了解植物生根深度对于了解植物介导的全球变化至关重要。 地球系统模型对这一特定参数非常敏感，对模拟植物生产力，土地和大气之间的水能 - 碳交换以及调节数百万年间碳循环的硅酸盐风化影响很大。 然而，我们对于植物根系能长多深及其原因却知之甚少。 偶然间的发现：根系在井中深度>70m, 而在山洞中根深却只>20m,表明植物根系具有巨大可塑性，但其驱动因素和全球意义尚不清楚。 Fan等研究人员通过对1000多种植物根系观测和建模分析，揭示了土壤水分是植物生根深度总体模式形成的最普遍的驱动力。

该论文发表于PNAS，2017年第114卷40期上，doi: 10.1073/pnas.1712381114

Hydrologic regulation of plant rooting depth

Plant rooting depth affects ecosystem resilience to environmental stress such as drought. Deep roots connect deep soil/groundwater to the atmosphere, thus influencing the hydrologic cycle and climate. Deep roots enhance bedrock weathering, thus regulating the long-term carbon cycle. However, we know little about how deep roots go and why. Here, we present a global synthesis of 2,200 root observations of >1,000 species along biotic (life form, genus) and abiotic (precipitation, soil, drainage) gradients.Results reveal strong sensitivities of rooting depth to local soil water profiles determined by precipitation infiltration depth from the top (reflecting climate and soil), and groundwater table depth from below (reflecting topography-driven land drainage). In well-drained uplands, rooting depth follows infiltration depth; in waterlogged lowlands, roots stay shallow,avoiding oxygen stress below the water table; in between, high productivity and drought can send roots many meters down to the groundwater capillary fringe. This framework explains the contrasting rooting depths observed under the same climate for the same species but at distinct topographic positions. We assess the global significance of these hydrologic mechanisms by estimating root water-uptake depths using an inverse model, based on observed productivity and atmosphere, at 30″ (∼1-km) global grids to capture the topography critical to soil hydrology. The resulting patterns of plant rooting depth bear a strong topographic and hydrologic signature at landscape to global scales. They underscore a fundamental plant–water feedback pathway that may be critical to understanding plant-mediated global change.