J. Bosco Imbert

Drift and benthic invertebrate responses to stepwise and abrupt increases in non-scouring flow

We conducted two experiments to assess drift and benthic invertebrate responses to stepwise and abrupt changes in non-scouring flow in gravel-bed experimental streams. Intuitively, a stepwise flow increase should allow aquatic invertebrates more time to seek refuges than would an abrupt increase. We hypothesized that abrupt flow increases would result in larger increases in taxon richness and in the number of invertebrates in the drift, and a larger decrease in benthic density than would stepwise flow increases. Two kinds of drift response to flow increases were observed in the stepwise experiment: (1) no response (e.g. Caenissp. [Ephemeroptera] and Sphaeriidae [Pelecypoda]); (2) threshold response of some aquatic (e.g. Crangonyx pseudogracilis[Amphipoda]) and semiaquatic (e.g. Ormosiasp. [Diptera]) taxa. Drift richness and drift density in both experiments declined after reaching a peak. The peak was reached almost immediately in the abrupt treatment and later in the stepwise treatment. Maximum richness of taxa and taxon composition in the drift were similar in both experiments. Despite significant increases in drift, stepwise and abrupt increases in flow did not have a significant effect on benthic density. However, relative to reference streams, the percentage of total benthic invertebrates in the drift increased 10× in the stepwise experiment and 33× in the abrupt experiment. These non-scouring increases in flow were non-trivial. Our results suggest that several high flow events of the same magnitude (i.e. 2.5–3.0 fold increases) may cause considerable losses of benthic populations to the drift. The rate of increases in flow appears to be important: abrupt increases in flow had a stronger effect on invertebrate drift than did stepwise increases.

Thinning affects nutrient resorption and nutrient‐use efficiency in two Pinus sylvestris stands in the Pyrenees

Needle chemical composition was measured, and nutrient resorption, nutrient-use efficiency (NUE), and other indexes were estimated for 24 months in two contrasting natural Pinus sylvestris L. forests in the western Pyrenees in Spain. For each location (Aspurz, 650 m elevation, 7% slope; Garde, 1335 m elevation, 40% slope), there were three reference plots (P0), three plots with 20% of the basal area removed (P20), and three with 30% of the basal area removed (P30). Needle P, Ca, and Mg concentrations were higher in Garde, but N concentration was higher for Aspurz, without differences for K. Nutrient-resorption efficiency of P was higher in Aspurz, of Mg higher in Garde, and there were no differences between sites in N and K. Nutrient-resorption proficiency was significantly higher in the site with lower soil nutrient availability, i.e., for P, Ca, and Mg in Aspurz, but N in Garde (no differences in K); this may be an indicator of nutrient conservation strategy. Annual nutrient productivity (A) was higher for all nutrients in Aspurz, whereas the mean residence time (MRT) was higher in Garde in all nutrients but P. NUE was significantly higher in Garde for all nutrients but P, which was more efficiently used in Aspurz. In both sites, N, P, and K concentrations were higher in the 2002 cohort, Ca in the 2000 cohort, and maximum Mg was found in the 2001 cohort. Thinning caused a reduction of Mg concentration in the 2001 cohort in Aspurz, an increase of Ca resorption proficiency in Aspurz and Mg resorption at both sites, and reduction of P, K, and Mg nutrient response efficiency (NRE) in Garde. Thinning may have caused an increase of the C:Mg ratio through facilitating the development of more biosynthesis apparatus in a more illuminated canopy, but it seemed not to affect resorption in a significant way. Changes in NRE in Garde after thinning show that forest management can affect how trees use nutrients. Our results indicate that the strategy to optimize NUE is different in each stand. In Aspurz (a Mediterranean ecosystem), pine trees carried out resorption more efficiently, while in Garde (a continental forest), trees used nutrients for longer periods of time and reduced their efficiency in using the available soil nutrients after reduced competition by thinning.

