outreach, in addition to being a world-reknown researcher and a super-nice person. I remember him saying ‘Gail, when you publish a research paper, you’re lucky if 20 eggheads will read it. When you talk to the Master Gardeners, you have the opportunity to make real change in this world.’

And together with the Master Gardeners, I hope that is what we have done. I hope that is what we will continue to do. I hope that we find new and novel ways to discover how folks can manage pests without pesticides, to reduce water use in the home garden, and to build pollinator- and bird-friendly habitat. And then I hope that we will reach and teach our neigbhors and friends how to appreciate the biodiversity in their own back yard, and the small changes that they can make to improve the garden environment that they tend. I hope that we can instill a wonder for the natural world in the next generations, and to preserve or improve the natural world, so that our kids, and grandkids, and subsequent generations can hunt for lightning bugs, or spiders, or butterflies.

And I want to do it with you, dear gardeners. Together, we truly can make a difference.

Sharing my Story – Angelee Calder

STEM Leaders Program Professional Head shot

Hello Blog Readers!

I am writing here to share my story! Possibly also to toot my horn a bit. I am extremely proud of what I have been up to lately!

In the Lab…

Me Presenting my Lab Poster at the STEM Leaders Symposium

I joined this lab through the STEM Leaders program. They connected me to the Urban Ecology lab where I started work in January 2019. January 2020, I presented a research poster at the STEM Leaders Symposium on Professor Gail Langellotto’s and Aaron Anderson’s research projects, as well as my role in them. My role is, primarily, to provide support to the Lab’s research projects. My tasks included things like cleaning, data basing, and pinning bees. I also provided help in the field by weeding plants, observing pollinators, and collecting specimens. The research projects I contributed to are amazing and I am proud of the work I have done. I am very thankful for knowledge and skills I have gained along the way. As a result of these skills, I have been able to be successful in school and my other opportunities.

Starting at Oregon State University…

When I transferred to Oregon State University (OSU) from Southwestern Oregon Community College, I knew that I wanted to participate in research. I had no idea where to begin. After earning a spot in the program, STEM Leaders provided me with the tools I needed to be successful in a lab. They then connected me with Gail Langellotto, my first choice in labs. Since starting work, I have gained a new passion for urban ecology and pollinators. I have also learned many skills that will directly translate to, and benefit me, in my journey to a possible master’s degree and my future career.

In my time at OSU, I have been presented with many opportunities. Originally, I was concerned about finding a community here at OSU. I am from the small town of Baker City, Oregon. The biggest town I had lived in, before Corvallis, was Coos Bay, Oregon.  Since my first term, I have been participating in TRIO (student support services), STEM Leader’s, and the Organic Grower’s Club. These programs have provided me with a wide range of support and connections.

Current Events…

From Left to Right: Javier Nieto – Dean of OSU College of Public Health, Allison Myers – Director, OSU Center for Health Innovation, Me – Angelee Calder, Jock Mills – OSU Director of Government Relations

Recently, I have been involved with the OSU Human Resource Service Center’s Advisory Board and the Presidential Student Legislative Advocacy program (PSLA). PSLA is a non-credit course aimed to reach students who want to be advocates for Oregon State University. They work to teach and engage students in policy issues related to our interests. Through this class, I was able to advocate for the program “Coast to Forest”, from OSU’s College of Public Health. This program aims to reduce mental health issues and opioid addiction in four rural counties across Oregon, including Baker County. I was able to advocate for this much-needed program by giving an invited personal testimony to the Oregon Senate Committee on Public Health. This was my first time participating in the public process. For that reason, I was encouraged to pursue an internship at the State Capitol.

Me Sitting at Governor Kate Brown’s Desk with
Senator Arnie Roblan

Later, I earned an internship position at the State Capitol. I am now an intern in State Representative Caddy Mckeown’s office during my final winter term here at OSU. As a first generation, low income, and Agricultural Science student, I never thought that I would have the opportunity to learn about the legislative process first-hand by doing office work in a Representative’s office. I am extremely thankful for this opportunity as I have already learned a lot and have made many new connections. I am looking forward to learning more as we progress through the 2020 legislative short session. Similarly, I am extremely excited for my other upcoming events.

