The microclimate dynamics under forest crown fundamentally drive plant community responses to global warming. The understory air and soil temperatures are two of the most important components of forest understory microclimate. However, there is rare method to reasonably evaluate the joint effects of forest cover on the understory air and soil temperatures. In this study, we combined a novel three-layer energy balance model and intrinsic biophysical mechanism model to evaluate the biophysical effects of forest on air ($\Delta T_a$) and soil temperatures ($\Delta T_s$) under forest crown at the global scale. Observations from in situ paired expariments and eddy covariance sites from FLUXNET 2015 were used for validations over the globe. The warming effect caused by low albedo and cooling effect caused by large aerodynamic roughness of forest lands mainly explain the global patterns of $\Delta T_{\mathrm{s}}$ and $\Delta T_{\mathrm{a}}$, which indicate mostly a net cooling in low latitudes, but show opposite directions in large parts of temperate and high latitudes. The ratios of aerodynamic resistance of sensible heat fluxes between upper and lower layers show a positive relationship with $\Delta T_{\mathrm{s}}$ and $\Delta T_{\mathrm{a}}$. The Bowen ratio is negatively related to $\Delta T_{\mathrm{s}}$, but is positively related to $\Delta T_{\mathrm{a}}$, respectively. Additionally, we examined a new indicator, which is composed of both $\Delta T_{\mathrm{s}}$ and $\Delta T_{\mathrm{a}}$ and regulated by the aerodynamic resistance parameters, to evaluate the joint biophysical effects of forest on understory air and soil temperatures. This study fills the gap in modeling the biophysical effects of forest on air and soil temperatures under forest crown over the global scale and improves our understanding of the mechanisms governing the biophysical effects of global forest cover on understory microclimate.

林冠下的小气候动态从根本上推动植物群落对全球变暖的反应。林下空气和土壤温度是林下微气候的两个最重要组成部分。然而，很少有方法可以合理评估森林覆盖对林下空气和土壤温度的联合影响。在这项研究中，我们结合了一种新的三层能量平衡模型和内在生物物理机制模型来评估森林对空气的生物物理效应。$\Delta {吨}_{\mathrm{一种}}$) 和土壤温度 ($\Delta {吨}_{秒}$) 在全球范围内的林冠下。从观察现场配对expariments，并从2015年FLUXNET涡动相关网站被用于全球各地的验证。低反照率引起的增温效应和林地空气动力粗糙度大引起的降温效应主要解释了全球气候变化规律。$\Delta {吨}_{\mathrm{秒}}$ 和 $\Delta {吨}_{\mathrm{一种}}$，这表明在低纬度地区主要是净冷却，但在温带和高纬度地区的大部分地区显示出相反的方向。上、下层感热通量气动阻力比值与$\Delta {吨}_{\mathrm{秒}}$ 和 $\Delta {吨}_{\mathrm{一种}}$. 鲍温比率与$\Delta {吨}_{\mathrm{秒}}$，但与 $\Delta {吨}_{\mathrm{一种}}$， 分别。此外，我们检查了一个新指标，它由$\Delta {吨}_{\mathrm{秒}}$ 和 $\Delta {吨}_{\mathrm{一种}}$并受空气动力学阻力参数调节，以评估森林对林下空气和土壤温度的联合生物物理效应。这项研究填补了在全球范围内模拟森林对森林冠下空气和土壤温度的生物物理影响的空白，并提高了我们对控制全球森林覆盖对林下小气候生物物理影响的机制的理解。