Oinez Basoa: Using school-managed afforested land for soil education in Navarre, Spain

The study of soils in secondary education is a topic of debate because it remains little considered in official curricula and programs at pre-university education, despite the increasing concern about soil in environmental studies. In this work, we present the results of a case-study conducted with a class of the 4th grade of compulsory secondary education (10th school year), where a didactic sequence was used that included actual data obtained in an afforestation chronosequence. The afforestation was part of the activities conducted by the network of schools to which the school belonged, with the aim of mitigating greenhouse gas emissions resulting from their annual fund-raising event. In a first step, a series of indicators related to soil and vegetation were determined in the afforested soil using a space-for-time approach with a nearby cultivated soil (corresponding to the original situation of the afforested soil) and a mature forest (similar to the target situation of the afforested land). Plant biodiversity, soil microbial biomass C and total organic C, and organic matter decomposition indicators were determined and observed to be in an intermediate situation in the afforested land between the cultivated soil and the mature forest, seven years after afforestation. In particular, an effective atmospheric C sequestration was verified from a difference of 12.41 ± 1.06 Mg of organic C per hectare in the afforested soil compared to the cultivated control. Data issued from this analysis were used to prepare a collaborative jigsawactivity that was integrated into the didactic sequence designed to introduce the concepts of ecosystem successions and the carbon cycle. This project had a special focus on the role of soil both as a component of the ecosystem and within the carbon cycle. The success of the implementation of this sequence was tested using an initial and final test. The results of these tests showed a general improvement (42.8 points in the final test vs 23.3 in the initial test) in relation to the concepts tested. However, differences were observed in relation to the progression done by the students, which was better for ecosystems than for soil, likely as a consequence of the poor previous knowledge. From those results, we conclude that the development of educational tools that allow secondary school students to address real cases in which the soil is considered as a key component of the ecosystem can be effective in moving towards meaningful learning about soils and soil properties, since these seem still poorly understood by secondary school students.