Oriol Grau

• Ph D
• Research Coordinator at Alt Pirineu Natural Park

Key message Inventory and seasonal variation of terpene emissions from tropical trees in French Guiana: implications for environmental and ecological roles. Abstract A limited understanding of foliar terpene emissions from different tree species is prominent in diverse tropical forests. We conducted a study in French Guiana, screening BVOC emissio...

In the valley of Espot, central Iberian Pyrenees, two congeneric species coincide in the same habitats, showing a similar encroaching ability as prostrate shrubs expanding on former rangeland. Out of this valley, however, while Juniperus communis is widespread from regional to Holarctic levels, J. sabina is only sparsely found in distant Palearctic...

Fine roots mediate plant nutrient acquisition and growth. Depending on soil nutrient availability, plants can regulate fine root biomass and morphological traits to optimise nutrient acquisition. Little is known, however, about the importance of these parameters influencing forest functioning. In this study, we measured root responses to nutrient a...

In the Pyrenees, sporadic permafrost also exists at lower altitudes, where several active rock glaciers have been also identified. In this mountain range, the presence of permafrost has been mostly detected through the mapping of geomorphological indicators (rock glaciers, protalus lobes, frost mounds, etc), bottom temperature snow measurements, ge...

The Research Observatory of the Alt Pirineu Natural Park has been admitted to the research network 'INTERACT' as Observer Station, and has become the southernmost European site. INTERACT (https://eu-interact.org/) promotes research in Arctic, Boreal and Alpine areas. It also promotes knowledge exchange in the field of terrestrial ecology and raises...

There is increasing evidence to suggest that soil nutrient availability can limit the carbon sink capacity of forests, a particularly relevant issue considering today's changing climate. This question is especially important in the tropics, where most part of the Earth's plant biomass is stored. To assess whether tropical forest growth is limited b...

Soil nutrient availability and functional traits interact in complex ways during the assembly of tree communities hindering our understanding of the implications that this may have for their phylogenetic and functional diversity. We combined abundance, taxonomic, phylogenetic and functional trait data of 222 tree species distributed along nutrient...

Rock‐derived nutrients such as calcium (Ca), magnesium (Mg), phosphorus (P), and potassium (K) are essential plant resources, yet depleted in highly weathered tropical soils, leading to nutrient limitation of productivity or other ecosystem processes. Despite this, substantial amounts of rock‐derived nutrients occur within wood, which raises questi...

Because of their steep gradients in abiotic and biotic factors, mountains offer an ideal setting to illuminate the mechanisms that underlie patterns of species distributions and community assembly. We compared the composition of taxonomically and functionally diverse fungal communities in soils along five elevational gradients in mountains of the N...

Terrestrial biosphere models typically use the biochemical model of Farquhar, von Caemmerer, and Berry (1980) to simulate photosynthesis, which requires accurate values of photosynthetic capacity of different biomes. However, data on tropical forests are sparse and highly variable due to the high species diversity, and it is still highly uncertain...

Understanding the mechanisms that drive the change of biotic assemblages over space and time is the main quest of community ecology. Assessing the relative importance of dispersal and environmental species selection in a range of organismic sizes and motilities has been a fruitful strategy. A consensus for whether spatial and environmental distance...

Terrestrial biosphere models typically use the biochemical model of Farquhar, von Caemmerer and Berry (1980) to simulate photosynthesis, which requires accurate values of photosynthetic capacity of different biomes. However, data on tropical forests are sparse and highly variable due to the high species diversity, and it is still highly uncertain h...

Production, emission, and absorption of biogenic volatile organic compounds (BVOCs) in ecosystem soils and associated impacts of nutrient availability are unclear; thus, predictions of effects of global change on source-sink dynamic under increased atmospheric N deposition and nutrition imbalances are limited. Here, we report the dynamics of soil B...

In tropical forests, free‐living Biological nitrogen (N) fixation (BNF) in soil and litter tends to decrease when substrate N concentrations increase, whereas increasing phosphorus (P) and molybdenum (Mo) soil and litter concentrations have been shown to stimulate free‐living BNF rates. Yet, very few studies explored the effects of adding N, P, and...

