Based on the systematic investigation of root development characteristics of vegetation with multi-lithologic gradients in the Qinling Mountains, the academic viewpoint of "Ecological Rooting Zone (ERZ)" was put forward to characterize the vertical structural functional zone of rock-soil-water that sustains both the stabilizing anchorage and prolific growth of mountain root systems. The essential properties, spatial range, vertical structure, horizontal differentiation characteristics and the various elements coordination and coupling mechanism of ERZ were clarified by elaborating the elements composition, developmental characteristics and mechanism of ERZ. At the same time, the differences and connections between the ERZ and similar concepts such as the Earth"s Critical Zone and the Ground Substrate Layer were compared and contrasted. The viewpoints obtained were as follows: (1) ERZ was a key zone connecting earth"s surface ecosystem and lithosphere layer for material and energy exchange, and its ecological geological characteristics determined the growth pattern and quality of earth"s surface vegetation. (2) The depth range of ERZ was defined as the deepest vertical distance from the earth"s surface to the root development of vegetation, and there were obvious differences due to the weathering resistance of different lithologies. (3) The vertical structure of ERZ can be divided into shallow root system-humus interaction layer, main straight root system-weathering zone support layer, and deep root system-bedrock fissure anchorage layer. Different depth domains played different roles in root mechanical remould, fissure hydrodynamic transmission, and mineral nutrient release. Meanwhile, the horizontal differentiation of ERZ was the adaptive response behavior of the root system to the coordination of soil, geomorphology and hydrology. (4) The coordinated coupling of bedrock, fissure, root system and hydrology controls and influences the development characteristics of ERZ. The properties of bedrock controlled the spatial distribution of ERZ, fissure development restricted the vertical structure of ERZ, hydrological conditions guide the horizontal stratification of ERZ, and root competition regulated the development morphology of ERZ. (5) In compared and contrasted to similar academic concepts in related fields, the ERZ was primarily dominated by vegetation root growth, focusing on the vertical continuous area from shallow surface to bedrock fissure, and emphasized the dynamic co-evolution mechanism of ecological and geological elements. The academic viewpoint of ERZ breaks through the previous simplistic understanding of the "root-soil interface" and extended the perspective to the co-evolutionary framework involving root growth space and bedrock-fissure-hydrology interactions. It provided a theoretical basis for understanding how geological factors participate in the ecological process of mountain vegetation.