Figure 1. Distribution of sampling sites of annual ephemerals in the desert of northern Xinjiang, China

In the quadrat, we selected 10 plants whose plant height and root collar diameter are similar to the standard plants, and used big shovel, small shovel, 30cm steel ruler, brush and other tools to dig all plant roots in situ with ”trench method”(Shan et al., 2012). That is, a volume of 10cm × 5cm × 40cm trench at a distance of 3-4 cm from the individual plant was dug with big shovel. Then, the soil around the root was cleared into the trench with small shovel. When the larger diameter taproot was exposed, in order to avoid root system damage, we used a steel ruler to continue to clean the soil around the finer root branches. After the root system of plant was completely exposed, the maximum root depth (MRD) of them were measured in situ with a tape measure and recorded it. After that, carefully placed the plant individuals in a plastic bag, and then transported them to store in an ice box back to the laboratory.