Earth and Environment ︱ Dr Mary Ann Bruns MANAGEMENT “TARGET” NATIVE MICROBIAL HABITAT UNDERSTUDIED PRACTICE SOIL PROPERTY CONDITIONS METABOLIC REACTIONS Greater retention of CO Biophysical 2 Heterotrophic CO2 and volatile compounds integrity assimilation within the soil More varied biochemical High proportion of Making the most Reduced/ gradients and micro-site macroaggregate No tillage heterogeneity volume (Eh, pH, pO2, pCO2, volatile organics) Macropore Cover crop connectivity Facilitated diffusion of microbes for soil H2 Oxidation and tortuosity of gases and volatile compounds Increased proportion Crop High root density of rhizosphere-affected DNRA rotations and turnover restoration and function soil and particulate carbon substrates umans have drastically transformed types of soil systems can enhance Organic Mary Ann Bruns is Associate Increased supply Earth’s protective soil layers, with soil functionality by improving living amendments Long periods Professor of Soil Microbiology of root exudation of labile carbon in the Department of Ecosystem Hagriculture and mining being conditions for microbes. They define substrates among the most damaging land uses. functionality as the soil’s biologically Science and Management at Diversified root More varied supply of Atypical nosZ- Penn State University. The Severe disturbances to soils result in driven ability to capture, retain, exudates labile carbon substrates denitrification Bruns research group aims their failure to hold water and recycle and recycle water and nutrients. nutrients, two critical soil functions to to understand how beneficial High concentration functions of soil microorganisms mitigate biogeochemical and hydrological The team’s restoration research recognises and diverse carbon - Fungal NO3 can be promoted through better imbalances on a global scale. Bruns that soil functionality depends on sources Uptake management of agricultural explains: “Well-established interactions sustaining microbial viability and activity. Figure 2. Microbe-informed soil management can promote beneficial microbial processes (from Bhowmiket al., 2017.) Respective colours of text, and mining-impacted lands. among plant roots, fungi, bacteria A schematic from their recent paper (Fig. connecting arrows, and lines are blue (for physical structure improvement); green (for increased plant inputs); and red (for more diverse organic inputs). The group focuses on microbial and micro- and macrofauna are all 2) depicts how microbe-informed soil processes important in nutrient destroyed once vegetation is removed management can promote beneficial and other microbes. During degradation microbial conversion of highly mobile soils are mostly comprised of rocky cycling and water retention. and soil is upturned, buried, or eroded microbial processes through reduced of organic compounds, microbes also nitrates to ammonium. subsoils that have been stockpiled Their goal is to identify away. We want to know how functional disturbance and continued provision produce secretions that combine with less and redistributed. Microbes in these practices (Fig 1) which sustain microbial-root networks can be brought of organic residues. Here, we take a closer degradable residues to create stabilized Bruns hypothesises that moister, more soils have extremely poor living microbially assisted delivery back most effectively in altered soils look at their research which states the organic matter. Because it acts as a water energy-rich conditions in soils will conditions, with very low organic matter of water and nutrients to plants to improve nutrient recycling, water case for taking microbes into account and nutrient-retaining sponge, stabilized and result in more cost-effective retention, and plant productivity.” when managing agricultural and mining- organic matter improves microbial habitat. and lasting restoration. impacted soils, respectively. Thus, microbial degradative activity exerts The team’s restoration research recognises Agricultural and mining-impacted soils positive feedbacks on soil bio-function. that soil functionality depends on differ not only in nutrient and water RESTORING BIO-FUNCTIONS availability for plants, they provide starkly TO AGRICULTURAL SOILS Management practices that help restore sustaining microbial viability and activity. contrasting habitats for microbial life. Before being converted to agriculture, bio-functionality to agricultural soils Bruns’s team aims to learn how microbe- soils are endowed with vital stocks include reduced tillage, crop rotations with enhance the abilities of soil microbes to and little access to water and air due informed management for both of organic matter, a dark, amorphous perennial legumes, and cover cropping retain N in its less mobile forms