Population dynamics of a host-specific root-feeding cyst nematode and resource quantity in the root zone of a clonal grass

Recent studies have suggested that root-feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding-specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and greenhou...

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Bibliographic Details
Published in:	Oikos 2006-03, Vol.112 (3), p.651-659
Main Authors:	Van der Stoel, C. D., Duyts, H., Van der Putten, W. H.
Format:	Article
Language:	eng
Subjects:	Ammophila arenaria Animal and plant ecology Animal, plant and microbial ecology Biological and medical sciences bottom-up Cyst nematodes Cysts Ecosystems Eggs Flowers & plants food-web Fundamental and applied biological sciences. Psychology General aspects Grasses Heterodera arenaria heterodera-avenae insect herbivory Invertebrates mycorrhizal fungi Nemathelminthia. Plathelmintha Nematoda Nematodes Plant roots plant-parasitic nematodes Plants relative roles Rhizosphere Root biomass soil Soil nematodes top-down Worms Young animals
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Summary:	Recent studies have suggested that root-feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding-specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and greenhouse studies pointed at bottom-up control by their host plant. Here we examine the population dynamics of H. arenaria in the field in relation to resource quantity in the root zone of Ammophila arenaria (marram grass). Ammophila arenaria is a pioneer grass in mobile coastal foredunes of northwestern and Mediterranean Europe. Every year, the plant expands clonally into freshly deposited layers of wind-blown sand, followed by dispersal and build-up of the nematode population into the new root zone. In a newly developing root zone the first H. arenaria cysts were observed one month after the first new roots were detected, indicating that nematode dispersal is not limiting the initial establishment of new populations. Throughout the growth season, the numbers of cysts, as well as the numbers of eggs and juveniles within cysts, were related to the quantity of roots. However, cyst density varied between years. Therefore, we conclude that in new root layers of A. arenaria cyst nematodes are bottom-up controlled by resource quantity, but that other factors, for example resource quality, influence the relation between nematode abundance and resource quantity. In deeper root zones the nematode abundance declines over time. Here, numbers of cysts were not related to root biomass, while numbers of eggs and juveniles inside the cysts were weakly related. This points at other factors than resource quantity, for example the quality of the roots or unsuitable abiotic environmental conditions that have a stronger influence on cyst numbers than resource quantity. We discuss how bottom-up control of cyst nematodes may indirectly protect the plant against harmful root knot nematodes.
ISSN:	0030-1299 1600-0706