Answer: D) density independent limiting factor.
A limiting factor is the one which has the potential to limit the growth, abundance and distribution of the population of the species in an ecosystem. A limiting factor can be characterized into two types depending upon the density of the population. This includes density- dependent and density-independent factors.
Density- dependent limiting factor causes the change of the population per capita growth with the increase in population density. For example, predation, the large folk of the prey population is likely to attract the predator population.
Density-independent limiting factor results in the change in the per capita growth of the population independent of density of population. The example includes natural disaster.
A tornado is a type of natural disaster, the effect of which will be independent of the density of the tree population of Carolina mountains forests. Therefore, the decrease in the tree population is the result of a density independent limiting factor.