Explanation : (A) Hydrarch succession - (IV) Phytoplankton to mesic conditions. Hydrarch succession occurs in wet or aquatic areas, starting from an aquatic stage like phytoplankton and gradually moving towards mesic conditions, where the environment is neither too wet nor too dry. (B) Xerarch succession - (III) Lichens to mesic conditions. Xerarch succession occurs in dry areas, such as deserts or rocks, and typically begins with organisms like lichens, gradually moving towards mesic conditions. (C) Ecological succession - (I) Gradual change in the species composition. Ecological succession is the process by which the structure of a biological community evolves over time, involving a gradual change in species composition. (D) Secondary succession - (II) Faster and climax reached quickly. Secondary succession refers to the series of community changes that occur on a preexisting, disrupted habitat and is typically faster than primary succession with the climax being reached more quickly because it begins on soil and not bare rock.