Question: What relationship exists between productivity, plant species richness and livestock diet? Are the results dependent on scale?
Location: A sheep-grazed Koelerio-Corynephoretea sandy habitat of the northern upper Rhine (Germany) as a low productivity model system.
Methods: The investigation was carried out for three years at a fine scale (2 m2) and for two years at a broad scale (79 m2). Productivity was measured by means of weighed above-ground phytomass for fine scale and colour-infrared (CIR) aerial photographs of the same system for fine and broad scales. For both scales, total numbers of vascular plant species and numbers of endangered vascular plant species were extracted from current vegetation relevés. Additionally, we obtained data on livestock diet (grazed phytomass, crude protein content).
Results: Statistical analyses show an influence of the year on all variables; relationships between variables are not significant in every year. Species richness and number of endangered species are negatively related to productivity at fine scale while crude protein content and grazed phytomass are positively related to productivity. At the broad scale the diversity-productivity relationship shows a 'hump' with highest species numbers in middle pioneer stages; numbers of endangered species are highest in all pioneer stages.
Conclusions: We found a strong impact of scale and year on the diversity-productivity relationship. It is inappropriate to analyse only small plots (2m2), and it is necessary to study different years. This vegetation complex is dependent on grazing impact; thus there is an inversely proportional relationship between nature conservation value (high diversity) and livestock nutrition.
Nomenclature: Wisskirchen & Haeupler (1998).