Oaks are among the most common hardwood tree species in many parts of Virginia. Because of their importance both as a source of forest regeneration and as a mast crop for wildlife, each year’s acorn crop is the subject of much attention. Many reports from various parts of the Commonwealth indicate that the acorn crop this fall is very light, according to officials at the Virginia Department of Forestry (VDOF) and the Virginia Department of Game and Inland Fisheries (DGIF).
VDOF Research Program Manager Jerre Creighton said, “Acorn production varies widely – from nearly zero to a quarter million or more acorns per acre. Different locations, years, species and even individual trees produce extremely different crops, and heavy ‘bumper’ crops occur only every two to seven years.”
Many factors – such as weather, insects and disease – that collectively influence acorn development from the time of flower initiation to acorn maturity.
Late spring freezes and high humidity during pollination are primary causes (we experienced both of these over much of Virginia in 2013). In addition, research has shown that the inherent cycles between bumper crops and light crops may be an adaptation to allow the trees to restore their resources following a bumper crop.
Creighton said, “In other words, a large crop one year may reduce the trees’ resources resulting in lower production the following year(s). Since 2012 was a bumper crop of acorns for much of Virginia, this could be another explanation for this year’s light crop. The overall consensus seems to be that there are inherent cycles of reproduction that are modified by the impact of weather conditions in a particular location.”
Gary Norman of DGIF said, “Acorn production in Virginia in 2013 was low – comparable to the previous low in 2008. The white oak crop appeared to uniformly fail across the state, while some pockets (generally in eastern Virginia) of good red oak production were found. Mast production has alternated from high to low levels since 2010. The impacts of acorns on wildlife populations are extensive and complex. And they are most dramatic where there is little diversity of habitat types and few alternative food sources to acorns.”
DGIF officials are concerned about a light crop because acorns are a preferred food for many wildlife species, including white-tailed deer, black bear and wild turkey. Acorns are rich in fat, soluble carbohydrates and energy, which are important nutritional needs that contribute to the animal’s body condition, survival, harvest rates, reproduction and, eventually, population status. The roaming range of black bear and wild turkey can increase two- to four-fold in years with mast failures, and long-range gray squirrel movement can be significant as they search for acorns.
Norman said, “Oftentimes the search for food creates situations that bring wildlife closer into residential areas to find human-related food sources resulting in unwanted interactions between animals and people.”
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