and keep to heavy compaction by equipment. substance built up over decades, if not (Fig. 3). Winter cover crops, planted in it from being lost so quickly to the centuries, by microbial decomposition late summer or fall, add organic carbon environment. This is an important goal of plant, animal, and microbial residues. and provide a protective soil cover. Bruns for improving soil functionality, because Agricultural crop harvesting, however, and her colleagues are evaluating changes on average, less than 50% of fertilizer N is prevents most plant residues from being in soil microbial processes in response taken up by agricultural crops worldwide. returned to the soil, and tillage (e.g., to these practices in a USDA-funded plowing) disrupts and aerates soils, cropping systems experiment. RESTORING PRODUCTIVITY causing rapid microbial oxidation of TO MINING-IMPACTED LANDS organic matter. These practices, combined The Bruns group is particularly In the U.S. Appalachian region, strip with wind and water erosion, have caused interested in the relationship between mining to access near-surface coal native organic matter stocks to be lowered soil functionality and predominant forms seams has impacted millions of hectares. by half in agricultural soils worldwide. of plant-available nitrogen (N). They Although government legislation in the propose that N in its less mobile forms 1970s mandated reclamation of strip- To restore soil functionality, continued (i.e., ammonium, amino acids, proteins) mined lands, legal requirements are supply of fresh root exudates or organic predominate in well-functioning soils, based on minimum plant cover rather residues is essential. Additions of organic resulting in longer soil N residence than on soil properties, with the result Figure 1. Reduced tillage, cover cropping, matter sustain microbial degradation times and increased probability of crop that previous levels of land productivity and extended residue cover build soil Figure 3. Roots of a cover crop, organic matter and protect against erosion. of energy-rich carbon compounds to N uptake. An example of a potentially are rarely achieved post-reclamation. coated with rhizosphere soil. make mineral nutrients available to plants beneficial process under study is the Poor plant productivity persists because www.researchoutreach.org www.researchoutreach.org Whereas strip-mined lands are extensive in area, smaller “kill zones” result when Behind the Research highly acidic mine waters burst out of abandoned underground mines. As mineral-rich acid mine drainage (AMD) Mary Ann Bruns, Ph.D. emerges and flows overland, acidic metal precipitates are deposited on E: [email protected] T: +1 814 863 0779 https://ecosystems.psu.edu/directory/mvb10 http://sites.psu.edu/soilmicrobiology/photos/ the land, killing all vegetation in its wake. W: W: W: https://www.researchgate.net/profile/Maryann_Bruns A characteristic feature of a barren kill zone is a red-orange surface layer of iron oxide precipitates (below pH 3) that Research Objectives References prohibits vascular plant growth. Left unattended, kill zones remain barren for Dr Mary Ann Bruns’ work aims to learn how soil microbiome Bhowmik, Arnab, Mara Cloutier, Emily Ball, Mary Ann Bruns. 2017. Underexplored microbial metabolisms for enhanced decades, only permitting growth of acid- Figure 4. Acid mine drainage “kill zone” prior to the reclamation experiment. functions can be promoted to improve nitrogen recycling The 50-year-old barrens was created by overland flow of discharge from an nutrient recycling in agricultural soils. AIMS Microbiology 3(4): tolerant mosses or lichens. and water retention in agricultural and mined land soils. abandoned underground coal mine. 826-845. https://DOI:10.3934/microbiol.2017.4.826. Lupton, Mary Kay, Claudia Rojas, Patrick J Drohan, Mary Ann Bruns and her team have conducted Detail Bruns. 2013. Vegetation and soil development in compost- research on an accessible AMD barrens Countering expectations, all plots were CONCLUSIONS amended iron oxide precipitates at a 50-year-old acid mine in the Appalachian Plateau about 100 successfully revegetated, although To improve soil functionality, we can Mary Ann Bruns, Ph.D. drainage barrens. Restoration Ecology 21:320-328. https://doi. km from her university (Fig. 4). Most each zone supported very different make the most of resident soil microbes Associate Professor of Soil Microbiology Dept. of Ecosystem org/10.1111/j.1526-100X.2012.00902.x of the barrens is no longer inundated plant communities. Their treatment by ameliorating their living conditions, Science and Management Rojas, CR, RM Gutierrez, MA Bruns. 2016. Bacterial and eukaryal and comprises three zones differing in proved effective, even in the most providing sufficient,