Recently accepted articles from the lab

Four new papers from the lab have been accepted during the last weeks. These include the first paper from Cristina´s Ph.D. work (well done Cristina!), a couple of reviews on the impacts of global environmental change on drylands and on the responses of plant communities to global change drivers and soil nutrient heterogeneity and a paper on how BSC modulate different aspects of the N cycle in response to changes in temperature and moisture.

They will be published online early during the next weeks/months, but as a sneak preview here are the abstracts:

It’s getting hotter in here: determining and projecting the impacts of global environmental change on drylands

Fernando T. Maestre, Roberto Salguero-Gómez & José L. Quero

Philosophical Transactions of the Royal Society B (in press)

Drylands occupy large portions of the Earth, and are a key terrestrial biome from the socio-ecological point of view. In spite of their extent and importance, the impacts of global environmental change on them remain poorly understood. In this introduction, we review some of the main expected impacts of global change in drylands, quantify research efforts on the topic, and highlight how the articles included in this theme issue contribute to fill current gaps in our knowledge. Our literature analyses identify key understudied areas that need more research (e.g., countries like Mauritania, Mali, Burkina Faso, Chad, and Somalia, and deserts such as the Thar, Kavir and Taklamakan), and indicate that most global change research carried out to date in drylands has been done on a unidisciplinary basis. The contributions included here use a wide array of organisms (from microorganisms to humans), spatial scales (from local to global) and topics (from plant demography to poverty alleviation) to examine key issues on the socio-ecological impacts of global change in drylands. These papers highlight the complexities and difficulties associated with the prediction of such impacts. They also identify the increased use of long-term experiments and multi-disciplinary approaches as priority areas for future dryland research. Major advances on our ability to predict and understand global change impacts on drylands can be achieved by explicitly considering how the responses of individuals, populations and communities will in turn affect ecosystem services. Future research should explore linkages between these responses and their effects on water and climate, as well as the provisioning of services for human development and well-being.

 

Plant responses to soil heterogeneity and global environmental change

Pablo García-Palacios, Fernando T. Maestre, Richard D. Bardgett & Hans de Kroon

Journal of Ecology (in press)

1. Recent evidence suggests that soil nutrient heterogeneity, a ubiquitous feature of terrestrial ecosystems, modulates plant responses to ongoing global change (GC). However, we know little about the overall trends of such responses, the GC drivers involved, and the plant attributes affected.

2. We synthesized literature to answer the question: Does soil heterogeneity significantly affect plant responses to main GC drivers, such as elevated atmospheric carbon dioxide concentration (CO₂), nitrogen (N) enrichment and changes in rainfall regime?

3. Overall, most studies have addressed short-term effects of N enrichment on the performance of model plant communities using experiments conducted under controlled conditions. The role of soil heterogeneity as a modulator of plant responses to elevated CO₂ may depend on the plasticity in nutrient uptake patterns. Soil heterogeneity does interact with N enrichment to determine plant growth and nutrient status, but the outcome of this interaction has been found to be both synergistic and inhibitory. The very few studies published on interactive effects of soil heterogeneity and changes in rainfall regime prevented us from identifying any general pattern.

4. We identify the long-term consequences of soil heterogeneity on plant community dynamics in the field, and the ecosystem level responses of the soil heterogeneity × GC driver interaction, as the main knowledge gaps in this area of research.

5. In order to fill these gaps and take soil heterogeneity and GC research a step forward, we propose the following research guidelines: 1) combining morphological and physiological plant responses to soil heterogeneity with field observations of community composition and predictions from simulation models; and 2) incorporating soil heterogeneity into a trait-based response-effect framework, where plant resource-use traits are used as both response variables to this heterogeneity and GC, and predictors of ecosystem functioning.

6. Synthesis. There is enough evidence to affirm that soil heterogeneity modulates plant responses to elevated atmospheric CO₂ and N enrichment. Our synthesis indicates that we must explicitly consider soil heterogeneity to accurately predict plant responses to GC drivers.

Warming reduces the growth and diversity of biological soil crusts in a semi-arid environment: implications for ecosystem structure and functioning

Cristina Escolar,  Isabel Martínez, Matthew A. Bowker & Fernando T. Maestre

Philosophical Transactions of the Royal Society B (in press)

Biological soil crusts (BSCs) are key biotic components of dryland ecosystems worldwide that control many functional processes, including carbon and nitrogen cycling, soil stabilization, and infiltration. Regardless of their ecological importance and prevalence in drylands, very few studies have explicitly evaluated how climate change will affect the structure and composition of BSCs, and the functioning of their constituents. Using a manipulative experiment conducted over three years in a semi-arid site from central Spain, we evaluated how the composition, structure and performance of lichen-dominated BSCs respond to a 2.4 ºC increase in temperature, and to a ~ 30% reduction of total annual rainfall. In areas with well-developed BSCs, warming promoted a significant decrease in the richness and diversity of the whole BSC community. This was accompanied by important compositional changes, as the cover of lichens suffered a substantial decrease with warming (from 70% to 40% on average), while that of mosses increased slightly (from 0.3% to 7% on average). The physiological performance of the BSC community, evaluated using chlorophyll fluorescence, increased with warming during the first year of the experiment, but did not respond to rainfall reduction. Our results indicate that ongoing climate change will strongly affect the diversity and composition of BSC communities, as well as their recovery after disturbances. The expected changes in richness and composition under warming could reduce or even reverse the positive effects of BSCs on important soil processes. Thus, these changes are likely to promote an overall reduction in ecosystem processes that sustain and control nutrient cycling, soil stabilization and water dynamics.

Biological soil crusts increase the resistance of soil nitrogen dynamics to changes in temperatures in a semi-arid ecosystem

Manuel Delgado-Baquerizo, Fernando T. Maestre & Antonio Gallardo

Plant and Soil (in press)

Aims

Biological soil crusts (BSCs), composed by mosses, lichens, liverworts and cyanobacteria, are a key component of arid and semi-arid ecosystems worldwide, and play key roles modulating several aspects of the nitrogen (N) cycle, such as N fixation and mineralization. While the performance of its constituent organisms largely depends on moisture and rainfall conditions, the influence of these environmental factors on N transformations under BSC soils has not been evaluated before.

Methods

The study was done using soils collected from areas devoid of vascular plants with and without lichen-dominated BSCs from a semi-arid Stipa tenacissima grassland. Soil samples were incubated under different temperature (T) and soil water content (SWC) conditions, and changes in microbial biomass-N, dissolved organic nitrogen (DON), amino acids, ammonium, nitrate and both inorganic N were monitored. To evaluate how BSCs modulate the resistance of the soil to changes in T and SWC, we estimated the Orwin and Wardle Resistance index.

Results

The different variables studied were more affected by changes in T than by variations in SWC at both BSC-dominated and bare ground soils. However, under BSCs, a change in the dominance of N processes from a net nitrification to a net ammonification was observed at the highest SWC, regardless of T.

Conclusions

Our results suggest that the N cycle is more resistant to changes in T in BSC-dominated than in bare ground areas. They also indicate that BSCs could play a key role in minimizing the likely impacts of climate change on the dynamics of N in semi-arid environments, given the prevalence and cover of these organisms worldwide.