Sensitivity to nitrate and nitrite in pond-breeding amphibians from the Pacific northwest, USA

In static experiments, we studied the effects of nitrate and nitrite solutions on newly hatched larvae of five species of amphibians, namely Rana pretiosa, Rana aurora, Bufo boreas, Hyla regilla, and Ambystoma gracile. When nitrate or nitrite ions were added to the water, some larvae of some species reduced feeding activity, swam less vigorously, showed disequilibrium and paralysis, suffered abnormalities and edemas, and eventually died. The observed effects increased with both concentration and time, and there were significant differences in sensitivity among species. Ambrystoma gracile displayed the highest acute effect in water with nitrate and nitrite. The three ranid species had acute effects in water with nitrite. In chronic exposures, R. pretiosa was the most sensitive species to nitrates and nitrites. All species showed 15-d LC50s lower than 2 mg N-NO2 /L. For both N ions, B. boreas was the least sensitive amphibian. All species showed a high mortality at the U.S. Environmental Protection Agency- recommended limits of nitrite for warm-water fishes (5 mg N-NO2 /L) and a significant larval mortality at the recommended limits of nitrite concentration for drinking water (1 mg N-NO2 The recommended levels of nitrate for warm-water fishes (90 mg N- NO3 /L) were highly toxic for R. pretiosa and A. gracile larvaePeer reviewe

Diseño y fabricación 3D de componentes para reactores de despolimerización de lignina: Batch y continuo

La lignina es uno de los tres componentes poliméricos principales de la biomasa junto a la celulosa y hemicelulosa. Está presente en materias de origen vegetal como la madera, por lo que altas cantidades de lignina se generan como residuo en tratamientos de obtención celulosa (proceso común en industrias papeleras). Aunque parte de la lignina se aprovecha energéticamente en las propias plantas papeleras, esta se ha convertido en un producto atractivo por constituir una fuente potencial de precursores de alto valor añadido, de la que se pueden obtener compuestos aromáticos de bajo peso molecular a partir de su despolimerización. En este trabajo se ha realizado el diseño de dos tipos de reactores de despolimerización de lignina, uno para el proceso en continuo y el segundo en batch. Dichos prototipos se fabricarán haciendo uso de técnicas de impresión 3D y se probarán para comprobar que el diseño sea funcional. Uno de los principales retos en el proceso de despolimerización es la recuperación del catalizador que se haya mezclado con los restos de madera iniciales, por lo que este trabajo fin de grado se centra en el diseño de sistemas de reacción (tanto en continuo como en discontinuo) que permitan una buena recuperación y/o separación del catalizador.Lignin is one of the three main polymeric components of biomass together with cellulose and hemicellulose. It’s found in vegetable materials such as wood, so high amounts of lignin are generated as waste in cellulose obtaining treatments (a common process in the paper industry). Although part of the lignin is processed in the paper mills themselves, it has become an attractive product because it constitutes a potential source of high added value precursors, from which aromatic compounds of low molecular weight can be obtained from its depolymerization. In this work, the design of two types of lignin depolymerization reactors has been carried out, one for the continuous process and the second one in batch. These prototypes will be manufactured using 3D printing techniques and tested to verify that the design is functional. One of the main challenges in the depolymerization process is the recovery of the catalyst that has been mixed with the initial wood residues, so this final degree work focuses on the design of reaction systems (both continuous and batch) that allow a good recovery and/or separation of the catalyst.Graduado o Graduada en Ingeniería Mecánica por la Universidad Pública de NavarraIngeniaritza Mekanikoko Graduatua Nafarroako Unibertsitate Publikoa

Large-scale assessment of regeneration and diversity in Mediterranean planted pine forests along ecological gradients

15 pages, 4 figures, 4 tables, 87 references.There is increasing concern regarding sustainable management and restoration of planted forests, particularly in the Mediterranean Basin where pine species have been widely used. The aim of this study was to analyse the environmental and structural characteristics of Mediterranean planted pine forests in relation to natural pine forests. Specifically, we assessed recruitment and woody species richness along climatic, structural and perturbation gradients to aid in developing restoration guidelines.Location Continental Spain. We conducted a multivariate comparison of ecological characteristics in planted and natural stands of main Iberian native pine species (Pinus halepensis, Pinus pinea, Pinus pinaster, Pinus nigra and Pinus sylvestris). We fitted species-specific statistical models of recruitment and woody species richness and analysed the response of natural and planted stands along ecological gradients. Planted pine forests occurred on average on poorer soils and experienced higher anthropic disturbance rates (fire frequency and anthropic mortality) than natural pine forests. Planted pine forests had lower regeneration and diversity levels than natural pine forests, and these differences were more pronounced in mountain pine stands. The largest differences in recruitment – chiefly oak seedling abundance – and species richness between planted and natural stands occurred at low-medium values of annual precipitation, stand tree density, distance to Quercus forests and fire frequency, whereas differences usually disappeared in the upper part of the gradients.Main conclusions Structural characteristics and patterns of recruitment and species richness differ in pine planted forests compared to natural pine ecosystems in the Mediterranean, especially for mountain pines. However, management options exist that would reduce differences between these forest types, where restoration towards more natural conditions is feasible. To increase recruitment and diversity, vertical and horizontal heterogeneity could be promoted by thinning in high-density and homogeneous stands, while enrichment planting would be desirable in mesic and medium-density planted forests.This research was supported by INTERBOS3-CGL2008-04503- C03-03 (MCI) and SUM2008-00004-C03-01 (INIA) projects. P.R.B. was supported by a FPU fellowship from the Spanish MEC (AP2008-01325). We thank the MARM (Ministerio de Medio Ambiente, Medio Rural y Marino, Dirección General de Medio Natural y Política Forestal) for granting the access to the Spanish Forest Inventory Data.Peer reviewe

