2.2. Experimental design and measurements
An 80 m × 16 m experimental plot was established that included
three subplots along its length. In sequence, these were a spring
wheat subplot, a shelterbelt subplot, and a maize subplot with length
of 22, 36, and 22 m, respectively (Fig. 2). Thus, the shelterbelt was bordered
to the south by spring wheat and to the north by maize. The shelterbelt
had nine rows of Gansu Poplars, which were planted in 1980