Wednesday, November 26, 2014

New Paper:Mycorrhizal phenotypes and the Law of the Minimum

Nancy Collins Johnson1,*, Gail W. T. Wilson2, Jacqueline A. Wilson2, R. Michael Millerand Matthew A. Bowker4


New Phytologist DOI:10.1111/nph.13172

  • arbuscular mycorrhizas;context dependency;light;mutualism;nitrogen (N);parasitism;phosphorus (P);stoichiometry

  • Mycorrhizal phenotypes arise from interactions among plant and fungal genotypes and the environment. Differences in the stoichiometry and uptake capacity of fungi and plants make arbuscular mycorrhizal (AM) fungi inherently more nitrogen (N) limited and less phosphorus (P) limited than their host plants. Mutualistic phenotypes are most likely in P-limited systems and commensal or parasitic phenotypes in N-limited systems. Carbon (C) limitation is expected to cause phenotypes to shift from mutualism to commensalism and even parasitism.
  • Two experiments compared the influence of fertilizer and shade on mycorrhizas in Andropogon gerardii across three naturally N-limited or P-limited grasslands. A third experiment examined the interactive effects of N and P enrichment and shade on A. gerardii mycorrhizas.
  • Our experiments generated the full spectrum of mycorrhizal phenotypes. These findings support the hypothesis that mutualism is likely in P-limited systems and commensalism or parasitism is likely in N-limited systems. Furthermore, shade decreased C-assimilation and generated less mutualistic mycorrhizal phenotypes with reduced plant and fungal biomass.
  • Soil fertility is a key controller of mycorrhizal costs and benefits and the Law of the Minimum is a useful predictor of mycorrhizal phenotype. In our experimental grasslands arbuscular mycorrhizas can ameliorate P-limitation but not N-limitation.

Thursday, November 13, 2014

Kyle Doherty's Thesis Defense: True life confessions of a moss farmer

Come hear Kyle Doherty (M.S. Biology Student)
defend his thesis:

9:30 AM, ARD Building, Large Pod, 
Northern Arizona University.

Monday, November 10, 2014

Job opening in the lab

Soil Ecology Research Technician
We are recruiting a hardworking, dedicated individual to work as a field and lab technician in soil ecology. This position will assist a Ph.D. student, Michael Remke, in preparing for a field based climate manipulation experiment in soil and plant ecology, in addition to assisting with other projects as needed. 

Position Description
The primary duties of this position will relate to soil sterilization and data collection. Additional duties will include preparing field sites for planting and transplanting pots from the NAU research greenhouse to the field. Duties will extend into the summer and will shift to data collection and monitoring at the field sites. The position allows for dedicated individuals to gain valuable research experience during the summer months. This experiment manipulates soil origin, soil organism communities, temperature and precipitation to better understand responses of a common native grass, Bouteloua gracilis, and Ponderosa Pine to climate change.

Other duties may include microscopy, chemical analyses, and maintenance of greenhouse experiments. 

Applicant should be pursuing or have completed a degree in forestry, biology, environmental studies or related field. A strong interest in soil and plant ecology research is preferred. Willingness to travel to field sites within Arizona, possibly during weekends is a must. The successful applicant must be self-motivated and able to work independently. Attention to detail and ability to maintain a clean, sterile work place are essential for success. The applicant must be physically fit and able to work in field conditions with variable weather. This position requires lifting heavy objects, shoveling, crouching, and moving heavy items. This position also requires ability to collect and manage large amounts of data. In addition, the applicant must complete NAU’s driver training and will be expected to operate large trucks on rough, remote roads. Ability to operate and navigate using topographic maps and handheld GPS units is preferred. The applicant will be trained in all appropriate methodology and will be able to work closely with graduate students while gaining valuable experience in experimental design and set up of field based soil ecology experiments.

