(i) Define pioneer species

(i) Define pioneer species.
(ii) Among bryophytes, lichens and fern, which one is a pioneer species in a xeric succession? And why?

(i) The species that invade a bare area are called pioneer species.
(ii) In a xeric succession the pioneer species are usually lichens then bryophytes, which are succeeded by ferns and some other bigger plants. Lichen produces lichen acid and carbonic acid which corrode rock surface and release minerals required for growth. The corroded rock accumulates soil particle by wind and provides substrafe for bryophytes and ferns.