Abstract. The land cover and management changes have strong feedbacks to climate through surface biophysical and biochemical processes. Agricultural phenology dynamic exerted measurable impacts on land surface properties, biophysical process and climate feedback in particular times at local/regional scale. But the responses of climate feedback through surface biophysical process to sowing date shift in the winter wheat ecosystem have been overlooked, especially at winter dormancy period. Considering the large cultivation area, unique surface property and phenology shift of winter wheat in the North China Plain, we first validated the SiBcrop model. Then, we used it to investigate the dynamics of leaf area index (LAI) and canopy temperature (T_c) under two planting date scenarios (Early Sowing: EP; Late Sowing: LP) of winter wheat at 10 selected stations. Finally, the surface energy budget was analyzed and interpreted. The results showed that the SiBcrop with a modified crop phenology scheme better simulated the seasonal dynamic of LAI, T_c, phenology, and surface heat fluxes. Earlier sowing date had higher LAI with earlier development than later sowing date. But the response of T_c to sowing date exhibited opposite patterns during the dormancy and active growth periods: EP led to higher T_c (0.05 K) than LP in the dormancy period and lower T_c (−0.2 K) in the growth period. The highest difference (0.6 K) between EP and LP happened at the time when wheat was sown in EP but wasn't in LP. The higher LAI captured more net radiation with lower surface albedo for warming, whist surface energy partitioning exerted cooling effect. The relative contributions of albedo-radiative process and partitioning-non-radiative process determined the climate effect of sowing date shift. The spatial pattern of the climate response to sowing date was influence by precipitation and air temperature. The study highlight that the climate effects of the sowing date shift in winter dormancy period are worthy of attention.

中文翻译：

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华北平原冬小麦生育期和休眠期至播种期变化的气候反馈不同

摘要。土地覆盖和管理变化通过表面生物物理和生化过程对气候有强烈的反馈。农业物候动态对地方/区域尺度的特定时期的土地表面特性，生物物理过程和气候反馈产生了可测量的影响。但是，人们忽略了通过表面生物物理过程产生的气候反馈对冬小麦生态系统中播种日期变化的响应，特别是在冬季休眠期。考虑到华北平原冬小麦的大面积种植，独特的表面特性和物候变化，我们首先验证了SiBcrop模型。然后，我们用它来研究叶面积指数（LAI）和冠层温度（T _c）在10个选定站的两个播种日期情景下（早播：EP；晚播：LP）。最后，对表面能收支进行了分析和解释。结果表明，采用改良的作物物候方案的SiBcrop可以更好地模拟LAI，T _c，物候和表面热通量的季节动态。较早播种，较早播种的LAI更高。但是在休眠期和生长活跃期，T _c对播种的反应表现出相反的模式：EP导致休眠期的T _c（0.05 K）高于LP，而较低的T _c（-0.2 K）在生长期。EP和LP之间最大的差异（0.6 K）发生在EP中播种小麦，而LP中则没有。较高的LAI捕获了更多的净辐射，而较低的地表反照率则使地球变暖，而表面能量的分配则起到了降温的作用。反照率辐射过程和分区非辐射过程的相对贡献决定了播种日期变化的气候效应。播期气候响应的空间格局受降水和气温的影响。该研究强调，冬季休眠期播种日期变化的气候影响值得关注。