Position Dates:
January –  August; possibility for extension into Fall
Hours: Variable (up to 20 hours per week) – potential for more at certain times
Pay: $13.00/hr
This position is not benefit eligible.
Contact Information
For more information or to apply, please contact or send a resume to:
Michael Remke:  
And please cc Dr. Matthew Bowker:

Sunday, November 2, 2014

Monday, October 20, 2014

Biochar Research

Biochar Research   October 15, 2014



Here are some photos of the romaine lettuce and beets growing in a pot containing 0%, 4% , or 8% biochar by volume.  So far everything is right on track and I will initiate the drought simulation on the seedlings in the next week.    

Sunday, October 5, 2014

Biocrust at Hovenweep NM

I traveled to Hovenweep National Monument today in search of cliff dwellings, but got distracted by the excellent crust communities there!
The lichens were especially vibrant. 
This often overlooked Monument is a great destination for those interested in the natural and cultural resources of the Southwest.  

Wednesday, September 24, 2014

New Paper: Community properties and spatial pattern effects in lichens on soil microbes

Andrea Castillo-Monroy

Aspects of soil lichen biodiversity and aggregation interact
to influence subsurface microbial function. Plant SoilDOI 10.1007/s11104-014-2256-9

Andrea P. Castillo-Monroy & Matthew A. Bowker &
Pablo García-Palacios & Fernando T. Maestre

Background and aims
Many previous studies have evaluated aboveground–heterotrophic belowground interactions such as plant-soil feedbacks, plant-mycorrhizal fungi associations or plant-actinorhizal symbioses. However, few studies have used biocrusts, which are specialized soil communities of autotrophic cyanobacteria, mosses, lichens and non-photosynthetic fungi and bacteria that are prevalent in drylands worldwide. These communities largely influence ecosystem functioning, and can be used as a model system for studying above-belowground interactions. In this study, we evaluated how biocrusts affect the functional diversity and biomass of microbial diversities beneath biocrusts.

Methods We performed two microcosm experiments using biocrust-forming lichens where we manipulated their biotic attributes to test independently the effects of species richness (from two to eight species), composition, evenness (maximal and low evenness) and spatial pattern (clumped and random distribution) on the microbial catabolic profile and microbial functional diversity.

Results Microcosms with a random pattern had a higher microbial catabolic profile than those with a clumped pattern. Significant richness × evenness × pattern and richness × evenness interactions were found when analyzing microbial catabolic profile and biomass, respectively. Microcosms with a random pattern, intermediate number of species, and maximal evenness level had higher microbial catabolic profile. At the maximal evenness level, assemblages had higher microbial catabolic
profile and microbial biomass when they contained four species. The richness × evenness × pattern interaction was the most informative predictor of variations in microbial catabolic profile.

Conclusions Our results indicate that soil microorganisms are influenced by biocrusts, just as they are influenced by plants, and highlight the importance of higher order interactions among species richness, evenness, and spatial pattern as drivers of microbial communities. The results also emphasize the importance of studying several biotic attributes simultaneously when studying biocrust-soil microorganism interactions, as in nature, community properties do not exert their influence in isolation.

Tuesday, September 23, 2014

Geodermatophilia: Biocrusts in the New York Times

Read about the work of our collaborators Ferran Garcia-Pichel, Jayne Belnap, and Sergio Velasco here...

Geodermatophilia: Biocrusts in the New York Times: A nice article by Henry Fountain ab...

Saturday, September 20, 2014

New paper on effects of woody plant dominance in drylands

Santi Soliveres, University of Bern, Switzerland
  • Santiago Soliveres, Fernando T. Maestre, David J. Eldridge, Manuel Delgado-Baquerizo, José Luis Quero, Matthew A. Bowker and Antonio Gallardo

