Matching desert fungal community identity and function
We can know the breadth of fungal diversity by sequencing environmental samples, but how do we even begin to figure out their ecological functions? In this study, we complemented molecular characterization of aridland biological soil crust and rhizosphere fungal communities with a fungal baiting experiment to assay catabolic functions. Field crust and rhizosphere soil samples from Arches National Park were baited with recalcitrant substrates (cellulose, chitin, inositol hexaphosphate), and incubated under field ambient conditions to select for community members that utilize each substrate. Fungal hyphae and spores within the bait compartment were then harvested and used to establish single-strain cultures on similar substrate-selective media (pictured in banner). We found that fungal community composition showed strong divergence among bait types and site origin, as well as significant divergence between rhizosphere and crust communities interacting with bait type. In addition, we saw strong divergence in fungal community members of the same sample incubated for 5 months compared to a 15 month period, indicating high turnover of community composition likely related to variation in fungal growth and life history strategy. Future sequencing of single-strain cultures will match function to identity.
Collaborators: Jayne Belnap, Cheryl Kuske, Robert Sinsabaugh, Lee taylor, and Jennifer Rudgers.
Biological assays of rhizosphere microbial community change under N addition
Human activity has dramatically increased the amount of reactive N in the atmosphere and deposited onto terrestrial ecosystems, the effects of which on communities and ecosystem function are wide-ranging. Of particular importance are the effects of nitrogen deposition on soil microbial communities, which can mediate cascading geochemical and biological responses. However, most work in this sphere has focused on mesic ecosystems, and less is known about responses in arid systems where the historical sources of N input are N fixation in biological soil crusts. In this study, we investigated the effects of a field N addition experiment in Arches National Park on crust and rhizospheric microbial communities in an arid grassland, using a dominant grass as a phytometer to determine whether shifts in microbial composition affect plant performance. We found that edaphic characteristics such as soil texture were more important in driving plant-microbial interaction outcomes than the indirect effects of N deposition. Read the paper here.
Collaborators: Jayne Belnap, Cheryl Kuske, Sasha Reed, and Jennifer Rudgers.
Effects of biological soil crust disturbance on plant and arthropod communities
Biological soil crusts(biocrust) are communities of lichen, moss, and cyanobacteria that produce polysaccharides which aggregate particles. They contribute to nitrogen and hydrological cycles and prevent erosion, functions crucial to desert ecosystems. The effects of biocrusts on plant community structure remain largely unexplored, however, and even less is known about their cascading effects in consumer communities. They are also delicate micro-communities that are frequently disturbed by livestock trampling and human activities. To determine how the disturbance of biocrusts alters plant and arthropod community structure in semiarid ecosystems and connect those changes to physical, chemical, ecological, and ecosystem properties of biocrusts, we set up a fully replicated crust disturbance experiment in two ecosystems (shrubland and grassland) at the Sevilleta LTER in the spring of 2013.
Collaborators: Jennifer Rudgers, Eva Robinson, and Beth Haley.