Ibone Amezaga

Chelate-Enhanced Phytoremediation of Soils Polluted with Heavy Metals

In general, hyperaccumulators are low biomass, slow-growing plants. High biomass non-hyperaccumulator plants by themselves are not a valid alternative for phytoextraction as they also have many limitations, such as small root uptake and little root-to-shoot translocation. In this context, chemically-induced phytoextraction (based on the fact that the application of certain chemicals, mostly chelating agents, to the soil significantly enhances metal accumulation by plants) has been proposed as an alternative for the cleaning up of metal polluted soils. But chelate-induced phytoextraction increases the risk of adverse environmental effects due to metal mobilization during extended periods of time. In order to minimize the phytotoxicity and environmental problems associated with the use of chelating agents, nowadays, research is being carried out on the gradual application of small doses of the chelating agent during the growth period. However, EDTA utilization in the future will most likely be limited to ex situconditions where control of the leachates can be achieved. There are other mobilizing agents which are much less harmful to the environment such as citric acid, NTA, and particularly EDDS. Research should also be aimed towards more innovative agronomic practices. Environmentally safe methods of chelate-induced phytoextraction must be developed before steps towards further development and commercialization of this remediation technology are taken. Most importantly, more applied projects in this field are needed to clarify the real potential and risks of this technology.

Soil enzyme activities as biological indicators of soil health.

Soil health can be defined as the continued capacity of a specific kind of soil to function as a vital living system, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, to maintain or enhance the quality of air and water environments, and to support human health and habitation. Because of the conflicting pressures increasingly applied to the soil, it is clear that relevant indicators are urgently needed to assess and monitor soil health. Biological indicators of soil health offer certain advantages over physicochemical methods. Among the various biological indicators that have been proposed to monitor soil health, soil enzyme activities have great potential to provide a unique integrative biological assessment of soils and the possibility of assessing the health of the soil biota. Besides, soil enzyme activities provide an easy, relatively rapid, and low cost procedure to monitor soil health. Nevertheless, soil enzyme activities also present some limitations and must always be considered in conjunction with other biological and physicochemicals measurements if we are to diagnose soil health correctly.

Resource partitioning of four sympatric bark beetles depending on swarming dates and tree species

Abstract The niche relationships among bark beetle species attacking pines in northern Spain were studied at three localities with respect to tree species (Pinus radiata and P. sylvestris) and swarming time. Four bark beetle species were found attacking the trees, but not all four species were present at all sites: Tomicus piniperda, Ips sexdentatus, Orthotomicus erosus and Pityogenes bidentatus. Niche width and overlap were affected by resource availability, arrival sequence and attack density. In general, T. piniperda showed the widest niche breadth and was the first swarming species. The largest niche overlaps were found at the sites where the resource was less limiting. The niche overlap between T. piniperda and O. erosus depended mainly on the swarming time. The portion of the niche of O. erosus occupied by T. piniperda was greater than that of T. piniperda occupied by O. erosus at the site in which T. piniperda swarmed first. In general, the bark species appeared segregated from each other, bark thickness being a good segregating factor.

Grazing Intensity, Aspect, and Slope Effects on Limestone Grassland Structure

Abstract Three treatments were used to evaluate the effect of grazing intensity (ca 30% and 50% herbage removal), aspect (north and south), and slope (< 10% and 10%–30%) on plant community structure of mountain grasslands in the Basque Country (Spain). Plant species richness was not significantly affected by grazing intensity, aspect, or slope. Although plant species composition was similar (Sorensens similarity index = 0.87) between both grazing intensities, species frequency and cover were affected by grazing intensity. Festuca rubra L. and Agrostis capillaris L. were the most common species under both grazing pressures. Moderate grazing intensity (50% herbage removal) plots contained a greater number of plant species with a frequency of more than 50%. The lowest cover for F. rubra corresponded to low grazing intensity, north aspects, and steeper slopes. The lowest cover for A. capillaris was found under low grazing intensity (30% herbage removal) and steeper slopes. Danthonia decumbens (L.) P. C., Potentilla erecta (L.) Räuschal, and Trifolium repens L. were significantly affected by aspect and grazing intensity. Low grazing intensity on sites with northern aspects and steep slopes favored Agrostis curtisii Kerguélen, a species with a low nutritional value. A. capillaris, A. curtisii, P. erecta, and T. repens were sensitive to soil properties and aspect. Nitrogen and K soil concentrations were significantly higher in areas with low grazing intensity, most likely due to greater dead herbage accumulation. Significant (P < 0.05) correlations between plant species and soil pH or P concentration were found in areas with low grazing intensity. Reduction in grazing intensity together with the effect of slope and northern aspect has resulted in changes in plant community structure, leading to increases in forages with lower nutritional value.

Bioluminescent bacterial biosensors for the assessment of metal toxicity and bioavailability in soils.