The global spread of woody plants into grasslands is predicted to increase over the coming century. While there is general agreement regarding the anthropogenic causes of this phenomenon, its ecological consequences are less certain. We analysed how woody vegetation of differing cover affects plant diversity (richness and evenness) and the surrogates of multiple ecosystem processes (multifunctionality) in global drylands, and how these change with aridity.
Two hundred and twenty-four dryland sites from all continents except Antarctica, widely differing in their environmental conditions (from arid to dry-subhumid sites) and relative woody cover (from 0 to 100%).
Using a standardized field survey, we measured the cover, richness and evenness of perennial vegetation. At each site, we measured 14 soil variables related to fertility and the build-up of nutrient pools. These variables are critical for maintaining ecosystem functioning in drylands.
Species richness and ecosystem multifunctionality were strongly related to woody vegetation, with both variables peaking at a relative woody cover (RWC) of 41–60%. This relationship shifted with aridity. We observed linear positive effects of RWC in dry-subhumid sites. These positive trends shifted to hump-shaped RWC–diversity and multifunctionality relationships under semi-arid environments. Finally, hump-shaped (richness, evenness) or linear negative (multifunctionality) effects of RWC were found under the most arid conditions.
Main conclusions

Plant diversity and multifunctionality peaked at intermediate levels of woody cover, although this relationship became increasingly positive in wetter environments. This comprehensive study accounts for multiple ecosystem attributes across a range of levels of woody cover and environmental conditions. Our results help us to reconcile contrasting views of woody encroachment found in the current literature and can be used to improve predictions of the likely effects of encroachment on biodiversity and ecosystem services.

Friday, August 8, 2014

EvaluationHelp: Here are e the original 16 models published by Sew...

A glimpse of the dawn of structural equation modeling

EvaluationHelp: Here are e the original 16 models published by Sew...: Here are e the original 16 models published by Sewall Wright in 1921 in Journal of agricultural research. Enjoy! PS: He wasn't a '...

Friday, August 1, 2014

Congrats to Harlan Tso for completing the summer REU program in our lab

REU Scholar Harlan Tso at this morning's poster presentation

A version of the poster you can read (click to enlarge)

Geodermatophilia: Biological soil crust science forum, August 6, Kan...

Geodermatophilia: Biological soil crust science forum, August 6, Kan...: Grand Staircase-Escalante National Monument is preparing an Environmental Impact Statement on their grazing plan. Previously there was a sco...

Monday, July 28, 2014

Bowker lab - check us out at ESA next month

Next month lab members will present new research at the Ecological Society of America Meeting in Sacramento. Kyle Doherty will talk about his Master's research in moss farming. I will do a talk for Anita Antoninka (she couldn't make the trip) on her experiments in biocrust cultivation. Future lab member Kristina Young will also be giving a talk related to biocrust mosses and their susceptibility to climate change. I will coauthor a talk given by Nancy Johnson on mycorrhizal phenotypes, and both Anita and I will coauthor a talk by Laura Hagenauer on tree canopy arthropod communities.

Biocrust mosses from diverse localities exhibit plastic response to watering and may be successfully cultivated ex situ

Tuesday, August 12, 2014: 2:50 PM
315, Sacramento Convention Center

Kyle D. Doherty, Biology, Northern Arizona University, Flagstaff, AZ
Matthew Bowker , School of Forestry, Northern Arizona University, Flagstaff, AZ
Nancy C. Johnson , Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ
Anita J. Antoninka , School of Forestry, Northern Arizona University, Flagstaff, AZ
Troy Wood , Colorado Plateau Research Station, U.S. Geological Survey, Flagstaff, AZ

Wide-scale restoration of biocrust, a living matrix of soil-dwelling dust and nutrient fixers, could mitigate dust storms, and resulting deposition on snowpack, which threatens quality of life, safety, and water supplies in arid regions.  Mosses are common and vital members in many biocrust communities.  We investigated feasibility and means to optimally grow a widespread biocrust moss, Syntrichia ruralis, in a greenhouse setting.  We cultivated five populations collected from across the Colorado Plateau.  The collections captured a precipitation modality gradient along which some mosses received the majority of their water from snowmelt, while others saw the majority in the form of summer monsoon rains.  We subjected all populations to four different watering treatments, varying in duration of hydration from 2 days to 5 days weekly.  We hypothesized that mosses collected from sites that primarily received water from snowmelt would be most successful under a longer hydration scenario, and that there would be a point of diminishing returns where additional water inputs would not yield more moss tissue.  Homogenized tissue from each population was inoculated on sterilized sand and we recorded percent cover of the resulting growth over a five-month period. 

