A mechanistic examination of diversity-stability relationships in annual plant communities

• Published in: Oikos Vol. 103; no. 3; pp. 519 - 527
• Main Authors: Valone, Thomas J., Hoffman, Catherine D.
• Format: Journal Article
• Language: English
• Published: Copenhagen Munksgaard International Publishers 01.12.2003; Blackwell Publishers; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Annuals; Biodiversity; Biological and medical sciences; Communities; Community relations; Ecosystems; Fundamental and applied biological sciences. Psychology; Plant communities; Species; Species diversity; Summer; Synecology; Terrestrial ecosystems; Winter; Species diversity; Stability; Plant community; Annual plant; Spatial scale; Biodiversity; Comparative study
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1034/j.1600-0706.2003.12279.x

While recent theoretical work has demonstrated several mechanisms whereby more diverse communities can exhibit greater temporal stability, empirical examinations have been few and the subject of much debate. We show that the temporal stability of natural summer and winter annual plant communities, at spatial scales of 0.25 m2 and 0.25 ha, tends to increase with community richness. Furthermore, more diverse communities exhibited greater stability because they contained a greater abundance of individuals (overyielding effect). Statistical averaging (the portfolio effect) and negative covariances between species (insurance and competition effects) did not enhance stability. Relationships between diversity and stability tended to be weak and were significant only at the smaller spatial scale. Because more diverse communities contained higher densities of individuals, the effect of diversity per se on stability was unclear and likely small. If overyielding is common in other ecological systems, the loss of individuals and biodiversity may often result in increased variation in ecological communities.