A major factor governing the toxicity of heavy metals in soils is their bioavailability. Traditionally, sequential extraction procedures using different extractants followed by chemical analysis have been used for determining the biologically available fraction of metals in soils. Yet, the transfer of results obtained on non-biological systems to biological ones is certainly questionable. Therefore, bioluminescence-based bacterial biosensors have been developed using genetically engineered microorganisms, constructed by fusing transcriptionally active components of metal resistance mechanisms to lux genes from naturally bioluminescent bacteria like Vibrio fischeri for the assessment of metal toxicity and bioavailability in polluted soils. As compared to chemical methods, bacterial biosensors present certain advantages, such as selectivity, sensitivity, simplicity, and low cost. Despite certain inherent limitations, bacterial bioluminescent systems have proven their usefulness in soils under laboratory and field conditions. Finally, green fluorescent protein-based bacterial biosensors are also applicable for determining with high sensitivity the bioavailability of heavy metals in soil samples.

Effect of Intraspecific Competition on Progeny Production of Tomicus piniperda (Coleoptera: Scolytidae)

Abstract Intraspecific competition in Tomicus piniperda (L.) was studied in Ascot, United Kingdom, with special emphasis on its effect on progeny adult (i.e., offspring) weight and progeny production. Although the weight of female progeny adults was significantly decreased by increasing attack density (density of colonization), the latter did not significantly affect weight of male progeny adults. Similarly, increasing adult female weight was significantly related to increasing egg gallery length, number of hatched eggs, and final production of progeny adults. This production was also affected by host (tree) species. Females breeding in Pinus sylvestris (L.) showed a higher production of progeny adults than those in Pinus nigra variety maritima (Ait.) Melville. Overall, increasing intraspecific competition appears to contribute to the regulation of T. piniperda populations through reduction of weight and fecundity of female progeny.

Efficacy of Management Policies on Protection and Recovery of Natural Ecosystems in the Urdaibai Biosphere Reserve

ABSTRACT: Knowledge of landscape patterns and dynamics is essential for land use planners and natural resources managers. They need to know how landscapes have changed in order to determine the consequences and efficacy of the management policies and implement future decision-making. This study characterized the landscape of the Urdaibai Biosphere Reserve, which has been affected by the introduction of exotic tree species since the beginning of the 20th century. We examined the dynamics of this landscape between 1991 and 2009 and the consequences of having been declared a UNESCO Biosphere Reserve in 1984. Most of the Urdaibai Biosphere Reserve potential vegetation (80%) is mixed-oak (Quercus robur L.) forest, but, currently, this forest is found in only 6.5% of the area. Most of the current vegetation (54%) comprises Pinus radiata and Eucalyptus sp. plantations. Over the period studied, land use had changed in only 11.8% of the area. Nearly 30% of the change was the replacement of traditional grasslands, crops, and heathlands by P. radiata and Eucalyptus sp. plantations. However, 22% of the change had reflected a recovery of the native vegetation, namely mixed-oak and Cantabrian evergreen-oak (Quercus ilex subsp. Ilex) forest, coastal sandy areas, or broad-leaf plantations. This recovery of the native vegetation has countered the tendency towards landscape degradation observed since 1957. Thus, despite the small change described, the first effects of conservation and environmental recovery policies can be detected. Nevertheless, there remains much to be done for recovering the natural ecosystem; the most difficult obstacles include the fact that most of the land is privately owned and an existence of the administrative complexity gives rise to problems that exist between different Administrations.

At which spatial scale are plant species composition and diversity affected in beech forests

Abstract• ContextLandscape structure is crucial for forest conservation in regions where the natural forest is fragmented. Practical conservation is currently shifting from local stands to a landscape perspective, although few studies have tested the relative effects of different spatial scales on plant species composition and diversity in forests.• MethodsWe studied vascular plants and 17 predictor variables related to landscape (i.e. patch size or the surrounding landscape matrix) and stand conditions (i.e. soil pH and stand structure) in 50 semi-natural beech (Fagus sylvatica L.) forests in the northern Iberian Peninsula.• AimsWe analysed the effect of landscape heterogeneity and stand-associated environmental conditions on plant species composition and diversity. Moreover, we studied the influence of these scales on the diversity of different life forms.• ResultsPlant species composition and diversity responded primarily to suitable habitat proportions in the surrounding landscape and secondarily to soil pH. The response to these factors differed among life forms. Species diversity, especially tree and shrub diversity, increased with increases in the proportion of ecologically similar habitat in the surrounding landscape (forests dominated by Quercus spp.). Species diversity (primarily herb diversity) also increased with increasing soil pH.• ConclusionFuture landscape management should seek to produce a heterogeneous matrix comprising patches of natural, unmanaged and managed deciduous forest and including other traditional uses and forest plantations.

Climbing a Ladder: A Step-by-Step Approach to Understanding the Concept of Agroecosystem Health

Population and individual health is linked to agroecosystem health. To comprehend the concept of agroecosystem health, one should climb a ladder consisting of several successive steps, each rung presenting a certain degree of instability (conceptual difficulty and uncertainty) in an advisable but not inevitable order. Here we suggest a ladder consisting of the following concepts: ecosystem, agroecosystem, biodiversity, sustainability, ecosystem health, and agroecosystem health. Although these concepts are to a certain extent well understood and grasped by scientists, politicians, natural resource managers, and environmentalists, some steps are still highly debatable, unclear, and present a considerable degree of reluctance to be defined and understood. Consequently, much empirical and theoretical effort must be made to construct solid conceptual ladders made up of such steps. In this enterprise, a traditional reductionistic approach confining interpretations to narrow scientific disciplines is unadvisable. Holistic, transdisciplinary approaches are required to reach the desired goal.