The interrelationship between productivity, plant species richness and livestock diet: a question of scale?

Abstract

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 m 2 ) and for two years at a broad scale (79 m 2 ). 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 ʻhumpʼ 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 (2 m 2 ), 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.

Shifts in plant community structure of a threatened sandy grassland over a 9‐yr period under experimentally induced nutrient regimes: is there a lag phase?

“…These findings can explain the significant influence of the main effect ‘year’ throughout all investigated variables, and also that precipitation strongly impacts development of the vegetation, which is consistent with experiments of Süss et al. () at the same site. However, plots with high‐dose N showed a decrease in species number after a lag phase of about 5 yr, and phytodiversity was about five species (20%) lower than on plots without higher‐dose N.…”

“…A negative relationship between plant species richness and productivity for early and mid‐successional stages of nutrient‐poor sand grasslands was detected by Süss et al. () and, therefore, sandy pioneer grassland with a high species diversity can change into vegetation with only a few competitive species following fertilization. We detected that the species number as well as the cover of threatened species was reduced.…”