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

Background/Question/Methods
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. 

Results/Conclusions
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

Background/Question/Methods
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.

Results/Conclusions
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

Background/Question/Methods
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.

Results/Conclusions
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

Background/Question/Methods
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.

Results/Conclusions
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

Background/Question/Methods
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.

Results/Conclusions
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.