Geology topics

Jennifer A. Rudgers

Publications and source records attributed to Jennifer A. Rudgers.

3 recordsLinked to original sources

USGS2020

What could explain δ13C signatures in biocrust cyanobacteria of drylands?

Dryland ecosystems are increasing in geographic extent and contribute greatly to interannual variability in global carbon dynamics. Disentangling interactions among dominant primary producers, including plants and autotrophic microbes, can help partition their contributions to dryland C dynamics. We measured the δ 13 C signatures of biological soil crust cyanobacteria and dominant plant species (C 3 and C 4 ) across a regional scale in the southwestern USA to determine if biocrust cyanobacteria were coupled to plant productivity (using plant-derived C mixotrophically), or independent of plant activity (and therefore purely autotrophic). Cyanobacterial assemblages located next to all C 3 plants and one C 4 species had consistently more negative δ 13 C (by 2‰) than the cyanobacteria collected from plant interspaces or adjacent to two C 4 Bouteloua grass species. The differences among cyanobacterial assemblages in δ 13 C could not be explained by cyanobacterial community composition, photosynthetic capacity, or any measured leaf or root characteristics (all slopes not different from zero). Thus, microsite differences in abiotic conditions near plants, rather than biotic interactions, remain a likely mechanism underlying the observed δ 13 C patterns to be tested experimentally.

New Mexico↗

USGS2018

Are fungal networks key to dryland primary production?

In low-resource ecosystems, competition among primary producers can be reduced through the partitioning of limiting resources in space or time. Partitioning, coupled with species interactions, can be a source of ecosystem stability by retaining resources within a biotic “loop” and slowing losses due to physical processes, such as erosion, gaseous loss, or leaching. Such coupling occurs in marine food webs (the microbial loop), where positive interactions among microbes limit losses of nutrients that would otherwise drop to the ocean floor (Fenchel, 2008). Likewise, mycorrhizal fungi in tropical rainforests may rapidly recycle litter nutrients back to canopy trees, preventing leaching driven by high rainfall (Hattenschwiler et al., 2011). Such dynamics differ from the paradigm for most mesic, terrestrial ecosystems, in which the primary source of nutrients for primary production is the decomposition of soil organic matter (SOM, Schimel and Bennett, 2004). Thus, in ecosystems that lack large reserves of soil organic matter to supply nutrients to producers (e.g., drylands, where sparse litter yields low SOM), biotic retention of nutrients may be particularly critical to primary production and ecosystem dynamics.

American Journal of Botany↗

USGS2017

Spatial variation in edaphic characteristics is a stronger control than nitrogen inputs in regulating soil microbial effects on a desert grass

Increased atmospheric nitrogen (N) deposition can have wide-ranging effects on plant community structure and ecosystem function, some of which may be indirectly mediated by soil microbial responses to an altered biogeochemical environment. In this study, soils from a field N fertilization experiment that spanned a soil texture gradient were used as inocula in the greenhouse to assess the indirect effects of soil microbial communities on growth of a desert grass. Plant performance and interaction with soil microbiota were evaluated via plant above- and belowground biomass, leaf N concentration, and root fungal colonization. Nitrogen fertilization in the field increased the benefits of soil microbial inoculation to plant leaf N concentration, but did not alter the effect of soil microbes on plant growth. Plant-microbe interaction outcomes differed most strongly among sites with different soil textures, where the soil microbial community from the sandiest site was most beneficial to host plant growth. The findings of this study suggest that in a desert grassland, increases in atmospheric N deposition may exert a more subtle influence on plant-microbe interactions by altering plant nutrient status, whereas edaphic factors can alter the whole-plant growth response to soil microbial associates.

Journal of Arid Environments↗