Pioneer species are hardy
species which are the first to
colonize previously disrupted or damaged
ecosystems, beginning a chain of
ecological succession that ultimately leads to a more biodiverse
steady-state ecosystem. Some
lichens grow on rocks without soil, so may be among the first of life forms, and break down the rock into soil for other plants. Since some uncolonized land may have thin, poor quality soils with few nutrients, pioneer species are often hardy plants with adaptations such as long roots, root nodes containing
nitrogen-fixing bacteria, and leaves that employ
transpiration. Pioneer species will die creating
plant litter, and break down as "
leaf mold" after some time, making new soil for
secondary succession (see below), and nutrients for small fish and
aquatic plants in adjacent bodies of water.