Growing degree days (GDD) and chilling requirements (CR) of canopy phenological onset are popular thermal indicators showing forest adaptation to local temperature regimes. This study proposes a satellite-based approach for mapping the canopy-onset thermal traits and analyzing their controlling factors in temperate forests. GDD and CR from 2003 to 2017 were estimated with canopy onset dates and air temperature data retrieved from Moderate Resolution and Imaging Spectroradiometer (MODIS) images. Results revealed that GDD and CR showed distinct geographic patterns with latitude and altitude but with low inter-annual variations of less than 30% of the coefficient of variation. The satellite-based spatial patterns of GDD and CR were well explained by temperature with R-squares of 0.70 and 0.58, which were comparable to 0.63 and 0.59 from the field observation data, respectively. As well, satellite-derived sensitivities of GDD and CR to unit changes in temperature were +52.7 and −21.3°C^oC⁻¹, respectively, which were again comparable to the sensitivities from the field data (+50.9 and −29.9°C^oC⁻¹, respectively). The patterns and temperature dependency of thermal parameters seem to be relevant to species-level thermal acclimation and community-level plant composition changes with temperature.

冠层物候发生的生长日数（GDD）和降温要求（CR）是流行的热指标，表明森林对当地温度状况的适应性。这项研究提出了一种基于卫星的方法，用于绘制温带森林中冠层开始的热性状并分析其控制因素。根据2003年至2017年的GDD和CR估算了树冠的发病日期和从中等分辨率和成像光谱仪（MODIS）图像中检索到的气温数据。结果表明，GDD和CR显示出不同的地理模式，包括纬度和高度，但年际变化较小，不到变异系数的30％。用温度很好地解释了GDD和CR的基于卫星的空间格局，R平方分别为0.70和0.58，与0.63和0相当。分别来自现场观察数据的59个。同样，卫星得出的GDD和CR对温度单位变化的敏感度分别为+52.7和-21.3°C分别为^o C ^-1，这再次与现场数据的灵敏度相当（分别为+50.9和-29.9°C ^o C ^-1）。热参数的模式和温度依赖性似乎与物种水平的热适应和社区水平的植物组成随温度的变化有关。