People aren't the only things that age. South Dakota windbreaks and shelterbelts, planted in the 1920's and 1930's are showing their age too. Today, mature trees occupy 71 percent of the timberland area in the state. In eastern South Dakota many of those stands were planted as windbreaks. North Central Research Station scientist Earl Leatherberry stated, "without replanting or renovation these windbreaks will break apart and the risk to agriculture from wind damage will increase."
In addition, severe weather such as the ice storms, record snowfall, and blizzard conditions of 1996-1997 also take their toll on tree plantings. In 1997, forester Gregory Josten, from the South Dakota Resource Conservation and Forestry Division, surveyed 45 windbreaks to assess damages. Josten said, "87 percent of the surveyed windbreaks needed renovation and District foresters or conservationists can assist landowners considering renovation of existing shelterbelts."
Not only are the forests that were planted to prevent wind damage aging, but the riparian forests, next to the waters edge, are also maturing. Early in the 1800's there were extensive stands of cottonwood in South Dakota. Since 1935, cottonwood has declined from 94 thousand acres to 36 thousand acres. A typical cottonwood tree lives to be 75 years old before it starts to decline and eventually dies. Leatherberry explained, "the reason cottonwood trees are succumbing to old age is because they grow best in sandy soils and open sunlight on floodplains. Flood control projects either permanently inundate cottonwood habitat or eliminate the seasonal floods which provide the sandy soils cottonwoods thrive on."
These riparian forests intercept many or the nutrients generated by agricultural practices. Research has shown that well-developed forested riparian areas, from 90 to 150 feet wide, reduce nitrogen in ground water by 50 to 100 percent and surface runoff from 78 to 98 percent.
For further information on South Dakota's forest resource ask for a copy of Research Paper NC-338, South Dakota's Forest Resources Outside the Black Hills National Forest, 1996 by Leatherberry, Piva and Josten.
The publication is a cooperative effort of the USDA Forest Service, North Central Research Station in partnership with the South Dakota Department of Agriculture, Resource Conservation and Forestry Division. Copies may be ordered through: State Forester South Dakota Department of Agriculture Resource Conservation and Forestry Division 523 East Capitol Avenue Pierre, South Dakota 57501-3182 Phone: 605-773-3623 Fax: 605-773-4003
Earl Leatherberry may be reached at 651-649-5138 or email at eleatherberry@fs.fed.us. Greg Josten may be reached at 605-394-2395 or email at greg.josten@state.sd.us.