Future Events…

Me Walking and Talking with Representative Caddy Mckeown to a Speaking Event

Next term, my final term at OSU, I will embark on my biggest journey yet! I earned a full time internship at the Monteverde Institute in Costa Rica! This is a huge leap for me! I have never left the country, have hardly left the Pacific Northwest, and have never travelled alone. I could not be any more excited! Here, I will be working with the local farmers to develop farm designs and do soil analysis. I will work to advance the Monteverde Institute’s goal to advancing sustainability on a global level. Additionally, I have the opportunity to design a local pollinator garden at the local elementary school and educate the children on it! In this way, I will be bringing a bit of the Garden Ecology Lab to Costa Rica with me!

Finally, my graduation will be in June 2020, after I return from my 2.5-month internship in Costa Rica. I will have earned a major in Agricultural Science and a minor in Comparative International Agriculture. My time here at Oregon State has been short, yet very fruitful. It is sad to see my educational journey end. I will be eternally grateful to all the people I have met along the way. I would not have made it where I am without their guidance and help. They will not ever know how truly grateful I am and how impactful their presence has been in my life. Thank you, Gail Langellotto for your leadership, knowledge, and the opportunities you have given me!  

I will be blogging from Costa Rica. If you would like to follow this, or learn a bit more about me you can find my personal website at the link below.

https://angeleecalder.weebly.com/

PolliNation Podcast and Lab Update

If you love bees, and you have not yet subscribed to PolliNation, you’re missing out! OSU Professor and PolliNation podcast host, Andony Melathopolous, does a wonderful job assembling a diverse array of guests to talk all things pollinator.

Aaron Anderson recently joined Andony on episode 94 of thePolliNation podcast, to talk about his research on native plants, different insect groups, and gardeners.

Aaron talks about the 100+ study plots that he manages (two of which you can see, below), as well as which plants were most attractive to bees (such as the California poppy, on the left) versus those that were more attractive to gardeners (such as the Oregon iris, on the right).

In other news, our lab group has been very busy. All of the 2017 and 2018 bees from our garden pollinator study have been identified to species (unless they are truly recalcitrant to being ID’d to the level of species).  Gabe has been working with Lincoln Best to identify the 2018 bees.  The 2017 were verified by Sara Kornbluth, and provided a great reference collection against which we could compare the 2018 bees. Gabe has been a short-time member of our lab group, but his expertise has been a huge benefit to our program. He leaves us at the end of April to start field work in the College of Forestry. After that, he heads to UC Davis to do his Ph.D.

For the garden bee project, we have >50 verified species of bees collected from Portland-area gardens, with a few more at the morpho-species level. This summer will be our final year of collections.

This summer will also be Aaron’s final year of field work at the North Willamette Research and Extension Center. This final year will help to resolve some of the differences we saw between his 2017 and 2018 data set.

After two years of amazing assistance in the lab and in the field, Isabella has started an independent research project on campus. She has planted some of Aaron’s study plants in gardens on campus, and is looking to see if bee visitation and bee communities markedly change, when you take them out of single-species plantings (like Aaron is studying) and put them into a garden setting.

Mykl is working to write up his urban soils data for publication. We are also hoping to do a side publication, comparing the soil types that we’re finding in home gardens, and seeing how they align with the types of soils that nesting bees prefer.

Lauren is writing up her capstone paper, and is preparing to defend this term. She surveyed gardeners to try to understand how well they can identify bees from other insects, and how well they knew bee-friendly plants from those that offered few or no nectar/pollen resources to bees.

Signe is taking the data that we are collecting, and working our findings into the online Master Gardener course. The best part of our work is being able to see gardeners put some of our research-based recommendations into action. Signe plays a huge role in translating our work for the general public.

Angelee is a relatively new member of the lab. She comes to us from the OSU STEM Leaders program. She’s learning lab protocols and lending a hand on just about every project. She has been a joy to work with.

Lucas has moved on from the lab, but still helps us with remote data-basing work, on occasion. He was a joy to work with, and I feel lucky that he stuck with us for a few years.

This fall, Jen will be joining our group as a new M.S. student. We will also be close to launching the first course in the online Urban Agriculture certificate program, which is being spear-headed by Mykl. We should also be pushing out a few more papers from our garden work, to join our first concept paper on the value of urban garden bees to urban and peri-urban agriculture.

 

Webinar on Willamette Valley Native Plants and Pollinators

Aaron’s webinar on his Ph.D. research has been posted on YouTube.

He highlights some really interesting results from his 2017 and 2018 field seasons, including recommendations for what to plant, if you are interested in attracting native bees to your garden. I’ve asked him to write a blog post, summarizing the results to readers.

Do Gardeners Like the Same Flowers as Bees?

