They were free to dine in the heart of the grove. Their numbers have multiplied greatly. It will take several years, but the experiment should tell whether the presence of the wolf keeps the elks out of the aspen regeneration areas. In the grand scale of things, the decline of the wolf throughout the West may be only a minor player in the decline of the aspen. Most experts believe the primary reason for the decline is competition with conifers which reach such great heights that they block out the sun from the shade-intolerant aspen.
Many experts believe fire suppression provides the most plausible explanation.
Fire wipes out conifers, as well as aspen, but the aspen has a trump card. Aspen groves are essentially hundreds of trees growing from the same root. Most of the bio mass of the system is below the ground, where it is protected from fire. So when fire moves in, it destroys the growth above the ground, wiping out the conifers as well, but the aspen grove remains healthy below the ground. After the fire, new aspens spring up from the root system, and there aren't any conifers left to block out the sunlight that is so essential for their growth.