Classify different types of terrace in agriculture
Answers
Examples of diverse terracing types. (Note: terracing can be classified in different ways 212 due to diversity in practice. Taking China as examples: (a) paddy Lonji bench terraces, (b) paddy 213 terraces in Union County of Fujian, (c) Hani Heritage Terrace Landscape, (d) dryland broad-based 214 terraces in the Loess Plateau for agricultural production, (e) zig terraces for ecosystem restoration 215 with planted arborvitae, (f) sloping terraces in Chongqing: brick-wall construction for vegetation 216 restoration in the upper hillslope and for crops in the lower hillslope)
For thousands of years, humans have created different types of terraces in different sloping conditions, meant to mitigate flood risks, reduce soil erosion and conserve water. These anthropogenic landscapes can be found in tropical and subtropical rainforests, deserts, arid and semiarid mountains across the globe. Despite the long history, the roles of and the mechanisms by which terracing improves ecosystem services (ES) remain poorly understood. Using literature synthesis and quantitative analysis, the worldwide types, distributions, major benefits and issues of terracing are presented in this review. A key terracing indicator, defined as the ratio of different ES under terraced and non-terraced slopes (δ), was used to quantify the role of terracing in providing ES. Our results indicated that ES provided by terracing was generally positive because the mean values of δ were mostly greater than one. The most prominent role of terracing was found in erosion control (11.46 ± 2.34), followed by runoff reduction (2.60 ± 1.79), biomass accumulation (1.94 ± 0.59), soil water recharge (1.20 ± 0.23), and nutrient enhancement (1.20 ± 0.48). Terracing, to a lesser extent, could also enhance the survival rates of plant seedlings, promote ecosystem restoration, and increase crop yields. While slopes experiencing severe human disturbance (e.g., overgrazing and deforestation) can generally become more stable after terracing, negative effects of terracing may occur in poorly-designed or poorly-managed terraces. Among the reasons are the lack of environmental legislation, changes in traditional concepts and lifestyles of local people, as well as price decreases for agricultural products. All of these can accelerate terrace abandonment and degradation. In light of these findings, possible solutions regarding socio-economic changes and techniques to improve already degraded terraces are discussed.