The subterranean lithic biome includes non-aquatic lithic systems beneath the earth’s surface.

Sunlight is absent or of insufficient intensity to sustain photosynthesis. There is no standing water and moisture is supplied primarily by seepage through the substrate and may be lost by slow diffusion through the atmosphere to cave openings or by vertical or lateral seepage through the substrate. These physically stable systems exhibit low levels of environmental variability. Rarely, mass movements, for example rock falls, may re-organise the physical structure of subterranean ecosystems.

Subterranean ecosystems have truncated trophic structures with no photoautotrophs and few obligate predators. Heterotrophic microbes and invertebrates dominate the biota, while chemoautotrophs are the primary energy assimilators. Most have low metabolic rates and prolonged life histories in response to resource limitations, resulting in low overall productivity.

The subterranean biome includes dry caves and endolithic systems distributed throughout the earth’s crust. Incursions of fresh or marine waters generate transitional biomes (SF1, SM1).