By two months we observed differences between populations.  The population that had previously received the most moisture from snowmelt had achieved greatest cover irrespective of hydration length.  The more monsoonal populations achieved lesser cover.  By four months, cover was comparable across all populations; the monsoonal populations had caught up.  Data from the four watering treatments revealed optimal moss cover developed when tissues were subjected to three consecutive days of hydration per week.   Substantial cyanobacterial and other microbial cover also developed over the course of the experiment, with increasing water inputs leading to greater total biocrust cover.  Non-metric multidimensional scaling revealed cover of microorganisms unique to certain populations of moss.   We demonstrated that mosses are plastic in their ability to adapt to a watering modality of continuous hydration.  Our data suggest that Syntichia ruralis may be sourced from diverse localities and increased off site via this method.  Initial differences in growth rates may be attributed to starting tissue quality.  Interestingly, site-specific associates may be cultivated from moss propagules.  Further study of stressful watering modalities, mimicking the brief hydration of monsoon rains, could evaluate the resiliency of populations to climate change, and the potential for assisted migration of biocrust mosses.

Rapid cultivation of desert mosses as a biological soil crust restoration material

Wednesday, August 13, 2014: 4:20 PM
315, Sacramento Convention Center
Anita J. Antoninka , School of Forestry, Northern Arizona University, Flagstaff, AZ
Matthew Bowker, School of Forestry, Northern Arizona University, Flagstaff, AZ
Kyle Doherty , School of Forestry, Northern Arizona University, Flagstaff, AZ

Desert mosses are often overlooked as an important component of desert and biological soil crusts (biocrust) ecosystems, yet they provide key ecosystem services, including soil stabilization, water retention, carbon fixation, and house N-fixing cyanobacteria on their leaves. They respond extremely rapidly to precipitation and are able to survive long periods of no water, shifting from a dormant, and desiccation tolerant state, to active photosynthesis in a matter of seconds. With these qualities, desert mosses have the potential to be an excellent desert restoration material. Our goal was to determine the best methods to cultivate Syntricia caninervis and S. ruralis, common, and abundant species in the western deserts, collected from Hill AFB near Tooele, Utah. We washed, dried and crumbled mosses, adding about 4% total surface area of one moss species to pots containing sterile sand. In a full factorial design, pots were watered from below to the saturation point continuously for 5, 4, 3, or 2 days, and given a full nutrient suite (Knop’s solution) once at the beginning, monthly or biweekly, or not at all (n=6). Using a mixture of percent cover and modified NDVI photography, we quantified growth and turnover over four months.

Moss biomass increased six-fold for both species in four months and grew best with monthly fertilizer. S. caninervis (the more drought-tolerant species) preferred 2-3 days of hydration, whereas S. ruralis (found in more mesic conditions), preferred 4-5 days hydration. Remarkably, we also cultivated a variety of other important biocrust organisms, including 4 genera of cyanobacteria, and 5 species of lichens. All were most common in S. caninervis pots, likely because this species grows very close to the ground surface, making it difficult to clean away all soil. The cyanobacterial community showed interesting patterns in turnover, withMicrocoleous spp. (~8% maximum cover) dominating early, and Nostoc spp. (~85%) dominating after month two. We also witnessed an increase in Scytonema spp. (~8%) after month three, along with a marked increase in lichen cover (~4%). All cyanobacteria grew better in S. caninervis pots, with 3-5 days hydration and biweekly fertilizer, whereas lichens showed no water/fertilizer preferences. Our results indicate that we can target and cultivate not only desert mosses, but also many biocrust organisms of interest by optimizing growing conditions. These results have great potential for scaling-up as a desert inoculum source.