Ectomycorrhizal (EcM) and saprotrophic fungi interact in the breakdown of organic matter, but the mechanisms underlying the EcM role on organic matter decomposition are not totally clear. We hypothesized that the ecological relations between EcM and saprotroph fungi are modulated by resources availability and accessibility, determining decompositio...

Resorption is the active withdrawal of nutrients before leaf abscission. This mechanism represents an important strategy to maintain efficient nutrient cycling; however, resorption is poorly characterized in old-growth tropical forests growing in nutrient-poor soils. We investigated nutrient resorption from leaves in 39 tree species in two tropical...

Interés de los humedales Los humedales constituyen hábitats singulares en la alta montaña, y particularmen-te en áreas donde dominan las rocas calizas, tanto por lo abrupto del relieve como por la escasez de aguas superficiales. Solo en casos especiales, tales como fondos de circos glaciares u otros rellanos alrededor de cursos de agua, se observan...

Tropical forests are generally considered to stand upon nutrient-poor soils, but soil nutrient concentrations and availabilities can vary greatly at local scale due to topographic effects on erosion and water drainage. In this study we physically and chemically characterised the soils of 12 study plots situated along a catena with a shallow slope i...

Global climate and land use change are causing woody plant encroachment in arctic, alpine, and arid/semiarid ecosystems around the world, yet our understanding of the belowground impacts of this phenomenon is limited. We conducted a globally distributed field study of 13 alpine sites across 4 continents undergoing woody plant encroachment and sampl...

Productivity of tropical lowland moist forests is often limited by availability and functional allocation of phosphorus (P) that drives competition among tree species and becomes a key factor in determining forestall community diversity. We used non-target 31P-NMR metabolic profiling to study the foliar P-metabolism of trees of a French Guiana rain...

Aridity has increased in recent decades in the Mediterranean Basin and is projected to continue to increase in the coming decades. We studied the consequences of drought on the concentrations, stoichiometries and stocks of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in leaves, foliar litter of a three dominant woody species and soil...

Background and aims Biological fixation of atmospheric nitrogen (N2) is the main pathway for introducing N into unmanaged ecosystems. While recent estimates suggest that free-living N fixation (FLNF) accounts for the majority of N fixed in mature tropical forests, the controls governing this process are not completely understood. The aim of this st...

Tropical rainforests harbor a particularly high plant diversity. We hypothesize that potential causes underlying this high diversity should be linked to distinct overall functionality (defense and growth allocation, anti-stress mechanisms, reproduction) among the different sympatric taxa. In this study we tested the hypothesis of the existence of a...

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific r...

Aims Shrub encroachment has been reported over a large proportion of the subalpine grasslands across Europe and is expected to have an important impact on the biogeochemical cycle of these ecosystems. We investigated the stoichiometric changes in the plant-soil system along the succession (e.g. increase in encroachment from unencroached grassland t...

We observed strong positive relationships between soil properties and forest dynamics of growth and mortality across twelve primary lowland tropical forests in a phosphorus-poor region of the Guiana Shield. Average tree growth (diameter at breast height) increased from 0.81 to 2.1 mm yr⁻¹ along a soil texture gradient from 0 to 67% clay, and increa...

Theory states that tree growth in lowland tropical forests on old, weathered soils is limited by low phosphorous (P) availability. However, evidence for P limitation from nutrient manipulation experiments remains unclear, which raises the question whether trees are taking up added P. In French Guianese lowland rainforest, we measured changes in nit...

Soil fauna is a key control of the decomposition rate of leaf litter, yet its interactions with litter quality and the soil environment remain elusive. We conducted a litter decomposition experiment across different topographic levels within the landscape replicated in two rainforest sites providing natural gradients in soil fertility to test the h...

Soil fauna is a key control of the decomposition rate of leaf litter, yet its interactions with litter quality and the soil environment remain elusive. We conducted a litter decomposition experiment across different topographic levels within the landscape replicated in two rainforest sites providing natural gradients in soil fertility to test the h...

