Dear Victorie

the colour of the apos is important. You say orange which more or less would exclude Orbilia rosea which we consider typically with rose apothecia although the name derives from the rose culture colour.

O. luteorubella is then the choice, although the spores are a bit short (did you evaluate spore size?).

Alluvial means that there is a running water? O. luteorubella prefers standing water (ponds etc.), but this is not obligatory.

The two species are hardly separable except using the ITS or LSU marker.

I see you had luteorubella in Ölmütz with also short spores and more pinkish apos.

Zotto

Dear Zotto, 
thank you very much and sorry for late answer.

What do you mean by "evaluating spore size"? It was measured on 42 spores, although I admit that it's be a bit approximate because of the unsharp photos. I could at least photograph rehydrated exsiccate, but unfortunately it's already in the freezer and will stay there for next few months (to get rid of some larvae etc in the wood). 

The locality is Cernovirske slatiniste in Olomouc-Cernovir. You've already seen/determined O. aurantiorubra, Hymenoscyphus aff caudatus (H+) and H. aff imberbis (H-) from there. No running water (except for slightly acidic Fe3+ spring), but several more boggy places, filled with water after rains - this was in one of them. Maybe "riparian" is better word than "aluvial", I'm not very versed in english terminology yet. I found also some Hymenoscyphus(?) on caddisfly (Limnephilidae) cases in the same place, but it didn't survive in fridge. :-/ 

Best regards,
Viktorie

Sorry, I overlooked your spore data below the photo collage.
For the wood you did not indicate if it is angiospermic and what it could be?
A log?

The pinkish apothecia are on another piece of wood?