Fluctuations in population numbers, abundance, or density from one time step to the next are the norm. Population cycles make up a special type of population fluctuation, and the growth curves in population cycles are marked by distinct amplitudes and periods that set them apart from other population fluctuations. In the animal kingdom, it may be explained that this fluctuation is the result of a change in the food chain and the density of consumers' arrangement, which over the years entails increases and decreases in the size of the population. But the situation is different in the plant kingdom: the plant may be lost and disappear for a long time in one region, and then it will return strongly and disappear in another region and so on. Some may explain this by the presence of seeds in the soil, which allow the plant to return from the dark. The reason for its disappearance may be natural as a result of climate change or the destruction of environments and others. Generally, this fluctuation is normal, but when is the matter dangerous, worrying and warranting intervention? How can we expect that the plant will return after its disappearance in a region?
in my work on IUCN Red List Assessments for endemic plants I recorded these fluctations
Research Primula boveana IUCN Red List
Research Rosa arabica - IUCN Red List
Research Phlomis aurea IUCN Red List
Research Anarrhinum pubescens IUCN Red List
All these species listed as threatened species
Could the fluctations an indicator?
It's hard to say without long-term data if biologists can have any idea if long periods of dormancy are normal. Some species respond to certain disturbances (fire, tree-falls, herbivory) with growth, flowering, or recruitment. Whereas others (usually dominant species) are affected negatively. Orchids are notorious for random periods of dormancy; some periods are difficult to explain with environmental factors. I would say we need more long-term population trend data before we can assume whether fluctuations can threaten long-term persistence or population viability.
Dear Scott G. Ward
I strongly agree with you that tracking the population size at close intervals and for a long period of time may give an indication of the condition expected in the future. Acctually I find this is very difficult, especially in endemic species of little geographic range, which have small numbers of mature individuals.
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