The encroachment of shrubs into grasslands is common in terrestrial ecosystems dominated by grass. Land abandonment and favourable climatic trends in recent decades have favoured the expansion of shrubs into subalpine grasslands in many mountainous regions across Europe. The advance of the succession from grassland to shrubland is expected to have...

Aim Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups rep...

Treelines are sensitive to environmental changes, but few studies provide a mechanistic approach to understand treeline dynamics based on field experiments. The aim of this study was to determine how changes in the abiotic and/or biotic conditions associated with global change affect the performance of tree seedlings (later saplings) at the treelin...

Motivation: The Tundra Trait Team (TTT) database includes field‐based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade‐offs, trait–environment relationships and environmental filtering, and trait variation...

The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem...

In the Guiana craton, large areas of tropical forest have grown and evolved over an undulant topography, result of thousand to million years of hydromorphic weathering. The effects of the resultant relief (mesotopography) on soil properties and nutrient cycling are studied using a multidisciplinary approach in Paracou and Nouragues (French Guiana)....

The Pyrenean landscape has experienced deep modifications during the last millennia even at high elevations, driven by climatic changes and anthropogenic activities. The current global change, however, forces vegetation responses more than before. The most apparent ongoing vegetation shifts respond mostly to changes in land use through shifts in th...

The increase in aridity, mainly by decreases in precipitation but also by higher temperatures, is likely the main threat to the diversity and survival of Mediterranean forests. Changes in land use, including the abandonment of extensive crop activities, mainly in mountains and remote areas, and the increases in human settlements and demand for more...

Fungi play a key role in soil-plant interactions, nutrient cycling, and carbon flow and are essential for the functioning of arctic terrestrial ecosystems. Some studies have shown that the composition of fungal communities is highly sensitive to variations in environmental conditions, but little is known about how the conditions control the role of...

Nutrients are essential for plant development, and their availability and stoichiometric ratios can influence the composition of plant communities. We investigated the possibility of the reverse influence: whether the conditions of contrasting species coexistence determine foliar element concentrations and plant stoichiometry, that is, species biog...

Climate change is increasing temperatures globally and drought in many regions. If climate change continues at its current rate, the resilience of many ecosystems will likely be exceeded, altering their structure and function. A consistent understanding of the impacts, however, remains elusive due to the difficulty of obtaining data of field studie...

Tropical forests store large amounts of biomass despite they generally grow in nutrient-poor soils, suggesting that the role of soil characteristics in the structure and dynamics of tropical forests is complex. We used data for >34 000 trees from several permanent plots in French Guiana to investigate if soil characteristics could predict the struc...

Global change impacts on biogeochemical cycles have been widely studied, but our understanding of whether the responses of plant elemental composition to global change drivers differ between above- and belowground plant organs remains incomplete. We conducted a meta-analysis of 201 reports including 1,687 observations of studies that have analyzed...

Here, we summarize the results of a study focused on the knowledge of the high mountain shrubs and their encroaching role in the National Park. We analyzed the ecological distribution and the functional traits of eight species behaving as more or less invasive, and four species locally rare and not invasive. In the most relevant species, we studied...

Climate warming can lead to changes in alpine plant species interactions through modifications in environmental conditions, which may ultimately cause drastic changes in plant communities. We explored the effects of 4 years of experimental warming with open-top chambers (OTC) on Vaccinium myrtillus performance and its interaction with neighbouring...

Arctic regions are expected to experience substantial changes in climate in the coming decades. In order to predict potential changes of Arctic vegetation, it is important to understand the distinct role of life forms of plants and of individual species in relation to plant co-existence patterns. Our aim is to investigate if three common Arctic pla...

In this paper, we analyse the spatial distribution of plant diversity in the Pyrenean area of Catalonia and Andorra, in parallel to the distribution of landscape descriptors that have been proven to be related to species distribution. We used a wide range of synthetic parameters that refer to physiography (area, main outcrops), bioclimate (length o...

The 11th Conference of the Spanish Association of Terrestrial Ecology, held in Pamplona, Spain, on 6–10 May 2013, included a symposium on alpine ecological research in the Iberian Peninsula. This session offered an excellent opportunity to assess the state and progress of alpine ecology in this region, identify knowledge gaps, and discuss further d...

