Maria-Teresa Sebastià

Bio: Maria-Teresa Sebastià is an academic researcher from University of Lleida. The author has contributed to research in topics: Grassland & Species richness. The author has an hindex of 27, co-authored 67 publications receiving 3564 citations.

21st century climate change threatens mountain flora unequally across Europe

Abstract: Continental-scale assessments of 21st century global impacts of climate change on biodiversity have forecasted range contractions for many species. These coarse resolution studies are, however, of limited relevance for projecting risks to biodiversity in mountain systems, where pronounced microclimatic variation could allow species to persist locally, and are ill-suited for assessment of species-specific threat in particular regions. Here, we assess the impacts of climate change on 2632 plant species across all major European mountain ranges, using high-resolution (ca. 100 m) species samples and data expressing four future climate scenarios. Projected habitat loss is greater for species distributed at higher elevations; depending on the climate scenario, we find 36-55% of alpine species, 31-51% of subalpine species and 19-46% of montane species lose more than 80% of their suitable habitat by 2070-2100. While our high-resolution analyses consistently indicate marked levels of threat to cold-adapted mountain florae across Europe, they also reveal unequal distribution of this threat across the various mountain ranges. Impacts on florae from regions projected to undergo increased warming accompanied by decreased precipitation, such as the Pyrenees and the Eastern Austrian Alps, will likely be greater than on florae in regions where the increase in temperature is less pronounced and rainfall increases concomitantly, such as in the Norwegian Scandes and the Scottish Highlands. This suggests that change in precipitation, not only warming, plays an important role in determining the potential impacts of climate change on vegetation.

Temperature sensitivity of soil respiration rates enhanced by microbial community response

Abstract: Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.

Evenness drives consistent diversity effects in intensive grassland systems across 28 European sites

Abstract: 1 Ecological and agronomic research suggests that increased crop diversity in species-poor intensive systems may improve their provision of ecosystem services. Such general predictions can have critical importance for worldwide food production and agricultural practice but are largely untested at higher levels of diversity. 2 We propose new methodology for the design and analysis of experiments to quantify diversity-function relationships. Our methodology can quantify the relative strength of inter-specific interactions that contribute to a functional response, and can disentangle the separate contributions of species richness and relative abundance. 3 Applying our methodology to data from a common experiment at 28 European sites, we show that the above-ground biomass of four-species mixtures (two legumes and two grasses) in intensive grassland systems was consistently greater than that expected from monoculture performance, even at high productivity levels. The magnitude of this effect generally resulted in transgressive overyielding. 4 A combined analysis of first-year results across sites showed that the additional performance of mixtures was driven by the number and strength of pairwise inter-specific interactions and the evenness of the community. In general, all pairwise interactions contributed equally to the additional performance of mixtures; the grass-grass and legume-legume interactions were as strong as those between grasses and legumes. 5 The combined analysis across geographical and temporal scales in our study provides a generality of interpretation of our results that would not have been possible from individual site analyses or experimentation at a single site. 6 Our four-species agricultural grassland communities have proved a simple yet relevant model system for experimentation and development of methodology in diversity-function research. Our study establishes that principles derived from biodiversity research in extensive, semi-natural grassland systems are applicable in intensively managed grasslands with agricultural plant species.

Variations in species and functional plant diversity along climatic and grazing gradients

Abstract: Different components of biodiversity may vary independently of each other along environmental gradients giving insights into the mechanisms that regulate species coexistence. In particular, the functional diversity (FD) or the presence of rare or endemic species in natural assemblages do not necessarily increase with species diversity. We studied if different components of plant species diversity (species richness, Simpson diversity, evenness) varied similarly to FD (measured as a generalization of the Simpson index) and rarity along grazing intensity and climatic gradients. Plots under different sheep grazing regimes (high and low intensity, abandonment) were surveyed in five locations along a climatic gradient in north-eastern Spain, from semi-arid lowland to moist upland locations. Variation in species diversity, functional diversity and rarity followed different patterns. Species diversity was lowest in water-stressed environments (arid locations and southern aspects) and increased with grazing more makedly in humid locations. The FD was comparable between the most species-poor and species-rich locations and decreased with grazing in the moistest location, i.e. where species diversity markedly increased. The FD did not show a strong correlation with species richness nor with the Simpson index and less specious communities could show the highest functional diversity. The rarest species in the region were more frequently found in the abandoned areas, which held the lowest species diversity. Consequently, the mechanisms that enhance the diversity of species do not necessarily support a functional differentiation among those species or the maintenance of rare species in a region. We hypothesize that the degree of dependence of functional diversity on species diversity might be mostly related to the amplitude of the species' traits pool and on how species partition the niche space available.

