Periodicity of plant yield and its response to precipitation in the steppe desert of the Tianshan Mountains region

Plant yield and precipitation data from 23 to 29 years of field-based work were used to investigate the periodicity of the annual yield of Seriphidium-steppe desert (wormwood grassland) and its response to precipitation change in the lower Tianshan Mountains region, western China. There were very similar variations in annual yield (dry matter) of steppe desert with precipitation changes in most years. The annual yield (y) was estimated from precipitation (x) by a significant (P < 0.01) regression model: y = −368.52 + 3.07x, averaged 736.35 kg/ha, with 359.91 mm precipitation, in the Seriphidium-gramineal grassland; and y = −420.58 + 3.5653x (P < 0.01), Averaged 472.5 kg/ha, with 252.2 mm precipitation, in the Seriphidium-grassland, respectively.The spectral analysis of these data revealed the highest probability of a 10 year periodic cycle of annual yield and only a weak cycle of 6 year and then 16 year period of the annual precipitation in the Seriphidium-gramineal grassland. Similarly, there was a high probability of a 10–12 year periodic cycle of annual yield and a 16 year cycle of annual precipitation in the Seriphidium-grassland. The different periodic patterns of plant yield in the study area indicated a prolonged periodic cycle of plant production when climate becomes drier.