华北平原玉米播种期和品种变化对冠层温度的影响及地表生物物理机理

通过改变陆—气界面的地表水热交换,农田管理变化是气候变化的重要反馈过程之一。华北平原玉米的播种期和有效积温发生了规律性变化,改变了叶面积指数(LAI)、地表反照率(α)、净辐射(R_n)、潜热(LH)和冠层温度(T_c)等,成为区域气候变化的重要反馈过程。论文利用SiBcrop模型模拟3种玉米情景(春玉米、夏玉米、潜在玉米)下的LAI、α、R_n、LH和T_c的季节动态。结果表明,春玉米具有早播种、早收获、早LAI峰值的特征;夏玉米具有晚播种、晚收获、晚LAI峰值的特征;潜在玉米具有早播种、晚收获、高LAI的特征。模拟情景之间LAI差异为±2.5 m²·m^-2;T_c差异为±0.5 ℃。地表反照率(α)和地表能量分配是决定情景之间T_c差异的决定因素,播种期推迟,以α升高的降温效应为主;有效积温增加,以LH分配增多的降温效应为主。春玉米具有最高的冠层温度,夏玉米和潜在玉米的冠层温度较低且差异很小。研究结果对于促进农田土地管理变化适应和缓解区域气候变化具有一定意义。

Impacts of maize planting date and variety on canopy temperature on the North China Plain and surface biophysical mechanism

By changing the surface energy and water exchange at the land-atmosphere interface, farmland management change becomes an important feedback process of climate change. The planting date and growing degree day of maize on the North China Plain have changed, which is a potential feedback process for regional climate by influencing leaf area index (LAI), surface albedo (α), net radiation (R_n), latent heat (LH), and canopy temperature (T_c). The SiBcrop model was used to simulate the seasonal dynamics of LAI, α, R_n, LH and T_c under three maize planting scenarios (spring maize, summer maize, and potential maize). The results show that spring maize had the characteristics of early planting, early harvest, and early LAI peak; summer maize was characterized by late planting, late harvest, and late LAI peak; potential maize was characterized by early planting, late harvest, and high LAI. The differences between the simulated scenarios were ±2.5 m²·m^-2 for LAI and ±0.5 ℃ for T_c. The main determinants of T_c difference between the three scenarios were α and surface energy partitioning. The cooling effect of delayed planting was dominated by the increased α; and the cooling effect of prolonged growing degree day was mainly due to the increased LH partitioning. Spring maize had the highest T_c, while summer maize and potential maize had lower T_c with little difference. The results of this study have certain significance for farmland management change for the adaptation to regional climate change and mitigation.