The species that invade a bare area are called pioneer species. In primary succession in xerarch these are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation. Xerarch is ecological succession in dry areas. As a result of succession, forests are established as climax community. Hydrach is the succession in water and it starts with phytoplanktons, goes through submerged plants, submerged free floating plants, reed swamp stage, marsh meadow stage, scrub stage to forest stage as climax community.