Partitioning of functional diversity reveals the scale and extent of trait convergence and divergence

Abstract: Questions: Trait differentiation among species occurs at different spatial scales within a region. How does the partitioning of functional diversity help to identify different community assembly mechanisms? Location: Northeastern Spain. Methods: Functional diversity can be partitioned into within-community (α) and among-communities (β) components, in analogy to Whittaker's classical α and β species diversity concept. In light of ecological null models, we test and discuss two algorithms as a framework to measure α and β functional diversity (the Rao quadratic entropy index and the variance of trait values). Species and trait (specific leaf area) data from pastures under different climatic conditions in NE Spain are used as a case study. Results: The proposed indices show different mathematical properties but similarly account for the spatial components of functional diversity. For all vegetation types along the climatic gradient, the observed α functional diversity was lower than expected at random, an observation consistent with the hypothesis of trait convergence resulting from habitat filtering. On the other hand, our data exhibited a remarkably higher functional diversity within communities compared to among communities (α≫β). In contrast to the high species turnover, there was a limited functional diversity turnover among communities, and a large part of the trait divergence occurred among coexisting species. Conclusions: Partitioning functional diversity within and among communities revealed that both trait convergence and divergence occur in the formation of assemblages from the local species pool. A considerable trait convergence exists at the regional scale in spite of changes in species composition, suggesting the existence of ecological redundancy among communities.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Modern Applied Statistics With S

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Biodiversity and Ecosystem Functioning

Abstract: Species diversity is a major determinant of ecosystem productivity, stability, invasibility, and nutrient dynamics. Hundreds of studies spanning terrestrial, aquatic, and marine ecosystems show that high-diversity mixtures are approximately twice as productive as monocultures of the same species and that this difference increases through time. These impacts of higher diversity have multiple causes, including interspecific complementarity, greater use of limiting resources, decreased herbivory and disease, and nutrient-cycling feedbacks that increase nutrient stores and supply rates over the long term. These experimentally observed effects of diversity are consistent with predictions based on a variety of theories that share a common feature: All have trade-off-based mechanisms that allow long-term coexistence of many different competing species. Diversity loss has an effect as great as, or greater than, the effects of herbivory, fire, drought, nitrogen addition, elevated CO2, and other drivers of environm...

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

Abstract: B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

Facilitation in plant communities: the past, the present, and the future

Abstract: Summary 1 Once neglected, the role of facilitative interactions in plant communities has received considerable attention in the last two decades, and is now widely recognized It is timely to consider the progress made by research in this field 2 We review the development of plant facilitation research, focusing on the history of the field, the relationship between plant‐plant interactions and environmental severity gradients, and attempts to integrate facilitation into mainstream ecological theory We then consider future directions for facilitation research 3 With respect to our fundamental understanding of plant facilitation, clarification of the relationship between interactions and environmental gradients is central for further progress, and necessitates the design and implementation of experiments that move beyond the clear limitations of previous studies 4 There is substantial scope for exploring indirect facilitative effects in plant communities, including their impacts on diversity and evolution, and future studies should connect the degree of non-transitivity in plant competitive networks to community diversity and facilitative promotion of species coexistence, and explore how the role of indirect facilitation varies with environmental severity 5 Certain ecological modelling approaches (eg individual-based modelling), although thus far largely neglected, provide highly useful tools for exploring these fundamental processes 6 Evolutionary responses might result from facilitative interactions, and consideration of facilitation might lead to re-assessment of the evolution of plant growth forms