Mycorrhizal phenotypes and the Law of the Minimum

Wednesday, August 13, 2014: 4:20 PM
306, Sacramento Convention Center
Nancy C. Johnson, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ
Gail W.T. Wilson , Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK
R. Michael Miller , Biosciences Division, Argonne National Laboratory, Lemont, IL
Matthew Bowker , School of Forestry, Northern Arizona University, Flagstaff, AZ

Although mycorrhizas are generally mutually beneficial for both plants and fungi, many factors influence the symbiotic outcome of mycorrhizal associations; consequently mycorrhizal function forms a continuum from mutualism to parasitism. The location of a particular mycorrhizal symbiosis on this continuum can be considered its phenotype: an emergent property of interactions among plant and fungal genotypes and the environment. Soil fertility is a key environmental controller of mycorrhizal phenotypes. Mycorrhizas can be studied using an economic perspective, photosynthate and minerals are the commodities exchanged and the trade value of these resources is set by their availability in the environment. The ‘Law of the Minimum’ states that plant production may be controlled by a single essential resource that is in limiting supply. Determining 1) which resources are in limiting supply in the environment, and 2) whether mycorrhizal symbioses can enhance access to these resources, provides an ecologically and evolutionarily sound approach to predicting mycorrhizal function in ecosystems and their responses to environmental disturbances. We explore the usefulness of this approach in a series of experiments that manipulate availability of photosynthate, nitrogen, and phosphorus to test hypothesized consequences of the Law of the Minimum to allocation patterns and functioning of arbuscular mycorrhizal associations.

Manipulation of carbon, N and P availability using shade, CO2 enrichment, and fertilization experiments generated the full spectrum of mycorrhizal phenotypes, from mutualism to commensalism to parasitism. Our findings support the hypothesis that shade decreases and CO2 enrichment increases the production of photosynthate, and that this carbon currency ultimately drives mycorrhizal trading partnerships. Also, our results show that P-limitation is a strong predictor of plant benefit from AM symbioses and that P-enrichment diminishes this benefit. The influence of N-availability on mycorrhizal phenotypes is mediated by P-availability. In systems with ample photosynthate and dual N- and P-limitation, N-enrichment increases fungal biomass and may or may not generate biomass gain for host plants. This N-induced enhancement of AM fungal biomass disappears if P is not in limited supply. Responses of AM fungi to N and P fertilization in field experiments throughout the world follow these patterns, and thus indicate that the Law of the Minimum is a useful predictor of mycorrhizal phenotype.

Seasonal dynamics in the assembly of arthropod community structure and trophic structure

Thursday, August 14, 2014: 4:00 PM
Regency Blrm B, Hyatt Regency Hotel
Laura E. Hagenauer, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ
Anita J. Antoninka , School of Forestry, Northern Arizona University, Flagstaff, AZ
Matthew A. Bowker , School of Forestry, Northern Arizona University, Flagstaff, AZ
Nancy C. Johnson , Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ

Temporal dynamics over a growing season are an integral part of arthropod community assembly patterns. We examined the hypothesis that arthropod trophic constraints follow predictable patterns over a growing season in an extremely hot, managed riparian stand of a foundation tree species, Populus fremontii. We believe that these trophic constraints will often help predict community assembly across seasons. While these patterns have been established in more moderate environments with shorter growing seasons, it is unknown how arthropods respond to a long growing season with extreme temperatures (>49 C) occurring in summer months. We found an ideal sampling system in the Fremont cottonwood (P. fremontii) trees planted for riparian habitat restoration on the Cibola National Wildlife Refuge, AZ. Our study measured the assembly of canopy arthropod communities across a growing season by monthly sampling of a consistent set of cotton wood trees with nondestructive visual techniques for 12 months. We used structural equation modeling to compare the effects of several factors thought to be important to arthropod community assembly and trophic levels including tree genetics, temperature, canopy cover, and wind speed.

We found two main patterns. 1. Arthropod trophic structure followed similar patterns as those found in milder environments with shorter growing seasons, and these patterns extended proportionately over the 10 month growing season. Herbivores were most abundant in the early months of the year, predators became more numerous in the hot summer months and then a new group of herbivores dominated the community in the final few months. 2. Our structural equation models indicate that the importance of factors affecting community assembly vary among trophic levels. We conclude that many arthropod communities may follow similar seasonal assembly rules, regardless of environmental or seasonal variation. These results argue that, while we need more information to predict arthropod community assemblage and trophic structure, sampling time may be one of the most important factors driving the patterns we find. Therefore, initial surveys to understand these dynamics are important before making broad statements about community patterns.

