Final answer:
The hypothesis that additional species contribute little to community function after a certain level of species richness is partially true and subject to scientific investigation in community ecology.
Step-by-step explanation:
The question poses a hypothesis that there is a threshold in species richness after which additional species have minimal impact on community function. This concept is a matter of ongoing scientific debate and research within the field of community ecology. Empirical evidence suggests that while greater species richness generally contributes positively to ecosystem functions such as productivity, nutrient cycling, and resilience, there may indeed be diminishing returns after a certain point. However, this relationship can be complex and context-dependent, influenced by factors such as ecosystem type, the types of species, and their functional roles within the community. Given the variations in scientific findings, the hypothesis in question may be considered partially true and yet still be a subject of research and discussion among ecologists.