Grasslands often contain a great diversity of plants called plant diversity. This diversity is of interest to the botanist for the conservation of wild species, to the agronomist for a diversified fodder resource in relation with the quality of food products, to the entomologist for the resources it provides to insects (habitat). This plant diversity can be studied with different approaches:

Species diversity aims to establish an exhaustive list of species present in a grassland and their abundance. Ecologists and botanists use it to characterize habitats. It informs on ecological conditions or the patrimonial status of communities, but is not very precise on the agronomic value of grasslands (productivity, quality, precocity, …).

Functional diversity aims to identify the main types of plant species present in a grassland. Species recorded during a survey are then considered according to their biological characteristics (called functional traits) which correspond to similar functioning or strategies. For example, agronomists use functional diversity to characterize the agronomic value of grasslands. Thus, a grassland with a highly functional diversity shows a high resilience to extreme events and can be exploited in a flexible way.

Genetic diversity aims to establish the list of varieties or genes present within a given species. For instance, plant breeders use it to offer varieties with distinct and complementary agronomic characteristics.

One of the challenges of agroecology is to take advantage of plant diversity to support agricultural production while contributing to the conservation of biodiversity. In the Midi-Pyrénées region, permanent grasslands contain more than 600 species, it is therefore a reservoir of biodiversity which provides many ecosystem services to animal breeders (productivity, grass quality, …), and to society (erosion, carbon sequestration, …). Complementary approaches conducted by agronomists, botanists and ecologists contribute to a better understanding of factors that influence plant diversity and its role.