Cristina Lull

Environmentally induced changes in antioxidant phenolic compounds levels in wild plants

Different adverse environmental conditions cause oxidative stress in plants by generation of reactive oxygen species (ROS). Accordingly, a general response to abiotic stress is the activation of enzymatic and non-enzymatic antioxidant systems. Many phenolic compounds, especially flavonoids, are known antioxidants and efficient ROS scavengers in vitro, but their exact role in plant stress responses in nature is still under debate. The aim of our work is to investigate this role by correlating the degree of environmental stress with phenolic and flavonoid levels in stress-tolerant plants. Total phenolic and antioxidant flavonoid contents were determined in 19 wild species. Meteorological data and plant and soil samples were collected in three successive seasons from four Mediterranean ecosystems: salt marsh, dune, semiarid and gypsum habitats. Changes in phenolic and flavonoid levels were correlated with the environmental conditions of the plants and were found to depend on both the taxonomy and ecology of the investigated species. Despite species-specific differences, principal component analyses of the results established a positive correlation between plant phenolics and several environmental parameters, such as altitude, and those related to water stress: temperature, evapotranspiration, and soil water deficit. The correlation with salt stress was, however, very weak. The joint analysis of all the species showed the lowest phenolic and flavonoid levels in the halophytes from the salt marsh. This finding supports previous data indicating that the halophytes analysed here do not undergo oxidative stress in their natural habitat and therefore do not need to activate antioxidant systems as a defence against salinity.

Isolation, structural assignment and insecticidal activity of (−)-(1S,2R,3R,4S)-1,2-epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetate, a natural product from Minthostachys tomentosa

Abstract (−)-(1 S ,2 R ,3 R ,4 S )-1,2-Epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetate has previously been identified as the active compound of Minthostachys tomentosa responsible for the insecticidal activity against Oncopeltus fasciatus . Its structure was initially assigned on the basis of spectral data. In order to confirm the structure and to define the stereochemistry, stereoselective synthesis of its enantiomer, (+)-(1 R ,2 S ,3 S ,4 R )-1,2-epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetate, starting from ( R )-(−)-piperitone, was carried out using a Sharpless reaction as the key step. The natural product is dextro -rotatory while the synthetic product is levo -rotatory. Measurements of insecticidal activities of the different steroisomers revealed that only the natural product is active.

Ecohydrological-Based Forest Management in Semi-arid Climate

The role of forests on the provision and regulation of non-marketed ecosystem services is well known (Thorsen et al. 2014). This is especially important in areas like the Mediterranean, where protective forests play a major role against soil erosion and degradation, landscape quality and stabilization of the hydrological cycle. Socio-economic and cultural changes affecting rural society from the 1960s have produced a demographic decline, and with it, an abandonment of rural activities, leading to an expansion and densification of forest and scrub. Forest encroachment may decrease the streamflow from upper catchments (Gallart and Llorens 2004); this study reports a decrease in average annual flow of major Spanish rivers between 37 and 59%, partly explained by the densification of upstream forests, and increasing interception loss. Moreover, some Mediterranean basins (e.g. Segura and Jucar in Spain) present very serious problems of water scarcity, because of a combination of low/irregular rainfall and high rates of evapotranspiration, that has resulted in overuse of groundwater resources (Estrela et al. 2000a, b). These problems may even endanger urban water supply (approx. 15% of the total water supply in Spain). In addition, the Mediterranean region is already suffering some significant impacts of the climate change, such as longer dry seasons, or lower soil moisture content (Giorgi and Lionello 2008; Garcia-Ruiz et al. 2011). All these issues have raised concern about the importance of forests and water interactions in the Mediterranean (Birot et al. 2011).

Hydrology-oriented forest management trade-offs. A modeling framework coupling field data, simulation results and Bayesian Networks

Hydrology-oriented forest management sets water as key factor of the forest management for adaptation due to water is the most limiting factor in the Mediterranean forest ecosystems. The aim of this study was to apply Bayesian Network modeling to assess potential indirect effects and trade-offs when hydrology-oriented forest management is applied to a real Mediterranean forest ecosystem. Water, carbon and nitrogen cycles, and forest fire risk were included in the modeling framework. Field data from experimental plots were employed to calibrate and validate the mechanistic Biome-BGCMuSo model that simulates the storage and flux of water, carbon, and nitrogen between the ecosystem and the atmosphere. Many other 50-year long scenarios with different conditions to the ones measured in the field experiment were simulated and the outcomes employed to build the Bayesian Network in a linked chain of models. Hydrology-oriented forest management was very positive insofar as more water was made available to the stand because of an interception reduction. This resource was made available to the stand, which increased the evapotranspiration and its components, the soil water content and a slightly increase of deep percolation. Conversely, Stemflow was drastically reduced. No effect was observed on Runof due to the thinning treatment. The soil organic carbon content was also increased which in turn caused a greater respiration. The long-term effect of the thinning treatment on the LAI was very positive. This was undoubtedly due to the increased vigor generated by the greater availability of water and nutrients for the stand and the reduction of competence between trees. This greater activity resulted in an increase in GPP and vegetation carbon, and therefore, we would expect a higher carbon sequestration. It is worth emphasizing that this extra amount of water and nutrients was taken up by the stand and did not entail any loss of nutrients.