Lloret F., Sapes G., Rosas T., Galiano L., Saura-Mas S., Sala A., Martínez-Vilalta J. (2018) Non-structural carbohydrate dynamics associated with drought-induced die-off in woody species of a shrubland community. Annals of Botany. 121: 1383-1396.LinkDoi: 10.1093/aob/mcy039
Background and Aims The relationship between plant carbon economy and drought responses of co-occurring woody species can be assessed by comparing carbohydrate (C) dynamics following drought and rain periods, relating these dynamics to species' functional traits. We studied nine woody species coexisting in a continental Mediterranean shrubland that experienced severe drought effects followed by rain. Methods We measured total non-structural carbohydrates (NSC) and soluble sugars (SS) in roots and stems during drought and after an autumn rain pulse in plants exhibiting leaf loss and in undefoliated ones. We explored whether their dynamics were related to foliage recovery and functional traits (height [H], specific leaf area [SLA], wood density [WD]). Key Results During drought, NSC concentrations were overall lower in stems and roots of plants experiencing leaf loss, while SS decreases were smaller. Roots had higher NSC concentrations than stems. After the rain, NSC concentrations continued to decrease, while SS increased. Green foliage recovered after rain, particularly in plants previously experiencing higher leaf loss, independently of NSC concentrations during drought. Species with lower WD tended to have more SS during drought and lower SS increases after rain. In low-WD species, plants with severe leaf loss had lower NSC relative to undefoliated ones. No significant relationship was found between H or SLA and C content or dynamics. Conclusions Our community-level study reveals that, while responses were species-specific, C stocks overall diminished in plants affected by prolonged drought and did not increase after a pulse of seasonal rain. Dynamics were faster for SS than NSC. We found limited depletion of SS, consistent with their role in basal metabolic, transport and signalling functions. In a scenario of increased drought under climate change, NSC stocks in woody plants are expected to decrease differentially in coexisting species, with potential implications for their adaptive abilities and community dynamics. © The Author(s) 2018.
Canelles, Q., Saura-Mas, S., Brotons, L., García, M.B., Lloret, F., Villellas, J., Morris, W.F. (2017) Environmental stress effects on reproduction and sexual dimorphism in the gynodioecious species Silene acaulis. Environmental and Experimental Botany. : 0-0.LinkDoi: 10.1016/j.envexpbot.2017.06.010
De La Riva, E.G., Lloret, F., Pérez-Ramos, I.M., Marañón, T., Saura-Mas, S., Díaz-Delgado, R., Villar, R. (2017) The importance of functional diversity in the stability of Mediterranean shrubland communities after the impact of extreme climatic events. Journal of Plant Ecology. 10: 281-293.LinkDoi: 10.1093/jpe/rtw027
Lloret F., de la Riva E.G., Pérez-Ramos I.M., Marañón T., Saura-Mas S., Díaz-Delgado R., Villar R. (2016) Climatic events inducing die-off in Mediterranean shrublands: are species’ responses related to their functional traits?. Oecologia. : 1-13.LinkDoi: 10.1007/s00442-016-3550-4
Extreme climatic episodes, likely associated with climate change, often result in profound alterations of ecosystems and, particularly, in drastic events of vegetation die-off. Species attributes are expected to explain different biological responses to these environmental alterations. Here we explored how changes in plant cover and recruitment in response to an extreme climatic episode of drought and low temperatures were related to a set of functional traits (of leaves, roots and seeds) in Mediterranean shrubland species of south-west Spain. Remaining aerial green cover 2 years after the climatic event was positively related to specific leaf area (SLA), and negatively to leaf water potential, stable carbon isotope ratio and leaf proline content. However, plant cover resilience, i.e. the ability to attain pre-event values, was positively related to a syndrome of traits distinguished by a higher efficiency of water use and uptake. Thus, higher SLA and lower water-use efficiency characterized species that were able to maintain green biomass for a longer period of time but were less resilient in the medium term. There was a negative relationship between such syndromes and the number of emerging seedlings. Species with small seeds produced more seedlings per adult. Overall, recruitment was positively correlated with species die-off. This study demonstrates the relationship between plant traits and strong environmental pulses related to climate change, providing a functional interpretation of the recently reported episodes of climate-induced vegetation die-off. Our findings reveal the importance of selecting meaningful traits to interpret post-event resilience processes, particularly when combined with demographic attributes. © 2016 Springer-Verlag Berlin Heidelberg
Benejam L., Saura-Mas S., Bardina M., Sola C., Munne A., Garcia-Berthou E. (2015) Ecological impacts of small hydropower plants on headwater stream fish: From individual to community effects. Ecology of Freshwater Fish. : 0-0.LinkDoi: 10.1111/eff.12210
Hydroelectricity is increasingly used worldwide as a source of renewable energy, and many mountain ranges have dozens or hundreds of hydropower plants, with many more being under construction or planned. Although the ecological impacts of large dams are relatively well known, the effects of small hydropower plants and their weirs have been much less investigated. We studied the effects of water diversion of small hydropower plants on fish assemblages in the upper Ter river basin (Catalonia, NE Spain), which has headwater reaches with good water quality and no large dams but many of such plants. We studied fish populations and habitat features on control and impacted reaches for water diversion of 16 hydropower plants. In the impacted reaches, there was a significantly lower presence of refuges for fish, poorer habitat quality, more pools and less riffles and macrophytes, and shallower water levels. We also observed higher fish abundance, larger mean fish size and better fish condition in the control than in impacted reaches, although the results were species-specific. Accordingly, species composition was also affected, with lower relative abundance of brown trout (Salmo trutta) and Pyrenean minnow (Phoxinus bigerri) in the impacted reaches and higher presence of stone loach (Barbatula quignardi) and Mediterranean barbel (Barbus meridionalis). Our study highlights the effects of water diversion of small hydropower plants from the individual to the population and community levels but probably underestimates them, urging for further assessment and mitigation of these ecological impacts. © 2014 John Wiley & Sons A/S.
