Invasive species is always a troublesome subject when it comes to environments. Luckily, in the Taiga, there has been no introductions of invasive species. Theoretically, if we were introduce an invasive species, say Autumn Olive, into the Taiga, it houses the potential to strain the struggle of life for smaller plants in the area. The Autumn Olive, if it could grow in the Taiga, would grow without any natural predators, and diminish the amount of sunlight smaller, native plant species would have received. Hypothetically speaking, if this Autumn had no natural predators, and killed off all other plant species in the Taiga, every single animal species would die. That means no more moose frolicking through the majestic summer Taiga streams.
As in this food web and all other food webs that shall ever be created by people on earth, the main source of energy is the sun. This is thanks to the photosynthetic plants, which feed the primary consumers, which feed the secondary consumers, and so on. If the population of even a single organism were fluctuate, this fragile temple of life will collapse. For example: Say a species, like the Snowshoe Hare, dies off. Now, any animal that preys on this Hare is forced to find food elsewhere, therefore dwindling that species to possible extinction, and eventually leading to their own death. An even greater example of this would be if the Sun died. If that were to happen, absolutely everything and it's mother would die, with the exception of chemosynthetic organisms. Population in its own is a very wobbly subject in the Taiga. Its difficult for any population to grow here seeing that there are limited resources to feed anything. Wolves cannot increase in population without extra prey to feed on. Moose, unfortunately, cannot increase in population unless there is an increase in everything else.