In 2017 and 2018, Aaron and Lucas took weekly counts of bees on their native plant plots. Aaron has summarized the data for 2017 (below) according to bee morpho-type. The morphotype categories are the same general categories that have been used by other researchers: bumblebee, honey bee, green bee, small bee, and big bee. These major bee categories are fairly easy to distinguish from one another in the field. Although, Aaron and I talked quite a bit about whether or not we should combine big bees and small bees into a new category: other bees. When does a small bee become a big bee? We had a general sense that a large Megachile rotundata would be a big bee, and a small Ceratina sp. would be a small bee. But, what about a smaller Megachile species? Is that big bee or a small bee? There is no clear answer.

Aaron and Lucas kept records of big bees vs small bees, as best as they could, but in the end, we might collapse all of that data into an ‘other bee’ category.Aaron recently surveyed gardeners, to ask their opinion on the aesthetics of his study plants. A quick look at the results suggests that gardeners and bees might be attracted to different flowering plants. While Gilia capitata was the most visited plant in Aaron’s study plots, it was ranked 6th most attractive (out of 27 plants) by gardeners. The story gets worse for Madia elegans (2nd with bees, 20th with gardeners), Aster subspicatus (3rd with bees, 14th with gardeners), and Solidago candensis (4th with bees, 23rd with gardeners).

Could it be that bees and gardeners are truly attracted to different types of flowering plants? Or could it be that if gardeners knew about the benefits of these Willamette Valley natives, that they might see a new kind of beauty in these plants?

 

First Bee List from Native Plant Study

We are so lucky that Lincoln Best has been in Oregon, supporting the work of the Oregon Bee Atlas. Linc was kind enough to take a look at Aaron’s bees, before going back to Canada. Aaron is currently taking a bit of time off, following his wedding this past weekend (Congratulations Aaron and Maura!). In everyone’s absence, I’m chomping at the bit to see what bees were identified from Aaron’s study of Willamette Valley native plants. So ~ for your reading pleasure, here is a preliminary list of bees collected from Aaron’s plant plots.

Aaron and Lucas in the native plant study site. You can see the 1m by 1 m plot in the foreground by Aaron, a second one near Lucas, and a few more in the distance.

A few things to note about this list:

  1. I give no mention of abundance of each bee species. Some specimens were caught many, many times off of a flowering plant species. Others were rare, and only caught once.
  2. This list is not all-inclusive. It’s Labor Day. I’m working. I got excited about the bees, and wanted to share. But, I am not carefully going through every small label.
  3. Some bees were only found on one or two flowering plant species ~ even though Aaron’s plots are all in the same 3 acre field (1X1m plots, with each plot separated from every other plot by 6 m).
  4. Yellow-faced bumblebees were collected off of most plants ~ so I am not listing them, below. I also did not look at the honey-bee plant associations.
  5. Linc dissected male genitalia (yes ~ that is how you need to ID some bees to species), and found FOUR Bombus calignosus (all associated with lavender)~ a vulnerable species on the IUCN Red List.
  6. We also have Bombus fervidus, another species on the IUCN Red List (Vulnerable) on lavender, Salvia, and Gilia.

I’ll leave it to Aaron to make a rigorous accounting of bee-flower associations. But for now . . . on this holiday weekend, I was too excited to not take a peek and share initial findings with all o fyou.

Nepeta (non-native comparitor)

Oregano (non-native comparitor)

Salvia (non-native comparitor)

Lavender (non-native comparitor)

Phacelia (native)

Clarkia (native)

Goldenrod (native)

California Poppy (native)

Doug Aster (native)

Oregon Iris (native)

Gilia capitata (native)

Oregon Sunshine

Madia (native)

Sidalcia (native)

Yarrow (native)

Pearly Everlasting (native)

Upcoming Webinars Feature Garden Ecology Lab Research

If you are interested in hearing more about our research, please consider sitting in on one of the upcoming webinars we are presenting, as part of the Advanced Training Series for Master Gardeners, organized by OSU Extension Faculty Member, Brooke Edmunds. Gail will be speaking on August 30th, about garden bees. Aaron will be speaking on October 22 on his native plant research. There is also a presentation in November by Melodie Putnam (not in our lab group ~ but a great speaker) on plant galls.

Webinars qualify for Master Gardener continuing education units in Oregon. The webinars are free, but you must pre-register. After the presentations, all webinar recordings are posted on Brooke’s YouTube channel.

More details, and link to the registration page, can be found, below.