Benejam L., Saura-Mas S., Montserrat J., Torres F., Macies M. (2015) Could electric fish barriers help to manage native populations of European crayfish threatened by crayfish plague (Aphanomyces astaci)?. Management of Biological Invasions. 6: 307-310.LinkDoi: 10.3391/mbi.2015.6.3.10
Crayfish plague (Aphanomyces astaci) is the main problem that hinders the conservation of European crayfish species. Every year, dozens of native crayfish populations disappear due to this disease. We used an electric fish barrier to block the dispersal of infected crayfish upstream. One of the main objectives of this communication is to transfer our expertise using this equipment for improved conservation outcomes. As a result, we report a detailed description of the experience, as well as requirements, problems and opportunities of using an electric fish barrier to try to control crayfish plague in-situ. © 2015 The Author(s) and 2015 REABIC.
Rubio L., Bodin O., Brotons L., Saura S. (2015) Connectivity conservation priorities for individual patches evaluated in the present landscape: How durable and effective are they in the long term?. Ecography. 38: 782-791.LinkDoi: 10.1111/ecog.00935
One of the most widespread approaches for setting spatially-explicit priorities for connectivity conservation consists in evaluating the effects of the individual removal of each habitat patch (one at a time) from the landscape. It however remains unknown the degree to which such priorities are valid and reliable in the longer term, as subsequent habitat losses and other disruptions accumulate in the landscape. We compared the patch prioritizations and estimated connectivity losses resulting from individual patch removals and from a more exhaustive assessment accounting for the potentially synergistic impacts of multiple habitat losses by testing all possible combinations of patch removals. Habitat availability (reachability) metrics and metapopulation capacity were calculated in purposefully simulated landscapes and in habitat distribution data for three bird species (NE Spain). We found that 1) individual patch removals allowed identifying areas of low contribution to connectivity that remained so after subsequent network modifications, 2) the most important patches identified through individual removals often did not coincide with those patches whose removal would actually be most detrimental after multiple habitat losses. However, these differences were smaller for the habitat reachability metrics, as well as for very mobile species that were largely insensitive to habitat spatial arrangement. If many patch losses over time are likely, it might be a more robust and fruitful conservation strategy for managers to pinpoint those patches that, with a low negative impact on connectivity, can be converted to other land uses, instead of trying to elucidate through individual patch removals which subset of protected patches would be the most effective for conserving as much connectivity as possible in the long term. Individual patch removals provide useful but non-permanent guidelines that may need to be reassessed when substantial landscape modifications occur, which requires dynamic strategies for connectivity conservation in the face of global change. © 2014 The Authors.
