DENDROLOGY

Detailed explanation-1: - 4.Herb stage-the soil increases in thickness, Herbaceous weeds, mostly annuals such as asters, evening primroses, and milk weeds, invade the rock. Their roots penetrate deep down, secrete acids and enhance the process of weathering. Leaf litter and death of herbs add humus to the soil.

Detailed explanation-2: -Primary succession is ecological succession that begins in essentially lifeless areas, such as regions in which there is no soil or where the soil is incapable of sustaining life (because of recent lava flows, newly formed sand dunes, or rocks left from a retreating glacier).

Detailed explanation-3: -Primary succession occurs when new land is formed or rock is exposed; for example, following the eruption of volcanoes, such as those on the Big Island of Hawaii.