Impact of soil nematodes on salt-marsh plants: a pilot experiment

We tested whether the removal of nematodes by means of nematicide applicati on changed plant performance or influenced plant competition. The study inv olved the two common plant species Artemisia maritima and Festuca rubra gro wing in intact sods collected from a temperate salt marsh. Half of the sods were treated with fenamiphos ('Nemacure', Payer AG), a nematicide controll ing both endo- and ectoparasitic nematodes. In untreated soil, the number o f both total and plant-parasitic nematodes (7000 vs. 1000 per 100g fresh so il, respectively) was comparable to accounts from other salt marsh systems. After four months, the nematicide had reduced nematode numbers by 90%, but no influence on plant biomass or competitive ability of the two plant spec ies was observed. As we did not follow the trajectory of nematicide effects on the nematodes, the exposure period of the test plants to low numbers of nematodes cannot be assessed. Experimental periods may need to be extended in order to evaluate long-term effects of reduced nematode numbers on plan t productivity and plant competition in temperate salt marshes. On the basi s of this pilot experiment we regard plant-parasitic nematodes to have a mi nor direct impact on productivity and interspecific relationship between th e salt-marsh plant species investigated.