One can think of different ways that biodiversity can be regulated in the framework of food-webs or more generally networks of interactions:
Top-down: the effect of predation, hervibory, parasitism
Botton-up: food/nutrients
Disturbance:
In a more microscopic way could also have stabilizing influence or not
Trophic interactions
Competitive or negative interactions
Mutualistic or positive interactions
No interactions (Neutral)