Thursday, August 9, 2007 - 2:10 PM

OOS 43-3: Unique or important systems I - Mixing litter of plants with different nitrogen economies: Hemiparasites in the sub-Arctic

Helen Quested, Stockholm University

Plant groups with particular suites of traits potentially play a key role in determining community structure and ecosystem processes. An example is the root hemiparasitic plants of the Orobanchaceae (ex-Scrophulariaceae), which are abundant in many nutrient-poor alpine and (sub-)Arctic ecosystems. Their abundance is likely to change in response to global change factors, providing a wider relevance for their study. It is well established that their unique mode of nutrition (deriving nutrients, water and some carbon from their host via root connections) has potential negative consequences for their host plant(s), with subsequent impacts on community structure and dynamics. However, the consequences of having access to an alternative nutrient source for leaf and litter traits, and subsequent impacts on nutrient cycling, remain under-studied. Nutrient-rich hemiparasite litter may influence nutrient dynamics both directly, and indirectly by stimulating the decomposition of other (nutrient-poor) species’ litters. Focussing on sub-arctic heath vegetation the Abisko area, Sweden (68o 21’ N, 18o 49’ E), it is shown that leaf litter of the common hemiparasite Bartsia alpina lost c. 18 times more nitrogen than litter of dwarf shrubs over 2 years of field decomposition, and stimulated the growth of commonly co-occurring plant species. Somewhat surprisingly, hemiparasite litter had both positive and negative effects on the decomposition of other species’ litter; the strength and direction of non-additive effects were found to vary over time and between different decomposition environments. This clearly demonstrates the importance of the ecological context, rather than species-specific litter quality alone, in determining interactions between litters in mixture. Some potential mechanisms underlying the variation in observed non-additive interactions are discussed.

See more of OOS 43 - Biodiversity in the litter layer: Mechanisms and applications
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