2.3. Experimental design
In order to enhance the ability of jujube trees to resist extreme seasonal droughts, a mulching experiment was conducted at this site in 2013. First, branches pruned from jujube trees during normal management and maize stems were trimmed to lengths of approximately 20 cm and then used as mulch on the surface of half-moon terraces, applied at a thickness of 15 cm, resulting in two combinations of terracing and mulching (Figure S1), hereafter JBT and MST, respectively. The mulch material can be washed off the terraces by rapid overland flow during heavy rainstorms or blown away by strong winds. Therefore, new branches or maize stems were added to terraces every spring to maintain a constant thickness. Two other treatments, just half-moon terracing (SHT) and the traditional hillslope (control) land management practices, were also examined. Each treatment included four replicates, and each replicate comprised a 24-m2 plot (4 m × 6 m), including three jujube trees. Therefore, there was a total of 16 plots in the experiment.