Effects of thinning on nutrient content pools in two Pinus sylvestris forests in the western Pyrenees

Abstract Nutrient content [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)] in needles, branches and stems before (P0, not thinned) and after thinning (P20 and P30, 20% and 30% of basal area removed, respectively) was studied in 37- and 32-year-old Pinus sylvestris L. forests in the western Pyrenees: Garde and Aspurz. Thinning significantly decreased all nutrient pools in P20 and P30 relative to P0 on both sites, but no significant differences were found between P20 and P30 owing to low statistical power. Thinning increased the differences between the two forests for total above-ground content of P and Mg, and for the content of N, P and K in the 1999 needles cohort. The former result was due in part to the higher concentration of P (needles and branches) and Mg (needles) in Garde. Therefore, the importance of needles relative to the other nutrient pools increased for N and P after thinning. This may have resulted from the fact that the removal of dead trees with low needle biomass was greater in Garde than in Aspurz. Based on the percentage of basal area removed, nutrient removal in Garde for P30 was higher than expected, apparently owing to an increase in branch removal relative to P20. These results indicate that effects of thinning on nutrient pools were influenced by differences in stand structure and nutrient tissue concentrations between sites.

Increased complementarity in water-limited environments in Scots pine and European beech mixtures under climate change

Ramon y Cajal contract, Grant/Award Number:RYC‐2011‐08082; Spanish Ministry of Economy and Competitiveness, Grant/AwardNumber: AGL2012‐33465; mobility aid,Grant/Award Number: EEBB‐I‐15‐09220; Spanish Predoctoral Research Grant, Grant/Award Number: BES‐2013‐066705.

Tree‐to‐tree competition in mixed European beech–Scots pine forests has different impacts on growth and water‐use efficiency depending on site conditions

Mixed conifer–hardwood forests can be more productive than pure forests and they are increasingly considered as ecosystems that could provide adaptation strategies in the face of global change. However, the combined effects of tree-to-tree competition, rising atmospheric CO2 concentrations and climate on such mixtures remain poorly characterized and understood. To fill this research gap, we reconstructed 34-year series (1980–2013) of growth (basal area increment, BAI) and intrinsic water-use efficiency (iWUE) of Scots pine (Pinus sylvestris L.)–European beech (Fagus sylvatica L.) mixed stands at two climatically contrasting sites located in the southwestern Pyrenees. We also gathered data on tree-to-tree competition and climate variables in order to test the hypotheses that (1) radial growth will be greater when exposed to inter- than to intraspecific competition, that is, when species complementarity occurs and (2) enhanced iWUE could be linked to improved stem radial growth. Growth of both species was reduced when intraspecific competition increased. Species complementarity was linked to improved growth of Scots pine at the continental site, while competition overrode any complementarity advantage at the drought-prone Mediterranean site. Beech growth did not show any significant response to pine admixture likely due to shade tolerance and the highly competitive nature of this species. Increasing interspecific competition drove recent iWUE changes, which increased in Scots pine but decreased in European beech. The iWUE enhancement did not involve any growth improvement in Scots pine. However, the positive BAI-iWUE relationship found for beech suggests an enhanced beech growth in drought-prone sites due to improved water use. Synthesis. Complementarity may enhance growth in mixed forests. However, water scarcity can constrict light-related complementarity for shade intolerant species (Scots pine) in drought-prone sites. Basal area increment–intrinsic water-use efficiency relationships were negative for Scots pine and positive for European beech. These contrasting behaviours have got implications for coping with the expected increasing drought events in Scots pine–European beech mixtures located near the ecological limit of the two species. Complementarity effects between tree species should be considered to avoid overestimating the degree of future carbon uptake by mixed conifer–broadleaf forests.

