Effects of terracing on root distribution of Pinus tabulaeformis Carr. forest and soil properties in the Loess Plateau of China

Abstract

Terracing is one of the most effective ecological engineering practices that improve soil anti-erosivity properties and support plant growth in the dryland loess hilly area and other similar regions. The objective of the study was to understand the vertical distribution of root in different terraces and their relationships with soil environmental factors in the Loess Plateau of China. The vertical root distribution in the 0–400 cm soil profile, fine root distribution and soil moisture, soil nutrients (soil organic carbon, total nitrogen, and total phosphorus) and soil anti-erosivity in 0–160 cm soil profiles (every 20 cm for one layer) were investigated using the ground-penetrating radar and soil coring methods in a Pinus tabulaeformis Carr. forest under three terrace types during the growing season of 2018. We highlight several key findings here. First, level benches had the highest root density (18.14 kg m−2), followed by fish-scale pits (13.95 kg m−2) and reverse-slope terraces (9.84 kg m−2), as well as the highest soil water content, nutrients and soil stability. Second, terracing caused significant differences in root distribution (P < 0.05), leading to the variation of soil moisture, nutrients, anti-erosivity (explained over 80% variation) and reduced spatial heterogeneities of soil water content and nutrients. Third, fine root density parameters attained the highest values in the topsoil (0–40 cm soil layer) and decreased with increasing soil depth in all the three terrace types (P < 0.05). Finally, fine roots contributed to soil water improvement, nutrient promotion and soil stabilization, while higher density of coarse roots might consume soil nutrients and reduce soil anti-erosivity. We thus suggest that level benches could be a more suitable terracing measure for plantation of P. tabulaeformis Carr., and to achieve soil melioration and fixation during the ecosystem restoration process in the Loess Plateau and other arid and semiarid regions.