Background: Climate, land-use and disturbance regimes are key drivers of treeline dynamics worldwide, but local and regional spatio-temporal patterns indicate that additional factors play an important role. Some studies suggest that shrub-tree interactions control tree seedling recruitment patterns across the treeline ecotone, but little is known a...

In mid-latitude mountains, snowbeds often consist of small, scattered alpine belt units that host many plants of high biogeographic interest. Because most snowbed species are weak competitors, it is important to study the dissemination and persistence of their seeds to better understand their population dynamics. This study analyzed the snowbed flo...

Plant growth and performance in snowbed communities are strongly influenced by the length of the growing period remaining after the snowmelt date. Under the scenario of climate change, studying the phenological responses of snowbed species to variations in snowmelt date might be crucial to understand their ability to adapt and survive under changin...

Treelines have drawn persistent research interest as they can respond markedly to climate. However, the mechanisms that determine tree seedling recruitment and the response of the forest-tundra ecotone to environmental changes remain poorly understood. We hypothesise that treeline tree seedling performance depends on the interplay between climatic...

Background: Studying how species richness varies with altitude has become an important part of investigations on mechanisms explaining regional-scale plant species diversity. Altitudinal diversity patterns are poorly known in the Pyrenees and elsewhere in the main mountain massifs in Catalonia (north-eastern Iberian Peninsula).Aim: We examine the a...

Interactions between vascular plants and bryophytes determine plant community composition in many ecosystems. Yet, little is known about the importance of interspecific differences between bryophytes with respect to their effects on vascular plants. We compared the extent to which species-specific bryophyte effects on vascular plant generative recr...

Is the Pyrenean flora well known? The western Catalan Pyrenees are still surprising. Although the flora of the Catalan Pyrenees is rather complete at regional scale, there is great heterogeneity in the knowledge at the local scale. Field work during the last years has yield interesting novelties, in relation with the great environmental diversity...

In this study we examine the process of spontaneous forestation in the subalpine Pinus uncinata domain. We focus our study on six linked issues, ranging from the diachronic comparison of the landscape through aerial imagery, the demography of Pinus uncinata populations and the response of Pinus seedlings to simulated environmental changes. The land...

Abstract How do shrubs affect treeline dynamics under simulated environmental changes in the Central Pyrenees? The aim of this study is to analyse the positive and negative interactions between Pinus un-cinata and Rhododendron ferrugineum as controlling factors of the spatio-temporal evolution of the forest-alpine grassland ecotone under varying en...

Abstract In this paper we analyse the species richness of the entire flora and of different distributional and functional subgroups in the Catalan Pyrenees along the altitudinal gradient. We used the Pyrenean data gathered in the Biodiversity Data Bank of Catalonia, which consist on more than 300,000 citations of 2,491 species of vascular plants. T...

Relative importance of positive and negative interactions between plant species may change along disturbance and resource gradients. Positive interactions are suggested to prevail in low resource, low productivity (high stress) conditions and negative interactions in high resource availability. A dwarf shrub, mountain crowberry Empetrum nigrum ssp....

In short, regeneration of Pinus uncinata above the timberline is subject to a wide range of impediments. The scarcity of seedlings beyond the sharp treeline ecotone suggests dissemination shortness, and that survival and growth are impeded by harsh winter conditions in open pasture. In this ecotone the irregular vegetation structure provides safe m...

Aim To explore species richness patterns in liverworts and mosses along a central Himalayan altitudinal gradient in Nepal (100–5500 m a.s.l.) and to compare these patterns with patterns observed for ferns and flowering plants. We also evaluate the potential importance of Rapoport’s elevational rule in explaining the observed richness patterns for l...

Collectively, the observations indicate that the overall warming of the Arctic system continued in 2007. There are some elements that are stabilizing or returning to climatological norms. These mixed tendencies illustrate the sensitivity and complexity of the Arctic System. Atmosphere: Hot spot shifts toward Europe Ocean: North Pole Temperatures at...