José R. Quintana

Fire activity projections in the SRES A2 and B2 climatic scenarios in peninsular Spain

Climate change is affecting the meteorological and climatic conditions in which forest vegetation develops. These conditions are also determinant in present and future forest fire activity. In order to quantify the expected alterations in future fire activity, we built linear regression models using monthly meteorological variables and the recorded fire activity in peninsular Spain. These models were developed for 15 territories and for the number of fires, the forest area burned and the wooded forest area burned. The meteorological variables used as predictors are derived from a Regional Climate Model covering the period 1961–90 as the control scenario and 2071–2100 as the future scenario. In the 13 territories with valid models, the explained variance ranged from 20 to 68% for the number of fires, from 12 to 66% for the forest area burned, and from 12 to 62% for the wooded forest area burned. Based on these models, we calculated the ratios between the estimations for the climatic scenarios SRES A2 and B2 and the estimates for the control period. For the entire area and for the A2/control and B2/control respectively, the ratios are 2.5 and 2 times for the number of fires, 4.6 and 3.4 for the forest area burned and 3.9 and 3 times for the wooded forest area burned. In spite of the uncertainties regarding future climatic scenarios as well as the simplicity of the model, the results nevertheless point to a very significant increase in fire activity. Forest management should therefore be focussed on adaptation procedures as well as on ecosystem resilience. This strategy will promote a more sustainable coexistence of forests and fires in altered fire regimes.

Improving the relationship between soil characteristics and metal bioavailability by using reactive fractions of soil parameters in calcareous soils

The contribution of the nature instead of the total content of soil parameters relevant to metal bioavailability in lettuce was tested using a series of low-polluted Mediterranean agricultural calcareous soils offering natural gradients in the content and composition of carbonate, organic, and oxide fractions. Two datasets were compared by canonical ordination based on redundancy analysis: total concentrations (TC dataset) of main soil parameters (constituents, phases, or elements) involved in metal retention and bioavailability; and chemically defined reactive fractions of these parameters (RF dataset). The metal bioavailability patterns were satisfactorily explained only when the RF dataset was used, and the results showed that the proportion of crystalline Fe oxides, dissolved organic C, diethylene-triamine-pentaacetic acid (DTPA)-extractable Cu and Zn, and a labile organic pool accounted for 76% of the variance. In addition, 2 multipollution scenarios by metal spiking were tested that showed better relationships with the RF dataset than with the TC dataset (up to 17% more) and new reactive fractions involved. For Mediterranean calcareous soils, the use of reactive pools of soil parameters rather than their total contents improved the relationships between soil constituents and metal bioavailability. Such pool determinations should be systematically included in studies dealing with bioavailability or risk assessment.

Towards Integrated Understanding of the Rhizosphere Phenomenon as Ecological Driver: Can Rhizoculture Improve Agricultural and Forestry Systems?

Agriculture and forestry traditionally focus on improving plant growth traits based on an anthropocentric point of view. This paradigm has led to global problems associated to soil overexploitation such as soil losses, reductions of the C stock in soils, and the generalized use of fertilizers, which particularly increases the costs of production and pollution treatment. This view may also have limited our understanding of mutualistic symbioses of plants and microorganisms assuming that the main role of non-photosynthetic symbionts is to mobilize the nutrients that are necessary for plant growth and development, and being plants the dominant agents of the symbiotic relationship. In response to these issues, this chapter offers an alternative approach taking advantage of the “rhizo-centric” point of view, where non-photosynthetic partners are the main protagonists in play; and secondly, it builds a multidisciplinary body of knowledge that could be called “rhizoculture”, which includes techniques focussing on the intensification of the development and activity of roots, mycorrhizae, and other symbiotic and free living rhizosphere organisms. In short, rhizoculture may lead to decrease plant production dependence on fertilization and provides other benefits to agriculture, forestry, and the environment. Within this conceptual framework, the first objective of this book chapter is to explore whether there is a “paradox of calcium salts” (i.e., Ca2+ and its salts are simultaneously nutrients, promoters, and stressors for the host plants) that would explain a dominance of mycorrhizal fungi over plants based on inducing a Ca(pH)–mediated chlorosis to the host plants. If this paradigm shifting hypothesis were finally fully verified, it would provide conceptual bases to reconsider our current technologies in agriculture and forestry by introducing the “rhizocultural” approach, based on the management of roots (introducing alternative cultural practices), Ca2+ salts (using liming and other techniques), rock-eating mycorrhizae, organic matter, and the soil microbiome (increasing the presence of symbiotic microorganisms against saprophytes), N and P contents (by aquaculture and smart recycling of organic waste), and the physical properties of the soil (by the activity of soil symbiotic microorganisms and soil fauna, such as ants, termites and earthworms). The development of such new technological approaches in rhizoculture would significantly decrease the high cost and associated pollution of the application of fertilizers and phytochemicals; as well as it would increase soil C stocks, improve the resilience of agricultural and forest systems to environmental disturbances, such as climate change, and enhance food production and security.