People include Noortje (Agronomy), Edwin (Agronomy), Kent (Biology), lhz; CC (Biology), Priscilla (Biology), lhz, Priscila (Biology). Above that, Dr. A. Hope; above that, several of the resident Konza Prairie bison (with smoke in the background from prescribed fire in a nearby watershed).  **picture credit footnote

Animal-microbiome interactions at soil to landscape scales

Yes, microbes are everywhere, have a huge diversity of ways of getting energy from their environments, and through these metabolic activities control the levels and forms of organic and inorganic chemicals in every habitat, including animal host environments. This means animal - including human - health and nutrition is affected by microbes, in analog to microbes' importance for plant, soil and ecosystem health and fertility. Society benefits from the microbial and ecosystem services that we study.

At the landscape scale, animals may have an active effect on soil microbial structure and function. For example, grazing mammals can move nutrients and microorganisms long distances across the landscape, and concurrently make nitrogen more available for plant growth through their digestion products. Our graduate level Microbial Diversity class has been investigating soil microbial distribution, diversity, and soil fertility responses to bison grazing for several years (see left & short YouTube video), and the lab was recently supported by the National Science Foundation to study this in more detail (CAREER.pdf).

What is a grassland without grazers? Pre-European colonization, bison and other large mammals ranged the North American Great Plains. Today, cattle are common, and are managed in a variety of different ways. Through a collaborative project, we will learn how rotational fire management (patch-burn-grazing) affects a diversity of prairie organisms and services, including soil microbes (USDA.pdf).

One goal of this research is to broaden our geographic perspective of grazing effects on soil, by sampling rangelands across the Flint Hills. See this flyer for more detail on the search parameters for private lands participants, and see this example report on bison grazing data for site managers. Contact Lydia Zeglin with any questions.

So, who's really in charge, the microbes, or the animals? Humans are animals too. Because of this, all of our work on *management* effects on soil and water quality and microbes is about understanding animal-microbe interactions. Through a better understanding of these interactions, we gain the ability to nurture positive relationships, and to live and work better, together.

 

Stream ecosystem function
and microbial diversity

Stream ecosystems are perhaps the most dynamic, heterogeneous and biogeochemically active components of the landscape, and carry integrated signals of the watershed management upstream. A large portion of the balance between stream nutrient uptake and export, thus water quality, is mediated by microbiota, but little is understood about the links between microbial diversity and stream function. More work is needed to measure and identify the active components of microbial diversity in streams, the mechanistic links between diversity and function, and to address how population-, community-level or physiological responses of stream microbiota to global change drivers affect stream function.

Does microbial structure and function correlate more with rainfall, or land-use? Do inputs of well defined microbial source communities (say for instance, a batch of cells that has lived in fertilizer waste for decades) affect lotic ecosystem function? Many streams across the USA are intermittent or ephemeral, and these real waters are critical locations of nutrient processing and removal in their watersheds. We're using observational data, manipulative experiments, and biogeochemical, target gene and metagenomics approaches to parse out the effects of microbiome vs. water chemistry on N-cycling function. Two active large collaborative NSF-EPSCoR grants support this work (MAPS.pdf), one is brand new (AIMS.pdf); more results to come.

That's Dr. Burgin's lab at KU in the lower picture, and our super-techs, Janaye (KSU) and Emma (KU). Janaye is hunting biofilms in a Kings Creek pool in the top picture.

BGPE (top): guess which treatment hasn't been burned for >30y?
Other pics show CC and a root ingrowth core, Priscilla and the LiCor for belowground CO2 flux, Matt working to isolate bacteria from the soil.

Grassland ecosystem
sensitivity and recovery
from chronic fertilization

As part of the Konza Prairie Long-Term Ecological Research program, after 30 years, we stopped fertilizing the soil at the Belowground Plots Experiment (BGPE), and are measuring the subsequent changes in soils, microbes, and plants. This will allow us to understand the mechanisms that regulate the time it takes the ecosystem to recover from chronic nitrogen fertilization. The BGPE also includes a long-term factorial fire treatment, so we can learn how fire management affects fertilization sensitivity and recovery.

So far, we have learned that plant production is more sensitive to fertilization in annually burned conditions, soil bacterial and archaeal community composition is more sensitive to fertilization in unburned conditions, and soil fungal and plant community composition is sensitive to both long-term fertilization and the lack of fire. These differential responses are related to the role of fire cessation in causing higher ambient soil nitrogen (N) availability and allowing woody encroachment.