Saura-Mas S., Bonas A., Lloret F. (2014) Plant community response to drought-induced canopy defoliation in a Mediterranean Quercus ilex forest. European Journal of Forest Research. : 0-0.LinkDoi: 10.1007/s10342-014-0848-9
Climate change has increased drought-induced tree die-off in many parts of the world, and future climate models expect a higher recurrence of these perturbations. However, few studies have addressed plant community recovery after drought events, particularly in Mediterranean forests. This study evaluates the consequences of drought-induced die-off of the dominant holm-oak (Quercus ilex) trees on composition, structure and recruitment of the plant community, 6 years after a severe drought episode in Montserrat mountain (Catalonia, NE Spain). We evaluated the relationship of the vegetation response variables to two parameters related to the die-off consequences: canopy openness, as a measure of radiation arriving to ground, and canopy defoliation weighed by plant size, as a measure of drought impact on dominant neighbor plants. We also included in our analyses topographic situation to account for the proximity to ridge summits. Six years after the drought episode, the main findings were as follows: (1) There was a general loss of canopy cover, but Q. ilex still remained as dominant; nevertheless, the small tree Phyllirea latifolia and the shrub Buxus sempervirens tended to increase its relative abundance in the upper vegetation canopy; (2) overall, in open canopy conditions, species richness was higher mostly due to the presence of shade-intolerant herbaceous plants and early successional shrubs, such as Cistus albidus; (3) die-off did not result in increasing recruitment of the dominant species but preexisting Q. ilex sprouts were taller in sites with more open canopy; (4) there was a negative relationship between weighed defoliation and understory height, including Q. ilex sprouts, that can be attributed to large drought impact to both understory and canopy holm-oaks in some microhabitats, such as sites with abundant outcrops. This study highlights the ways in which Q. ilex Mediterranean forests regenerate after drought-induced events of canopy die-off. This regeneration involves changes in community structure and composition involving the increase in species, mostly small shrubs and herbaceous plants, which are able to grow in habitats created by canopy openness, likely becoming dominant in the landscape, as well as the arrival of non-dominant shrubs and short trees to the canopy. Potential shift in vegetation may be facilitated by the lack of increasing recruitment of Q. ilex, but this may be counterbalanced by the ability of holm-oak canopy to resprout and because pre-established saplings grown more with canopy openness. Thus, if tree canopies do not recover in a certain amount of time after the drought episode, then defoliation could lead to permanent changes in diversity and composition of the community.
Saura-Mas S., Lloret F. (2014) Adult root structure of mediterranean shrubs: Relationship with post-fire regenerative syndrome. Plant Biology. 16: 147-154.LinkDoi: 10.1111/plb.12043
Life-history attributes can impose differences on root system structures and properties related to nutrient and water uptake. Here, we assess whether plants with different post-fire regenerative strategies (resprouters, seeders and seeder-resprouters) differ in the topological and morphological properties of their root systems (external path, altitude, magnitude, topological index, specific root length, root length, root-to-shoot biomass ratio, length of the main axis of the root system and link length). To achieve these objectives, we sampled individuals from eight woody species in a shrubland located in the western Mediterranean Basin. We sampled the adult root systems using manual field excavation with the aid of an air compressor. The results indicate that resprouters have a higher root-to-shoot ratio, confirming their higher ability to store water, starch and nutrients and to invest in the belowground biomass. Moreover, this pattern would allow them to explore deeper parts of the soil layers. Seeder species would benefit from a higher specific root length, pointing to increased relative root growth and water uptake rates. This study confirms that seeders and resprouters may differ in nutrient and water uptake ability according to the characteristics of their root system. Species that can both resprout and establish seedlings after fire had different patterns of root system structure; in particular, root:shoot ratio was more similar to resprouters and specific root length was closer to seeders, supporting the distinct functional performance of this type of species. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.
Saura-Mas S., Estiarte M., Peñuelas J., Lloret F. (2012) Effects of climate change on leaf litter decomposition across post-fire plant regenerative groups. Environmental and Experimental Botany. 77: 274-282.LinkDoi: 10.1016/j.envexpbot.2011.11.014
Decomposition is a determining factor for the functioning of ecosystems because litter dynamics (litter fall and litter decomposition) constitute a key process in the regulation of the recycling of carbon and nutrients. We studied the litter decomposition properties of a set of 19 Mediterranean-basin woody species with different post-fire regenerative strategies (resprouters and non-resprouters), under experimental climate manipulation (simulating warming and drought) over a 2-year period. We show that climate change modifies litter decomposition of these Mediterranean woody species as litter contributions to the soil (g/year) were lower under drought experimental conditions. Species with different post-fire regeneration performance showed different leaf decomposition patterns, though these patterns were influenced by the taxonomical affiliation of the species. As expected, the mass loss of the non-resprouter litter, after 2 years, was higher than in resprouters. Non-resprouters showed higher nutrient concentration per mass of leaf litter after 2 years of experiment than resprouters, possibly because they have lost more C-rich biomass, allowing high nutrients concentration in the remaining litter. That would apply particularly to P as litter N:P ratio was lower in non-resprouters than in resprouters. This study suggests that, in Mediterranean ecosystems, nutrients' return from leaf litter to the soil will be slower under the projected future drier conditions. Furthermore, changes in fire regimes that lead to modifications in the abundance of post-fire regenerative groups are likely to affect ecosystem's functional properties. Thus, if new fire regimes enhance non-resprouters' abundance, we can expect a greater return of organic matter contributions to the soil and a lower litter N:P. © 2011 Elsevier B.V.
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