Species richness Number of different species occurring in a particular ecological community Primary productivity Amount of energy produced or autotrophs in a community Primary succession Establishment of a new community on a site that was previously unoccupied by life, like lava flow Secondary succession Development of a community on previously occupied sites following a disturbance, like an old field Organismal concept A view of the community analogous to a complex, living being Individualistic concept A view of communities as a unique group of species growing along an environment gradient Landscape ecology The study of how different communities interact and change over large areas Biological legacies These occur when root or seed species persist and re- grow after disturbance in a community Early-seral species Short-lived colonizing plant species in succession, usually annually Late-seral species Slow-growing, long-lived species in succession, usually perennial