Drainage of paddy terraces impacts structures and soil properties in the globally important agricultural heritage of Hani Paddy Terraces, China

Marginalization and abandonment of paddy terraces are widespread, but their effects on the sustainability of subsequent agricultural production are still unknown. Hani Paddy Terraces, included in Globally Important Agriculture Heritage Systems, are threatened by paddy fields drainage. Here, changes in terrace structure, the productivity of topsoil (0–20 cm), and soil water holding capacity at 0–70 cm depth were determined in a case study of Hani Paddy Terraces in Amengkong River Basin in Yuanyang County in Southwestern China, which had been converted into dryland terraces for 2–14 years. Our results showed that: (1) The degree of terrace structures degradation exhibited a U-shaped curve with increasing time since draining, with those drained for 5–9 years having the best structure; (2) Soil productivity index decreased first and then increased with time after conversion; (3) Maximum water holding capacity at 0–70 cm soil depth dramatically decreased after conversion and such trend became increasingly obvious with increasing time since conversion. Our study revealed that drainage of paddy terraces along with associated changes in crop and field management led to an increase in soil productivity, but degradation of terrace structures and a decrease in water holding capacity will inhibit restoration to paddy terraces. These findings enhance the understanding of the biophysical changes due to marginalization in paddy terraces.