Effects of land preparation and plantings of vegetation on soil moisture in a hilly loess catchment in China

In the dryland and degraded regions, soil moisture is the primary factor determining ecological restoration. Proper land preparations and vegetation restoration can improve soil moisture and benefit land restoration. Identifying their effects on soil moisture is thus essential for developing suitable management strategies. In this study, four typical land preparation techniques (level ditches, fish-scale pits, zig terraces, and level benches) and non-native vegetation types (Prunus armeniaca, Platycladus orientalis, Pinus tabulaeformis, and Caragana microphylla) were planted on a semiarid loess hilly catchment, China. Soil moisture was monitored by a time-domain reflectometer, and its spatial-temporal variations were analyzed during the 2014-2015 growing seasons. The following results were captured. (a) Soil moisture was highest for the combination of P.orientalis and fish-scale pits (P.orientalis/fish-scale pits, 10.37%), followed by P.armeniaca/level ditches (10.23%), P.orientalis/zig terraces (9.67%), C.microphylla/level benches (8.62%), P.tabulaeformis/fish-scale pits (8.05%), and P.tabulaeformis/zig terraces (7.72%). (b) Fish-scale pits offered a better rainwater-harvesting capacity during the rainy months, whereas zig terraces had a higher water retention capacity under extremely dry conditions (as indicated by the temporal soil moisture variation and soil water retention curves). (c) P.tabulaeformis consumed more water than other vegetation types (26.7% lower than that of P.orientalis). (d) Soil moisture in shallower layers (0-80cm) was more affected by land preparations and was more effected by vegetation types in deeper soil layers (80-180cm). We thus suggest that fish-scale pits may be a better choice in wetter regions whereas zig terraces and P.orientalis are more suitable in the driest parts of the Loess Plateau to restore the fragile ecosystems.