Thursday 8/30 at 11am PT

The latest research on bees in the garden: an update from the OSU Garden Ecology Lab.

Speaker: Dr. Gail Langellotto (OSU)

 https://learn.extension.org/events/3443

Monday 10/22 at 11am PT

‘First Look’: OSU Research on Native Plants in the PNW Garden

Speaker: Aaron Anderson (OSU graduate student)

https://learn.extension.org/events/3494

Monday 11/19 at 11am PT

The Weird and Wonderful World of Plant Galls

Melodie Putnam (OSU Plant Clinic)

https://learn.extension.org/events/3493

Missed a webinar? 

Catch up with the 2018 series here: https://tinyurl.com/yczwxjvr (opens in YouTube)

Urban Garden Soils Study Update

It has been a busy summer in the Garden Ecology Lab!

  • Mykl Nelson successfully defended his thesis on urban garden soils, and graduated with a M.S. in Horticulture this past June.
  • Gail, Aaron, and Mykl all shared their research results with Master Gardeners, at the recent Growing Gardeners conference.
  • Aaron continues his fieldwork, documenting the attractiveness of several Willamette Valley native plants to pollinators. You can find his full list of plants here.
  • Aaron launched the survey part of his research, to document the attractiveness of these same plants to gardeners. If you would like to participate, you can find our recruitment letter, here.
  • Gail and Isabella continue to sample insects on a monthly basis, from 24 Portland area gardens. Our July sample has been pushed to the week of July 30th, because Gail was invited to serve as a panelist on a USDA grant panel. Sampling takes four long days ~ made all the more difficult by Portland’s heat wave. But, sampling during the heat wave will be interesting. Do garden habitats become even more important to bees, when the heat dries up forage in natural and wild habitats? We shall see.
  • Bees from our 2017 sampling effort have been pinned, labelled, and sent to the American Museum of Natural History for expert identification. Thank you to the Oregon Master Gardener Association for a $500 grant to help pay for the expert bee identification.

Today, I’m packing field supplies and clothes for the July 30-August 2nd garden bee sampling effort. It seemed like a good time to provide an update on our garden soils work. I wrote this article for the Hardy Plant Society of Oregon quarterly magazine. I thought that others who are interested in garden ecology might be interested in seeing an update on this work. We are currently working on a manuscript of Mykl’s research, for submission to the journal Urban Ecosystems. In the meantime, some of the highlights can be found below.

**********************

Despite the popularity of urban agriculture, we know virtually nothing about urban agricultural soils, including residential vegetable gardens. We thus studied urban garden soils to get a sense of the characteristics of residential-scale, urban agricultural soils in western Oregon. Last year, we took soil samples from 27 vegetable gardens in Corvallis and Portland, and tested for differences between garden sites based upon bed-type (e.g. raised beds versus in-ground beds). All gardens were managed by certified Extension Master Gardeners.

If you have taken a Master Gardener soils class, perhaps you have heard the soil management mantra ‘just add organic matter!’. This mantra comes from the idea that adding more organic matter (OM) can improve soil tilth and nutrition. However, this mantra was derived from research in large-scale farming systems, where farmers often struggle to raise their soil OM by even 1%, across tens or hundreds of acres of crop production.

We found that nearly every garden that we sampled had an excess of OM (Table 1). Soil management guidelines suggest that farmers should aim for 3-6% soil OM. Across all of our garden study sites, vegetable garden soils were on average 13% OM, by volume. Raised beds were significantly over-enriched in organic matter (15% OM, on average), compared to in-ground beds (10% OM, on average). To put it another way, Master Gardener-tended vegetable gardens were over-enriched in OM by 2-5 times the recommended level!

This excess in organic matter likely contributed to excessive levels of other soil parameters. For example, most garden study sites were above recommended levels for electrical conductivity (a measure of soil ‘salts’). All gardens were above recommended levels for sulfur (S), phosphorus (P), calcium (Ca), and magnesium (Mg) (Table 1). Only nitrogen (N), potassium (K), and boron (B) were generally within recommended levels (Table 1).

Table 1. Percent of garden study sites that were within, above, and below recommended ranges for various soil parameters. OM: organic matter. EC: electrical conductivity. N: nitrogen. S: sulfur. P: phosphorus. K: potassium. Ca: calcium. Mg: magnesium. B: boron.

