| Drought disasters bring great loss to human life and industrial and agricultural production. As the world’s arid and semi-arid phenomenon was increasingly serious, agricultural drought monitoring has become a research hotspot. Based on the field experiment in the large moving water proof canopy, the effect of water stress on the ecophysiological characteristics of summer maize in different growth periods and its dynamic variation rule were analyzed to provide technical guidance to agricultural water conservation work. The primary conclusions are as follows:(1) Under water stress, plant height, leaf area, biomass and grain yield were reduced. Corn SPAD, photosynthetic rate, transpiration rate and stomatal conductance decreases as water stress intensified, while the canopy temperature and water use efficiency increased significantly.(2) Diurnal variation of photosynthetic rate, transpiration rate both appeared bimodal curves, and the peak occurred at11:00and15:00. The diurnal variation of stomatal conductance presented a single curve which peak was at11:00. The diurnal variation of canopy temperature curve had bimodal peaks appearing at12:00and14:00.The photosynthetic response data of maize was fitted using quadratic regression method, rectangular hyperbolic model and non-rectangular hyperbola model. The result showed that the maximum photosynthetic rate of corn, light saturation point and apparent quantum yield decreased under water stress, while light compensation point rose.Jarvis nonlinear stomatal conductance model joining soil moisture was simulated better to reflect the response between the leaf stomatal conductance and environmental factors.(3) The curve shapes of canopy spectral reflectance under different soil moisture conditions are essentially similar with differences in each band. The canopy reflectance of maize in visible (380～710nm) and near medium&long infrared spectrum regions (1100～2500) was increasing with the decreasing of soil water, while decreasing in the near-infrared shortwave domain (750～1100nm). The ratio vegetation index (RVI) and normalized difference vegetation index (NDVI) were reducing under water stress. There were exponential functions and significantly correlations between NDVI&RVI and SPAD&LAI&stomatal conductance of leaf or canopy leaf. Beside, NDVI fitted into SPAD&LAI better than RVI.(4) The daily variation of soil respiration rate under different water treatments showed a bimodal curve with the maximum appearing at13:00and15:00. The soil respiration rate decreased significantly with the decline of soil moisture. Soil temperature and soil moisture were the dominant environmental factors of soil respiration. The coefficients of soil respiration models in two factors were more than92%. The exponential model explained better than the line models. |
PDF Full Text Request