Seasonal changes in the relationship between plant species richness and community biomass in early succession

• Published in: Basic and applied ecology 2005-01, Vol.6 (4), p.385-394
• Main Authors: Bischoff, Armin, Auge, Harald, Mahn, Ernst-Gerhard
• Format: Article
• Language: English
• Subjects: Aboveground biomass; Competition exclusion; Diversity; Hump-shaped relationship; Old field; Self-thinning; Temporal dynamics
• ISSN: 1439-1791
• DOI: 10.1016/j.baae.2005.03.003

We analysed the relationship between plant species richness and productivity on first-year-old fields at two similar sites in central Europe. At both sites, a wide range of productivity levels was available resulting from different long-term fertilisation. In order to identify underlying mechanisms of the species richness–productivity relationship we included the seasonal dynamics and the number of individuals of each species in our analysis. We sampled 10 and 21 plots, respectively, at the two sites in May, June and July by harvesting all aboveground parts of vascular plants in 0.25 m 2 subplots. Species richness, number of individuals of each species and community biomass as a surrogate of productivity were recorded in each sample. At one site, the relationship between species richness and biomass was significantly positive in the May and June harvest. This relationship disappeared in the July harvest due to a reduction in species richness at high productivity levels. The relations between species richness and number of individuals and between number of individuals and biomass paralleled the species richness–productivity relation but the individual number–biomass relationship remained positive until the last harvest. Between-species differences in individual number–community biomass relationships and their seasonal dynamics revealed “interspecific competitive exclusion” even though the species richness–biomass relationships were not negative or hump-shaped. At the second site, species richness was not related to productivity or to number of individuals. Our study demonstrated the importance of temporal dynamics and regional processes in understanding species richness–productivity patterns. Die Beziehung zwischen pflanzlicher Artenvielfalt und Produktivität wurde in einjährigen Brachen an zwei ähnlichen Standorten in Mitteleuropa untersucht. Innerhalb beider Standorte hatte eine langjährig unterschiedliche Düngung zu grossen Differenzen in der Produktivität geführt. Um die der Artenvielfalt-Produktivitäts Beziehung zugrundeliegenden Mechanismen heraus zu arbeiten, wurden die zeitliche Dynamik und die Individuenzahl jeder einzelnen Art in die Analyse einbezogen. Im Mai, Juni und Juli wurden an beiden Standorten die oberirdischen Teile aller Gefässpflanzen in 10 bzw. 21 Teilflächen von je 0.25 m 2 abgeerntet. Für jede Probe wurden die Artenzahl, die Individuenzahl pro Art sowie die Biomasse als Maß für die Produktivität bestimmt. An einem der beiden Standor