DENDROLOGY

Detailed explanation-1: -The labels I-VII represent the different stages of primary succession. I-bare rocks, II-pioneers (mosses, lichen, algae, fungi), III-annual herbaceous plants, IV-perennial herbaceous plants and grasses, V-shrubs, VI-shade intolerant trees, VII-shade tolerant trees.

Detailed explanation-2: -Lichens are considered as pioneer species in primary succession on rocks because they can easily grow on rocks where other plants cannot grow. They produce oxalic acid which induced the weathering of rocks and thus soil is formed.