This kind of direct topic interactions can be associated with the direct or indirect trophic interactions. Organisms of the 2nd species use carcasses of organisms of the 1st species as a substratum. Organisms of the 2nd species use products and constructions of organisms of the 1st species as environment. Water weeds in creeks decrease the current speed and this may be favorable or unfavorable for other species. Direct trophic interactions A. Consumer eats the live body of another species.
Consumer eats non-living portions of the body.
B. Consumer eats excretions of the producer. This is transportation of one species by another. This is when organisms of one species use for their construction activity bodies or excretions of carcasses of another species. However, when bark beetles kill a bunch of firs then pines will start growing in this gap. Thus, bark beetles have an indirect topic effect on pine population.