Bayreuther Institut für Terrestrische Ökosystemforschung
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Aphids on Norway spruce and their potential role for C and N-fluxes in forest ecosystems


From 01/1995 to 12/1997

Principal Investigator: Bernhard Stadler
Staff: Beate Michalzik
Grant: 0339476 B Vorhersage und Erklärung des Verhaltens und der Belastbarkeit von Ökosystemen unter veränderten Umweltbedingungen

Biogeochemical studies on ecosystem processes typically ignore herbivores because of the difficulty of measuring and manipulating their abundance, distribution or life histories and assessing their effects. Aphids, however, are rather easy to rear on their host plants and they are known to be able to severely affect the growth performance of their host plants. In many cases they excrete large amounts of honeydew, an easy available sugar source, which could affect the distribution and abundance of honeydew consumers, such as micro-organisms or ants, which in turn are likely to affect the flow of nutrients through an ecosystem. The study on the effect of aphids on ecosystem processes had two major objectives: a) to demonstrate that aphids are a significant source for the spatial heterogeneity and temporal variability in flows of nutrients within a forest ecosystem and b) identifying the type of information which is important or redundant at the individual or population level when ecosystems are investigated. The methods used to investigate these questions embrace laboratory and field experiments on different scales. E.g. at the level of individuals, plant quality and temperature had the most important effects on the reproductive biology of Cinarids and on honeydew production. However, their combined effects on aphid fitness are not straightforward. At the level of populations, predator-prey relationships and aphid-ant relationships were key mechanisms affecting the population dynamics of aphids. The abundance of Cinarids on Norway spruce was linked to the population dynamics of micro-organisms in the phyllosphere via honeydew. At the level of the ecosystem the path of honeydew and associated metabolites (e.g. DOC, DON, NO3-N, NH4-N) was followed in throughfall and forest floor leachates in a Norway spruce stand and in a simulation experiment. We were able to demonstrate that aphids significantly affect above and below ground carbon and nitrogen cycling. Linking the ecology of aphids and micro-organisms with the biogeochemistry of ecosystems is likely to promote the understanding of the behaviour of coniferous ecosystems.

List of publications of this Project

Stadler, B; Michalzik, B: Effects of phytophagous insects on micro-organisms and throughfall chemistry in forested ecosystems: herbivores as switches for the nutrient dynamics in the canopy., Basic and Applied Ecology, 1, 109-116 (2000) -- Details
Michalzik, B; Stadler, B: Effects of phytophagous insects on soil solution chemistry: herbivores as switches for the nutrient dynamics in the soil., Basic and Applied Ecology, 1, 117-123 (2000) -- Details
Michalzik, B; Müller, T; Stadler, B: Aphids on Norway spruce and their effects on forest floor solution chemistry, Forest Ecology and Management, 118, 1-10 (1999) -- Details
Stadler, B; Dixon, AFG: Ant attendance in aphids: why different degrees of myrmecophily?, Ecological Entomology, 24, 363-369 (1999) -- Details
Stadler, B; Michalzik, B: The impact of spruce aphids on nutrient flows in the canopy of Norway spruce, Agricultural and Forest Entomology, 1, 3-9 (1999) -- Details
Stadler, B; Michalzik, B; Müller, T: Linking aphid ecology with nutrient fluxes in a coniferous forest, Ecology, 79(5), 1514-1525 (1998) -- Details
Stadler, B; Michalzik, B: Linking aphid honeydew, throughfall, and forest floor solution chemistry of Norway spruce, Ecology Letters, 1, 13-16 (1998) -- Details
Stadler, B; Michalzik, B: Aphid infested Norway spruce are "hot spots" in throughfall carbon chemistry in coniferous forests, Canadian Journal of Forest Research, 28, 1717-1722 (1998) -- Details
Stadler, B: The effect of plant quality and temperature on fitness of Cinara pruinosa (Hartig) on Norway spruce, European Journal of Entomology, 95, 351-358 (1998) -- Details
Stadler, B: Egg distribution and survival of Cinara pilicornis (Hartig) on damaged and undamaged Norway spruce (Picea abies) (L.) Karst., Journal of Applied Entomology, 121, 71-75 (1997) -- Details
Stadler, B: The relative importance of host plants, natural enemies and ants in the evolution of life-history characters in aphids in Beck E., Bendix J, Kottke I, Makeschin F, Mosandl R,: Ecological Studies, Springer Verlag, 130, 241-256 (1997)
Stadler, B; Müller, T: Aphid honeydew and its effect on the phyllosphere microflora of Picea abies (L.) Karst., Oecologia, 108, 771-776 (1996) -- Details
Stadler, B: Adaptive allocation of resources and life-history trade-offs in aphids relative to plant quality, Oecologia, 102, 246-254 (1995) -- Details
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