Showing papers by "Manuel Delgado-Baquerizo published in 2014"
TL;DR: In this paper, the authors analyzed how woody vegetation of differing cover affects plant diversity and the surrogates of multiple ecosystem processes (multifunctionality) in global drylands, and how these change with aridity.
Abstract: Aim 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. Location Two hundred and twenty-four dryland sites from all continents except Antarctica, widely differing in their environmental conditions (from arid to drysubhumid sites) and relative woody cover (from 0 to 100%). Methods 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. Results 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 humpshaped 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.
87 citations
Nicolaus Copernicus University in Toruń1, King Juan Carlos University2, University of Vermont3, University of Córdoba (Spain)4, Pablo de Olavide University5, Northern Arizona University6, University of New South Wales7, Technical University of Madrid8, National University of La Pampa9, Instituto Potosino de Investigación Científica y Tecnológica10, Universidad Técnica Particular de Loja11, University of La Serena12, University of Sfax13, Central University of Venezuela14, University of the Bío Bío15, Ferdowsi University of Mashhad16, Universidade Federal de Minas Gerais17, Ohio State University18, Université du Québec à Montréal19, National University of San Juan20, International Potato Center21, State University of Feira de Santana22, Northeast Normal University23
TL;DR: The results suggest that those sites annually receiving ~ 178 mm of rainfall will be especially sensitive to future climate changes, and may help to define appropriate conservation strategies for mitigating effects of climate change on dryland vegetation.
Abstract: Aim Geographical, climatic and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. The aim of this study was to: (1) characterize patterns of beta diversity in global drylands; (2) detect common environmental drivers of beta diversity; and (3) test for thresholds in environmental conditions driving potential shifts in plant species composition. Location Global. Methods Beta diversity was quantified in 224 dryland plant communities from 22 geographical regions on all continents except Antarctica using four complementary measures: the percentage of singletons (species occurring at only one site); Whittaker's beta diversity, β(W); a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites, β(R2); and a multivariate abundance-based metric, β(MV). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographical, climatic and soil variables. Results Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity percentage of singletons and β(W) were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance (β(R2) and β(MV) were more associated with climate variability. Interactions among soil variables, climatic factors and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Main conclusions Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving c. 178 mm of rainfall will be especially sensitive to future climate changes. These findings may help to define appropriate conservation strategies for mitigating effects of climate change on dryland vegetation.
76 citations
King Juan Carlos University1, Northern Arizona University2, University of Coimbra3, University of Córdoba (Spain)4, Technical University of Madrid5, Universidad Técnica Particular de Loja6, University of La Serena7, University of New South Wales8, Université du Québec à Montréal9, University of New England (Australia)10, Pablo de Olavide University11, Colorado State University12, University of Sfax13, University of Chile14
TL;DR: In this global-scale study on drylands, plant-plant interactions were more strongly related to functional traits of the species involved than to the environmental variables considered, so moving to a trait-based facilitation/competition approach help to predict that positive plant- plant interactions are more likely to occur for taller facilitated species in drylands.
Abstract: a b s t r a c t Plant-plant interactions are driven by environmental conditions, evolutionary relationships (ER) and the functional traits of the plants involved. However, studies addressing the relative importance of these drivers are rare, but crucial to improve our predictions of the effects of plant-plant interactions on plant communities and of how they respond to differing environmental conditions. To analyze the relative importance of - and interrelationships among - these factors as drivers of plant-plant interactions, we analyzed perennial plant co-occurrence at 106 dryland plant communities established across rainfall gra- dients in nine countries. We used structural equation modelling to disentangle the relationships between environmental conditions (aridity and soil fertility), functional traits extracted from the literature, and ER, and to assess their relative importance as drivers of the 929 pairwise plant-plant co-occurrence levels measured. Functional traits, specifically facilitated plants' height and nurse growth form, were of primary importance, and modulated the effect of the environment and ER on plant-plant interactions. Environ- mental conditions and ER were important mainly for those interactions involving woody and graminoid nurses, respectively. The relative importance of different plant-plant interaction drivers (ER, func- tional traits, and the environment) varied depending on the region considered, illustrating the difficulty
71 citations
TL;DR: In this article, the authors evaluated how climate change-induced modifications in biocrust and microbial communities indirectly affect the resistance of the N cycle in drylands to climate change and found that the change in microbial communities had a negative effect on the resistance to N cycle variables.
Abstract: Summary 1. Climate change will raise temperatures and modify precipitation patterns in drylands worldwide, affecting their structure and functioning. Despite the recognized importance of soil communities dominated by mosses, lichens and cyanobacteria (biocrusts) as a driver of nutrient cycling in drylands, little is known on how biocrusts will modulate the resistance (i.e., the amount of change caused by a disturbance) of the N cycle in response to climate change. 2. Here, we evaluate how warming (ambient vs. ~2.5 °C increase), rainfall exclusion (ambient vs. ~30% reduction in total annual rainfall) and biocrust cover (incipient vs. well-developed biocrusts) affect multiple variables linked to soil N availability (inorganic and organic N and potential net N mineralization rate) and its resistance to climate change during 4 years in a field experiment. We also evaluate how climate change-induced modifications in biocrust and microbial communities indirectly affect such resistance. 3. Biocrusts promoted the resistance of soil N availability regardless of the climatic conditions considered. However, the dynamics of N availability diverged progressively from their original conditions with warming and/or rainfall exclusion, as both treatments enhanced N availability and promoted the dominance of inorganic over organic N. In addition, the increase in fungal:bacterial ratio and the decrease in biocrust cover observed under warming had a negative indirect effect on the resistance of N cycle variables. 4. Synthesis. Our results indicate that climate change will have negative direct and indirect (i.e. through changes in biocrust and microbial communities) impacts on the resistance of the N cycle in dryland soils. While biocrusts can play an important role slowing down the impacts of climate change on the N cycle due to their positive and continued effects on the resistance of multiple variables from the N cycle, such change will progressively alter N cycling in biocrust-dominated ecosystems, enhancing both N availability and inorganic N dominance.
66 citations