Response of Spring Maize Growth Stage to Climate Change in Northeast China over the Past 30 Years

Northeast China is the main producing area of spring maize. Study on the response of spring maize growth stages to climate change has important significance for the agricultural production in Northeast China.Based on observations of spring maize at 55 agricultural meteorological stations, and daily meteorological data of 16 meteorological stations in Northeast China, combined with generally accepted indicators of agricultural meteorology, as well as the law of growth and development of spring maize, significant meteorological factors affecting the spring maize growth are determined at three time scales of inter-annual, potential growing season and crop growth stages. Variations of spring maize growth stages in Northeast China over the past 30 years are analyzed, using methods of trend rate, spearman correlation analysis, principal component analysis and structural equation modeling. Relationships between maize growth stages and climate change are explored. Finally, responses of spring maize growth stages to meteorological factors over the past 30 years are further analyzed at different time scales.The result shows that spring maize critical growth stages in Northeast China over the past 30 years are postponed. Compared to the stage of tasseling, delaying trends at sowing stage and maturation stage are obvious in most areas. The number of days decreases during the early maize growth stages, while both the late maize growth stages and growth stages extend. In most years, the sowing date of spring maize is later than suitable planting date, and the maturating date is earlier than the first frost date, reducing risks. Under climate warming, the late-maturating maize can be expanded in these areas in order to improve the utilization of thermal resource. Responses of spring maize growth stages to temperature factors are the most notable during the past 30 years.The result by principal component analysis shows that the increased temperature at the inter-annual timescale, the prolonged temperature growth period and the high temperature on the crop growth stages are more notable than other meteorological factors. While, in the structural equation modeling, effects of temperature factors on growth stages are partly indirect, and significant meteorological factors can explain 44% of variation in growth stages. Results deepen understanding effects of climate change on crop mechanism, and can be used as scientific basis for adaptation to climate change in the future.