Dryland responses to climate change: Assessing the biogeochemical consequences of Syntrichia caninervis mortality resulting from altered precipitation regimes

Friday, August 15, 2014: 10:30 AM
302/303, Sacramento Convention Center
Kristina Young , Southwest Biological Science Center, U.S. Geological Survey, Moab, UT
Jayne Belnap , Southwest Biological Science Center, U.S. Geological Survey, Moab, UT
Sasha C. Reed , Southwest Biological Science Center, U.S. Geological Survey, Moab, UT

Biological soil crusts-a community of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface of many drylands-are a fundamental component of arid and semiarid ecosystems. These photosynthetic soil communities play critical roles in dryand function; for example, carbon fixation, nitrogen fixation, and soil stabilization – and existing data suggest biocrusts can be quite sensitive to seemingly subtle changes in climate. In particular, previous research on the Colorado Plateau showed dramatic mortality of the common moss Syntrichia caninervis in response to altered precipitation treatments:Increased frequency of 1.2mm monsoonal rainfall events reduced moss cover from >25% to <2% after only one growing season. Yet our understanding of the ecosystem consequences of these large changes to the system remain notably poor. Here we explore how the moss mortality affects belowground biogeochemistry over the course of the lethal stress. Twice weekly for 5 months we added 1.2mm of simulated rainfall to S. caninervis, as well as maintained control mosses. Throughout the experiment, we assessed the soils beneath the moss for multiple forms of carbon, nitrogen and phosphorus; nitrogen mineralization rates; and aspects of moss photosynthetic capacity (Fv/Fm) to explore how belowground biogeochemistry is affected over the course of the mortality event.

As expected, mosses were strongly, negatively affected by the increased frequency of small rainfall events. In concert with declining moss health, we found significant changes to soil biogeochemical cycling. For instance, during the first week of treatments we observed an increase in extractable NH4+ from soils associated with the stressed moss compared with the controls, however, this pattern switched such that soil extractable NH4+ for stressed moss was much lower than controls as moss decline progressed. In contrast, extractable NO3- remained elevated in the treated moss relative to controls until the last sampling event when no significant difference was observed. These patterns match well with assessments of nitrification rates, which showed nitrification was consistently elevated in soils beneath stressed moss relative to controls. In addition, the moss physiological decline was associated with a reduction in total available nitrogen and with changes in soil carbon chemistry. Taken together, our data suggest the stress mosses experience in response to altered precipitation results in significant changes to soil biogeochemical cycling. Due to the nature of these shifts, the data have important implications for soil fertility, as well as for the trajectory of biocrust recovery after the loss of a dominant community member.

Bowker Soil Ecology Lab, Northern Arizona University - Launching our new lab website

Welcome to our new website devoted to highlighting the people and research of the forest-rangeland soil ecology lab at the School of Forestry of Northern Arizona University. We are mostly a group of community and ecosystem ecologists, many of us with a strong interest in restoration ecology. Mostly we focus on soil organisms, but we are also plant ecologists. Our collective taxonomic specialties include biocrusts, mycorrhizal fungi, soil fauna, and vascular plants. Our subject matter is ecosystem functioning of soils, plant-soil interactions, biodiversity, development of restoration technologies, and empirical tests of community ecology theory. Much of our work is applied toward solving real world problems such as combatting soil erosion or plant invasions, enhancing agricultural sol fertility using forest waste, or providing the research background to inform assisted migration of plants. Above all, we like dirt and the biota that call it home.

Much of the content is currently under construction, but our plan is to maintain a blog as an active part of the website. This post kicks off the blog...please check back for updated content

Ceratodon purpureus, a.k.a. fire moss, grows on charcoal form a recent forest fire.