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.