Están los bosques mixtos pirenaicos de pino silvestre y haya en el camino hacia la saturación por nitrógeno

Rocío Alonso Miguel Álvarez Cobelas Jose Manuel Álvarez-Martínez Mariano Amoroso Enrique Andivia Gabriel Arellano Cristina Armas María Arróniz Crespo Anna Avila Isabel Banos-González Eulogio Bedmar Raquel Benavides Marta Benito Garzón Juan A. Blanco Francisco Javier Bonet García Raphael Boulay Santiago Fernando Burneo Francisco Cabezas Rafael Calama Silvia Calvo Aranda Julio A. Camargo Daisy Cárate-Tandalla José A. Carreira de la Fuente Myriam Catalá Miquel De Cáceres Pilar de la Rua Thibaut Dominique Delsinne Dennis Denis Lucía DeSoto Suárez María T. Domínguez David A. Donoso David A Donoso Jorge Durán María José Endara Blanca Figueroa-Rangel Rubén G. Mateo José M. García del Barrio Enrique García de la Riva Ana I. García-Cervigón Morales Héctor García-Gómez Óscar Godoy Uriel Hernandez Gomez Lorena Gémez Aparicio Penélope González José González Novoa Manuela González Suárez Daniel Griffith Roberto José Guerrero David Gutiérrez Xavier Haro Carrión Laura Hernández Mateo Javier Herrero Asier Herrero Méndez Sheila Izquieta Rojano Luis Lassaletta John Lattke Alex Leverkus Francisco Lloret Jorge Lozano Yudi Lozano Manuel Macía Jaime Madrigal González Esteban Manrique Santiago Martín Alcón Pilar Martín Isabel Javier Martínez Abaigar Jesús Martínez Fernández José Luis Martínez Menéndez Isabel Martínez Moreno Francisco Javier Martínez Vega Marcos Méndez Iglesias Rubén Milla Marcos Miñarro Daniel Moya Navarro Sven Mutke Rafael Ma Navarro Cerrillo Francisco Bruno Navarro Reyes Susana Ochoa Gaona Raúl Ochoa Hueso Daniel Paredes Mauricio Parra Quijano Sergio Pérez Guerrero Carolina Puerta Piñero Neptalí Ramírez-Marcial José V. Roces Díaz Alexandra Rodríguez Carlos Rodríguez Osorio Itziar Rodríguez Urbieta Susana Rodríguez-Echeverría Pere Rovira Paloma Ruiz-Benito Asunción Saldaña Ángela Sánchez-Miranda Fábio Suzart de Albuquerque María Fernanda Tapia-Armijos Jerónimo Torres-Porras María Triviño Raúl Vaca Alejandro Valdecantos Jordi Vayreda Alejandro Velázquez Martínez Albert Vila-Cabrera Rafael Villar Francisco Javier Zamora Camacho Carlos Zamorano-Elgueta Galo Zapata Ríos Lista de revisores que han completado revisiones en el año 2016Visconti, F., de Paz, J.M. 2017. Estimation of the potential CO 2 sequestration and emission capacity of the agricultural soils of the Valencian Community. Ecosistemas 26(1): 91-100. Doi.: 10.7818/ECOS.2017.26-1.15 Agricultural soils have capacity to sequester CO 2 in the form of organic matter. However, this capacity has hardly been quantified and mapped for large territories and with a wide variety of crops, such as the Valencian Community. This task is required to properly size the role of agriculture in any strategy to mitigate climate change. In this paper a first estimate of the potential CO 2 sequestration and emission capacity of the agricultural soils of the Valencian Community down to 20 cm depth has been made. This estimate has been carried out based on the average and spatial variability of the agricultural soil organic matter content in homogeneous agro-ecological zones in climate, soil class and land use, and using GIS, geostatistics and map algebra techniques. The sequestration and emission capacities were found to be 24.0 and 22.0 Mt of carbon, respectively. These values are equivalent to roughly ± 8 years of carbon emissions by use of fossil fuels in the Community itself. This sequestering capacity, which could be reached in 15 to 100 years with the global adoption of management practices that foster soil organic matter accumulation, has an important but insufficient effect compared to the current emission rate. In any case, increasing carbon sequestration in soils, either through management improvement or through organic matter incorporation programs, is very important both to improve sequestration capacity and even more to adapt agroecosystems to climate change.