What kind of succession organisms such as grasses and lichens are classified as?

Organisms such as grasses and lichens are classified as pioneer species in ecological succession. They are typically the first to colonize disturbed or barren environments, helping to establish soil and create conditions suitable for other plants to grow. Their presence is crucial in the early stages of succession, as they contribute to soil formation and nutrient cycling. Over time, they pave the way for more complex plant communities to develop.