Juniperus Virginiana - Ecology

Ecology

It is a pioneer invader, which means that it is one of the first trees to repopulate cleared, eroded, or otherwise damaged land. It is unusually long lived among pioneer species, with the potential to live over 850 years. The tree is commonly found in prairies or oak barrens, old pastures, or limestone hills, often along highways and near recent construction sites. It is an alternate host for cedar-apple rust disease, an economically important disease of apples, and some management strategies recommend the removal of J. virginiana near apple orchards

In many areas the trees are considered an invasive species, even if native. The fire intolerant J. virginiana was previously controlled by periodic wildfires. Low branches near the ground burn and provide a ladder that allows fire to engulf the whole tree. Grasses recover quickly from low severity fires that are characteristic of prairies that kept the trees at bay. With the urbanization of prairies, the fires have been stopped with roads, plowed fields, and other fire breaks, allowing J. virginiana and other trees to invade. Trees are destructive to grasslands if left unchecked, and are actively being eliminated by cutting and prescribed burning. The trees also burn very readily, and dense populations were blamed for the rapid spread of wildfires in drought stricken Oklahoma and Texas in 2005 and 2006.

Junipers also benefit from the increased CO₂ levels unlike the grasses with which they compete. Many grasses are C4 plants that concentrate CO₂ levels in their bundle sheaths to increase the efficiency of RuBisCO, the enzyme responsible for photosynthesis. Junipers are C3 plants that rely on the natural CO₂ concentrations of the environment, and are less efficient at fixing CO₂. However, the trees will benefit from increased CO₂ levels, unlike grasses.

Damage done by J. virginiana includes outcompeting forage species in pastureland. The low branches and wide base occupy a significant portion of land area. The thick foliage blocks out most light, so few plants can live under the canopy. The needles that fall raise the pH of the soil, making it alkaline, which holds nutrients such as phosphorus, making it harder for plants to absorb them. Juniperus virginiana has been shown to remove nitrogen from the soil after invading prairie. It has also been found to reduce carbon stores in the soil. This reduction in soil nutrients also reduces the amount and diversity of microbial activity in the soil.

Cedar waxwings are fond of the berries of these junipers. It takes about 12 minutes for their seeds to pass through the birds' guts, and seeds that have been consumed by this bird have levels of germination roughly three times higher than those of seeds the birds did not eat. Many other birds (from bluebirds to turkeys) and many mammals also enjoy these berries.