Final answer:
The decline in population density coupled with an increase in biomass among surviving individuals is referred to as self-thinning, which is a natural result of density-dependent factors within ecological populations.
Step-by-step explanation:
The progressive decline in density and increase in biomass of remaining individuals in a population is known as self-thinning. This process typically occurs in populations where resources such as light, water, and nutrients are limited, and as a result, only the strongest individuals survive, while the rest perish or fail to thrive. Self-thinning is a natural consequence of density-dependent factors such as competition for resources, which tend to increase mortality or reduce reproductive success as a population approaches its carrying capacity.
Density-dependent regulation is critical in understanding the dynamics of ecological populations. As the population density increases, the competition among individuals for limited resources also increases, leading to a higher mortality rate. In cases where these density-dependent pressures become too great, population size may decrease, subsequently decreasing the competitive pressure, which allows for an increase in individual growth and a subsequent rise in biomass per surviving individual.