The article is consecrated to showing up the fire role in the temperature regime change between between soil and atmosphere parts of ecosystems. The investigations were realized in Russian Middle Priamurie coniferodecidious ecotone. The system of temperature gradient indexes is worked out. The main index of fire impact is a state of soil cover. Under the fire influence the soil cover become degraded. As a result the temperature gradient between soil and atmosphere ecosystem parts decreases. This makes the organism existence conditions more extremal, leads to modification of species composition, changes the environment and induces the disafforestation.