Transdisciplinary approaches that provide holistic views are essential to properly understand soil processes and the importance of soil to society and will be crucial in the future to integrate distinct disciplines into soil studies. A myriad of challenges faces soil science at the beginning of the 2020s. The main aim of this overview is to assess past achievements and current challenges regarding soil threats such as erosion and soil contamination related to different United Nations sustainable development goals (SDGs) including (1) sustainable food production, (2) ensure healthy lives and reduce environmental risks (SDG3), (3) ensure water availability (SDG6), and (4) enhanced soil carbon sequestration because of climate change (SDG13). Twenty experts from different disciplines related to soil sciences offer perspectives on important research directions. Special attention must be paid to some concerns such as (1) effective soil conservation strategies; (2) new computational technologies, models, and in situ measurements that will bring new insights to in-soil process at spatiotemporal scales, their relationships, dynamics, and thresholds; (3) impacts of human activities, wildfires, and climate change on soil microorganisms and thereby on biogeochemical cycles and water relationships; (4) microplastics as a new potential pollutant; (5) the development of green technologies for soil rehabilitation; and (6) the reduction of greenhouse gas emissions by simultaneous soil carbon sequestration and reduction in nitrous oxide emission. Manuscripts on topics such as these are particularly welcomed in Air, Soil and Water Research.

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The Mediterranean shrub Cistus ladanifer grows naturally in São Domingos (Portugal), an abandoned copper mine. High levels of trace elements in plants can generate oxidative stress increasing the activity of antioxidant enzymes. The aim of this work was to evaluate and compare As, Cu, Pb and Zn concentrations and the activity of the soluble and cell wall ionically bounded forms of the enzymes catalase, peroxidase and superoxide dismutase in leaves of C. ladanifer, collected in spring and summer, growing on São Domingos mine and on a non-contaminated area (Pomarão). São Domingos soils showed high total concentrations of As (2.6 g kg(-1)) and Pb (7.3 g kg(-1)) however the available fraction represented less than 1.5% of the total. C. ladanifer population from mine showed tolerance to Pb and Zn, which attain in leaves concentrations considered toxic for plants. The enzymatic activity of catalase, peroxidise and superoxide dismutase varied with plant populations and seasons, although with no particular trend, being specific to each trace element and enzyme cell localization. Catalase activity was evenly distributed between the soluble and ionically bounded forms, whereas the ionically bounded form of peroxidase predominated relatively to total activity, and the opposite was observed for superoxide dismutase. Spring and summer leaves from the two areas presented enzymatic activities in both fractions except to peroxidase soluble activities in leaves collected in summer. C. ladanifer enzymatic activity seems to be related with the co-existence of different stress factors (trace elements concentration, temperature, UV radiation and drought). The survival and growth of this species on contaminated mining soils is due to the presence of effective antioxidant enzyme-based defence systems.

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