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.