English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

Desertification refers to the degradation of land [1–4]. As a severe global environmental problem, it has drawn considerable attention from the international community. The United Nations Convention to Combat Desertification [4] was adopted by the United Nations in 1994, and since that time, countries around the world have made ever-increasing efforts to combat desertification [5–12]. However, the spread of desertification has not been controlled. Instead, it is becoming even worse; it is expanding at a rate of 50 000–70 000 km annually [13,14]. At present, desert and other dryland regions endangered by global desertification account for 41.3% of Earth’s land area [2,15–17]. In China, the desertified land is approximately 1.73 × 10 km which is 18.03% of the national territory, and another 3.1 × 10 km is tending to be desertified [18]. Desert control poses a global challenge. Presently, there exist three prevailing types of methods of desert control [1,9–12,19]: engineering methods, chemical methods, and vegetation methods. These methods have all played a positive role in desert control. The principle of engineering methods is to prevent the drifting of sand by building barriers, such as straw checkerboard barriers and sand fences. Chemical methods involve spraying oil, bitumen or latex onto the surface of sand to cause the surface layer to solidify. In vegetation methods, sand is usually remediated through the planting of psammophytes. However, none of the above methods is capable of changing the material characteristics of sand into those of soil. The proposition of desert “soilization” is based on the realization of sand “soilization,” which presents a promising alternative to the prevailing methods of desert control. Sand “soilization,” i.e., the turning of sand into “soil,” is a remarkable transformation based on the revelation of the eco-mechanical attributes of soil. It has been found by Yi et al. [20] that the mechanical properties and ecological attributes of soil are closely correlated. Soil is in a rheological state when wet and in a solid state when dry, and it can readily transform between these two states. These mechanical properties of soil endow it with the two eco-mechanical attributes of self-repair and self-regulation. An analysis by Yi et al. [20] has shown that these two attributes are the prerequisites for soil to maintain its endless eco-cycle and to serve as an ideal habitat for plants. If these two attributes are lost, then the soil will degrade, and one of two scenarios may emerge: soil hardening or soil desertification. Based on the above finding, sand “soilization” has been achieved by Yi et al. by imposing an appropriate constraint among the sand granules. Sand, as it is defined in geology or engineering [19,21], exists in a discrete state, and the constraint that acts among its granules is a contact constraint. When a suitable water-based paste is added to and mixed with sand granules, then an omni-directional integrative (ODI) constraint (with omni-directionality and restorability) will form among the granules instead, and the sand will be transformed into a rheological state (wet “soil”) [20]. After the evaporation of the water content in the paste, the ODI constraint will transition into a fixed constraint, and the sand will transform into a solid state (dry “soil”). “Soilized” sand possesses the mechanical properties of natural soil, which can continuously transform between the rheological state and the solid state. Thus, such “soilized” sand possesses the same eco-mechanical attributes as those of soil. Because the necessary constraint is imposed on the sand granules by means of a water-soluble paste, this “soilized” sand also possesses a strong capacity to retain water, nutrients, and air. Clearly, there is no significant difference between the “soilized” sand and natural soil in terms of their mechanical properties and ecological attributes. Yi [22] has found that once sand is “soilized,” it becomes suitable for the growth of plants, thus making it an ideal habitat for plants. Since 2013, we have been conducting an outdoor planting experiment at two sites (with areas of approximately 550 m and 420 m, respectively) in the Nan’an District of Chongqing, China. Desert landform conditions were simulated in the experiment by establishing a 15-cmto 25-cm-thick plain sand layer underlain by a 20-cmto 30-cm-thick gravel layer on the ground. Afterward, three types of “soilized” sand layers with thicknesses of 10–20 cm, which were obtained by mixing sand with a modified sodium carboxymethyl cellulose (CMC) solution (containing 2% modified CMC and 5% compound fertilizer) at a weight ratio of 1: 0.15, were placed on top of the plain sand layer in separate sections. Three types of commercially available sand for building and construction (clean river sand), with different fineness moduli of 1.22, 2.97, and 3.71 and without any soil content, were subjected to “soilization” for the experiment. In addition to these river sands, three other granular materials (machine-made sand from stone, sand mixed with machine-made sand from stone, and sand mixed with saw-dust) were also used in the planting experiment after “soilization.” Many types of plants (Fig. 1(a)), such as rice (Fig. 1(b)), corn (Fig. 1(c)), and sweet potatoes (Fig. 1(d)), were planted in the “soilized” sand. In each year of the experiment, the

Desert “Soilization”: An Eco-Mechanical Solution to Desertification