Observation And Simulation Study On Maize Growth And Yield Under Climate Change In Northeast China

At present, the study methods on the impacts of future climate change on agricultural production are mainly concentrated in two aspects i.e., observation and simulation. To the effects of climate change on Maize yield as the center, we observed and simulated the effects of different climatic factors and future climate conditions on Maize production in Northeast China from single site to the region. First of all, we conducted two field experiments with elevated [CO2] and warming manipulated by Open Top Chambers (OTCs) and Free Air Temperature Increase (FATI), while the effects of [CO2], temperature, precipitation, and their interactive effects on Maize yield were observed systematically and comprehensively during whole growth period from morphology, photosynthesis, dry weight accumulation and phenology. Then, based on the observation data, CERES-Maize model was used to simulate the Maize yield under the interactive effects of a series of precipitation gradient, temperature, and [CO2]. Finally, the regional climate model (BCC_CSM1.1-RegCM4.0) and CERES-Maize model were linked to simulate the spatial distribution of Maize yield under the future climatic conditions in Northeast China. The main conclusions are listed as follows.(1) There were significantly increase in seed yield and biological yield of Maize under the interactive effects of elevated [CO2] and precipitation. The increase differ for different [CO2] and precipitation, e.g., the yield under the interactive effects of 550μmol·mol-1[CO2] and precipitation of the highest,450μmol·mol-1[CO2] second, and 390μmol·mol-1[CO2] minimum. Also, the ear characteristics of Maize significantly changed under the interactive effects, e.g., kernal number, keraal weight, ear length and ear diameter were increased. These changes were external performance of increasing yield, which reflected the expansion of Maize ear capacity. In addition, the leaf net photosynthetic rate (Pn), water use efficiency (WUE), maximum net photosynthetic rate (Pnmax), light saturation points (LSP) and the content of chlorophyll increased, whereas the transpiration rate (Tr) and stomatal conductance (Gs) decreased with the interactive effects, that of changes explained the internal physiological mechanisms of increasing yield. The growth characteristics, e.g., plant height, stem diameter and leaf area were enhanced, resulting in an improved of yield.(2) Maize whole growth period shortened and seed yield decreased under the interactive effects of warming and increased precipitation. For example, the ear length, ear weight, kernel number and kernels per row significantly decreased (p<0.05), whereas that of shriveled kernels and bare-tip length increased (p<0.05). Warming had a negative effect on Pn, T1, GS, Pnmax and LSP, and the precipitation had a positive effect on them, but the condition of warming together with increased precipitation could alleviate the negative effect of warming to a certain extent. The growth characteristics, e.g., plant height, leaf area and aboveground biomass were decreased with warming, however, increased precipitation 15% can increased them with a small degree, and decreased to a lesser extent under warming and increased precipitation.(3) To simulate the effects of [CO2] and precipitation on Maize, precipitation were divided into two cases i.e., precipitation during the whole growth period and each growth period. In the case of precipitation during the whole growth period, seed yield increased with precipitation and [CO2], and the seed yield reached peak when precipitation increased 30% in all [CO2] treatments. Moreover, in the case of precipitation during each growth period, the impact on yield higher at Maize silking stage and milky stage, but seedling stage and joining stage minimum. In addition, the seed yield of Maize decreased under the together effects of elevated [CO2], warming and precipitation.(4) The regional climate model (BCC_CSM1.1-RegCM4.0) can provide input climate data for crop model. The study introducted and linked this model with CERES-Maize model, and obtained an ideal effect by simulating test, which shows that the BCC_CSM1.1-RegCM4.0 model can provide future daily meteorological data for crop model.(5) Comparing with 1971～2000, there is a decreasing trend on Maize yield in most of regions in Northeast China, whereas increasing in other local regions in 2036～2065. The yield increased highest by 14.17% and decresed lowest by 17.50%. Additionally, the yield increased areas expand to northeast of Jilin Province and south of Heilongjiang Province, while there is an increasing trend in northern Heilongjiang Province.(6) Climate change will drastically in Northeast China in the future, e.g., the average annual maximum temperature and minimum temperature will increase significantly, and decrease from south to north gradually in spatial distribution. The spatial distribution of precipitation is uneven, which decrease from southeast to northwest. The average annual solar radiation will reduce in most of regions, but increase in some local areas, which reduce from west to east gradually.