Siberian larch also dominates the forest-steppe ecotone. A mixed-grass prairie is an ecotone located between the tallgrass prairies and shortgrass prairies. Estuaries form a transition zone between river environments and maritime environments known as ecotone. An ecotone is a transition area between two biomes. This species is common in the ecotone between woodlands and wetlands. Of these, 728 (23.6%) are in the treeline ecotone. They often nest near the northern limit of tree growth in the forest-tundra ecotone. At an ecotone, species abundances change relatively quickly compared to the environmental gradient. This conjunction constitutes an ecotone, which is rich in species of both ecosystems. Therefore, an ecotone can create a diverse ecosystem. A type of boundary is the "ecotone", or the transitional zone between two communities. The lack of trees causes an ecotone, or boundary, that is obvious to observers. Third, a change of species can signal an ecotone. An ecotone is often associated with an ecocline&colon; a "physical transition zone" between two systems. There are several distinguishing features of an ecotone.