Conservation of Mediterranean oak woodlands: understorey dynamics under different shrub management

The effect of experimental disturbances on the dynamics of a shrub community was studied on a ‘Montado’ ecosystem, in southern Portugal. The evolution of the community physiognomy, composition and diversity were monitored after shrub clearing followed by biomass removal, deposition on soil surface and incorporation with the soil, over a 9-year period. Maximum shrub density was recorded in the first year after the disturbances, excepting in mulched plots which showed the greatest number of individuals 1 year later. The increment of shrub leaf biomass was very fast in the first 3 years, whereas wood production was slower but occurred along the whole study period. At the end of the study, leaf and wood biomass was still significantly lower than in the predisturbance situation. The variation pattern of leaf area index was similar to that of leaf biomass. The evolution of total plant cover and diversity was similar across treatments. The highest species richness and diversity were recorded 2 years after cutting, decreasing afterwards with the increasing dominance of shrubs. Thus it seems likely that, although a 9 year period is too short for these communities to reach steady equilibrium, they are very resistant and resilient to disturbances, as regeneration was fast and vegetation dynamics was not influenced by differences among treatments. We can conclude that shrub clearing promotes biodiversity and the time of permanence of shrub patches depends on the particular goal we want to achieve

Conservation of Mediterranean oak woodlands: understorey dynamics under different shrub management

The effect of experimental disturbances on the dynamics of a shrub community was studied on a ‘Montado’ ecosystem, in southern Portugal. The evolution of the community physiognomy, composition and diversity were monitored after shrub clearing followed by biomass removal, deposition on soil surface and incorporation with the soil, over a 9-year period. Maximum shrub density was recorded in the first year after the disturbances, excepting in mulched plots which showed the greatest number of individuals 1 year later. The increment of shrub leaf biomass was very fast in the first 3 years, whereas wood production was slower but occurred along the whole study period. At the end of the study, leaf and wood biomass was still significantly lower than in the predisturbance situation. The variation pattern of leaf area index was similar to that of leaf biomass. The evolution of total plant cover and diversity was similar across treatments. The highest species richness and diversity were recorded 2 years after cutting, decreasing afterwards with the increasing dominance of shrubs. Thus it seems likely that, although a 9 year period is too short for these communities to reach steady equilibrium, they are very resistant and resilient to disturbances, as regeneration was fast and vegetation dynamics was not influenced by differences among treatments. We can conclude that shrub clearing promotes biodiversity and the time of permanence of shrub patches depends on the particular goal we want to achieve

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Abstract The dehydrogenase activity (DHA) in the upper 10 cm of forest soils was measured in three experimental plots (1 ha) in Los Alcornocales Natural Park (southern Spain). In each plot, a sylviculture treatment of thinning and shrub-clearing had been previously carried out in one half, while the other half was left as a forest control. Soil samples were taken during the dry season (July 2000) and after the first autumn rains (October 2000). The DHA of forest soil in autumn [527±165 nmol p-iodonitrotetrazolium formazan (INTF) g -1 h -1 ] was almost double that in summer (289±95 nmol INTF g -1 h -1 ), for one of the studied plots. During the dry season, DHA of forest control soils (324±85 nmol INTF g -1 h -1 ) was higher than in the thinned and shrub-cleared forest (253±93 nmol INTF g -1 h -1 ). During the autumn (wet season), however, the effects of the sylvicultural practices on the soil dehydrogenase were negligible. Significant differences in DHA were found between the three sites. Multiple regression analysis identified pH as the best predictor of DHA of these soils. Other soil properties (pH, K, Ca, Mg, and soil moisture) also showed significant correlations with DHA. In addition, clay content appeared to enhance the enzyme activity. Our results suggest that thinning and shrub-clearing in Mediterranean forests seem to affect negatively the soil DHA, and their impact is more marked during the dry season. However, season and site effects are better determinants of DHA than management practices