We are in the process of learning how sensitive the key soil microbial activities of nitrification and denitrification were to chronic fertilization, and estimating how these rates of nitrogen loss from the ecosystem might compare to losses driven by fire. These results have major implications for understanding if the added N will stay in the soil, or will leach from the soil into groundwaters as nitrate, or will be returned to the atmosphere as either greenhouse gases, or inert, harmless gases.

From 1986-2016, a total of 300 g of N per square meter of land was added to the prairie (close to 3000 lbs. per acre, at a rate of just under 100 lbs. per acre per year). Where did and where will all of this nitrogen go? Results from this work are showing the extent to which, and how, soil microbial responses to changes in land management affect important ecosystem properties (soil N availability, soil C accumulation, greenhouse gas emission, N loss potential). Check out the Data Nugget (lesson for high school students) that Jaide put together on our work here!

woody encroachment effects on soil carbon cycling

Woody plants are replacing grasses across the Great Plains, and in many other grassy ecosystems globally. The deeper-rooted shrubs deliver new carbon into the soil profile. (1) Will this input stimulate decomposition or carbon storage? (2) Will the whole ecosystem carbon balance change?

Our collaborative project (DOE.pdf) will answer these questions using new empirical data of soil C stocks and cycling activity profiles in native tallgrass prairie and woody-invaded prairie (picture to right), experiments to assess priming potential in these soils, including at depth, and most exciting, use of these data in updated earth systems models that include plant cover change and drought impacts in their predictive capacity.

Drought is increasing across the globe, and woody plants also pull more water from depth. This could have important feedbacks on both vegetation change and carbon storage, particularly in high-clay soils of this region (note color change at depth in the pictured core).

In the late 1970's, these watersheds (above) looked the same. Since then, one was burned annually (left) and one was burned twice (right). The consequent woody encroachment could change soil carbon dynamics (1-m core below, top to right of rotated picture), and the whole ecosystem carbon balance.

---

Kasatochi Island before and after; a patch of Leymus mollis that has vegetatively recovered (supporting a much higher abundance, diversity and activity of soil microbes in the ash below, and more organic matter); lhz and CC working at the reference site on Adak Island. Thanks to the Alaska Maritime National Wildlife Refuge for being so supportive of young scientists who carry as much soil away with them as possible! The Aleutians are stark and beautiful.

Recovery of soil microbial structure and function post-volcanic eruption

Kasatochi Volcano erupted in 2008, burying previously lush Kasatochi Island, Alaska in pyroclastic material. Since, communities of plants, animals and microbes have re-established on certain areas of this new surface, and a multi-disciplinary team of USGS, USFWS and academic scientists is studying this recovery. Volcanism shaped the Aleutian Islands, and results to date suggest the regional biota is resilient to this high- magnitude disturbance.

Microbial colonization of the new surface is directly linked to organic matter inputs - seabird deposition, plant regrowth, aeolian redistribution of pre-eruptive soil. "Recovery" of the soil microbial structure and function has been rapid (~5y), but slower accumulation of organic matter may limit whole ecosystem recovery.

​It is still not clear whether these recovery responses represent regional microbial dynamics, or are uniquely localized patterns. The Aleutian Islands have a mild climate, highly productive vegetation (it's a temperate rain-grassland!)... this creates potential for rapid soil organic matter accumulation though plant growth and high regional microbial dispersal potential due to big weather and seabird populations.

---

---

Microbial turnover & stress responses to intensified drought in Grassland soils

Global change models predict that Great Plains soils will experience longer periods of drying and larger re-wetting events in the future. While altered precipitation does impact microbial function, many prairie soil microbiota are tolerant to the stress of drought. Understanding the mechanisms driving stress tolerance, and the prevalence of these traits in native and agricultural soils, will help in predicting and preparing for the future.

We ran lab experiments that showed greater taxon-specific sensitivity (death) through dry-down/re-wet cycles in soils with a history of less drought, which was also associated with more soil C loss. Also, we evlauated how a simulated "megadrought" affects microbiota in situ in soils with different drought histories.

This work was done in collaboration with investigators on the Rainfall Manipulation Plots (RaMPs, at right).

Konza prairie at top. This is Nature Conservancy land managed by the K-State Konza Prairie Biological Station. Thanks to Dr. Hartnett for letting us use his Jeep Liberty (Sean and Victoria sieving)!

---

* thanks to Roger Topp for the amazing pictures of the Aleutians. I took some, but the ones that look really good are his :)
** thanks to Barb Van Slyke for the man-make-fire picture. She also has some superior photography skills.

​Updated May 2021