Different conservation values and perspectives can lead to divergent conservation objectives. Understanding such differences is crucial to developing more comprehensive and inclusive conservation approaches. Using plots, we assessed how numbers of useful species as reported by indigenous forest-dwelling people relate to plant species richness. We used 173 plots recording both trees and herbaceous vegetation and the knowledge of both Merap- and Punan-dominated communities in Malinau, Kalimantan (Indonesian Borneo). We used general linear models (GLMs) to characterise the relationships. Useful species increase with species richness in all cases. The relationship varied across culture and community and was not always linear. The proportion of tree species reported as useful by Merap (primarily agriculturalist) informants was not constant but declined significantly as plot diversity increased; this was not the case for Punan (primarily hunter-gatherer) informants. There was no decline for the reported proportion of useful herbs as richness increases, as assessed by either ethnic group. Communities with less wealth and less schooling generally reported a higher proportion of the useful species. We interpret these results in terms of how landscape patterns of plant diversity are experienced. Understanding of these relationships can help us develop a more explicit approach to weighing and reconciling different conservation values and management objectives in changing forest landscapes.