Soil Parameter Percent of Garden Study Sites
Within Recommended Range Above Recommended range Below Recommended Range
OM 6% 94% 0%
EC 18% 82% 0%
N 70% 30% 0%
S 0% 100% 0%
P 0% 100% 0%
K 73% 24% 3%
Ca 0% 100% 0%
Mg 0% 100% 0%
B 42% 3% 55%

The excessive organic matter in residential-scale garden soils makes sense, when considered in the context of garden size. In small garden plots, gardeners can easily over-apply products which have been recommended for successful, large-scale, agricultural production. It is easy to imagine that the over-abundance of organic matter in soils results from large amounts of compost added to a relatively small area.

Our results point to the importance of conducting periodic soil tests in garden soils. Instead of ‘just adding organic matter’, gardeners need to understand where they are starting from, before adding amendments and fertilizers to their soil. Apply focused applications of specific nutrients (such as boron or nitrogen) to correct nutrient deficiencies, as needed, while avoiding additions of nutrients that are at relatively high levels. For example, nitrogen is extremely mobile in soils, while phosphorus tends to build up over time. Adding focused applications of synthetic (15-0-0) or organic nitrogen (in the form of feather meal) can help meet crop needs without providing excessive amounts of phosphorus, over time. Gardeners who annually apply organic matter to their soils, without the benefit of a soil test, may be unintentionally adding too much phosphorus to their soils. Soils with excessive micronutrients may hinder plant growth. Soils with excessive phosphorus might contribute to water quality issues in their watershed. Excessive phosphorus also harms or kill beneficial mycorrhizal fungi.

Master Gardener Input Needed!

We are soliciting Master Gardener feedback on the attractiveness of the native wildflowers that Aaron Anderson is studying for pollinator plantings. More detail on the study can be found at:

http://blogs.oregonstate.edu/gardenecologylab/native-plants-2/

As we mention, not only are we interested in finding plants that support ecosystem services; we also want to find plants that gardeners find attractive, and that they would want.

This is where you come in. If you are willing, please let us know which ones you would like to see in your own garden, based on their looks, alone. Below is the recruitment letter, with further information about participation. Thank you for your consideration!

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Study: Screening Willamette Valley Wildflowers for attractiveness to Pollinators and Natural Enemies

Graduate Research Assistant: Aaron Anderson (andeaaro@oregonstate.edu; 503-860-9286)

Principal Investigator: Dr. Gail Langellotto (Gail.Langellotto@oregonstate.edu; 541-737-5175)

Dear Master Gardener,

You are invited to take part in a survey that will generate useful information on the ornamental value of pollinator-friendly native wildflowers.

Previous research has shown that urban greenspaces, notably gardens, can provide excellent habitat for pollinators and other invertebrates. The inclusion of pollinator-friendly plantings in gardens has the potential to improve habitat quality and connectivity in otherwise inhospitable landscapes. However, research on which Willamette Valley wildflowers are best to use for these plantings is lacking. Thus, I am conducting a research project to assess the relative attractiveness of 23 wildflower species native to the Willamette Valley (Oregon) to pollinators and natural enemies. Additionally, I would like to assess the aesthetic value of these plants to identify native flowers that are also attractive for ornamental use in home gardens.

As a Master Gardener, I am asking your help with my study, “Screening Willamette Valley Wildflowers for attractiveness to Pollinators and Natural Enemies”.  If you are aged 18 or older, and are currently a Master Gardener, or have been a Master Gardener in the past, I would appreciate it if you could take 10-15 minutes to respond to this survey:

http://bit.ly/OSUNative

Your survey responses will be recorded as a group. Thus, your response will be anonymous.  If the results of this survey are published, your identity will not be made public. The security and confidentiality of information collected from cannot be guaranteed.  Confidentiality will be kept to the extent permitted by the technology being used.  Information collected online can be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses.

Your participation in this study is voluntary and you may refuse to answer any questions(s) for any reason.  There are a limited number of Master Gardeners in Oregon, so your participation in this study is important. If you do not want to participate and do not wish to be contacted further, do not fill out the online questionnaire. There are no foreseeable risks to you as a participant in this project; nor are there any direct benefits. However, your participation is extremely valued.

If you have any questions about the survey, please contact me at 503-860-9286 or via email at andeaaro@oregonstate.edu.  If you have questions about your rights as a participant in this research project, please contact the Oregon State University Institutional Review Board (IRB) Human Protections Administrator at (541) 737-4933 or by email at IRB@oregonstate.edu.

Thank you for your help. I appreciate your consideration.

Sincerely,

Aaron Anderson