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To date the shelterbelt project has worked on sites in Iowa, Nebraska, and Indiana. Beginning in 2000, sites will be studied in Wisconsin and Minnesota.
 
 

Highway Farms Site, Boone Co. Iowa

Figure 1. (left) Highway Farms field windbreak composed of one row each of shrubs, silver maple and hybrid poplars. J. Tyndall.
 

This 3 row field shelterbelt, planted in 1994, is composed of one row of poplar trees (Carolina poplar 'Eugenei'), one row of silver maple (Acer saccharinum) and a third row of assorted small shrubs: ninebark (Physocarpus spp.), highbush cranberry (Viburnum spp.) and dogwood (Cornus spp.). The shelterbelt is planted in an ‘L’ shape with the long axis running in an East-West direction for 2450 feet (750 meters) and the shorter, North-South axis for 1000 feet (300 meters). The rows are oriented with the shrubs to the predominant windward side, followed by the maples and the poplars on the leeward side. Spacing is 11 feet (3.2m) between rows and 5 feet (1.3m) between trees. Soil types in the area are Clarion (fine-loamy, mixed, mesic typic Hapludoll) and Canisteo (fine-loamy, mixed (calcereous) mesic typic Haplaquoll). Management of the windbreak has consisted primarily of weed control and mowing in the early years. In recent years an attempt has been made to prune selected maples in order to promote single stem forms with the eventual objective of removing up to 50% of the maples.

The farm currently manages alternating crops of soybean and corn. The site has a long history of manure applications from a turkey production facility (40 years). Overall growth in the shelterbelt is good, survival in the maples is in excess of 95%, shrubs 50% and poplars 75%. In 1999, the condition of the shelterbelt was fair. Average height growth was 30 feet for the poplars, 25 feet for the maples and 5 feet for the shrubs.

To date, studies at this site include tree growth and structural development monitoring, static pressure flow-field monitoring, cross-field microclimate monitoring, full season weather station monitoring, and crop production measurements.
 
 

Morgan Farm Site, Boone Co. Iowa

Figure 2 (left). Between the rows of a hybrid poplar windbreak on the Morgan Farm Site. G. Horvath.
 

This five row shelterbelt was planted in 1992 and is composed of 4 rows of hybrid poplars (Carolina poplar 'Eugenei') and one row of mixed shrubs (dogwoods and ninebark). The original shelterbelt was planted in an "L’ shape with the long axis running North-South for 1250 feet (375m) and East-West for 500 feet (150m). During the 1993 spring floods most of the East-West leg of the shelterbelt died, while today the North-South shelterbelt established on higher ground remains. Rows were established 10 feet apart with an in row spacing of 4 feet. The trees were seeded underneath with perennial rye grass, which has been periodically moved. Many shrubs and trees are seeding in under the poplars including mulberry, raspberry and the occasional juniper.

Through 1999 the survival and condition of the trees was good, although ???? canker is starting to become visible throughout the shelterbelt. Soil types in the area are Clarion (fine-loamy, mixed, mesic typic Hapludoll) and Canisteo (fine-loamy, mixed (calcereous) mesic typic Haplaquoll).

The trees in 1999 were 32 feet tall. Almost all of the poplars have lost their lower branches up to a height of 6 to 7 feet (2m), creating a rather ‘open’ lower half for the shelterbelt. In the winter of 1998 the western most row of poplars was harvested. In the remaining three rows approximately 1/3 of the trees were also harvested in order to provide more space within rows. By the end of the 1999 season the poplars had re-sprouted to an average height of 6 ft. and were beginning to provide a low shelter. The sprouts from the stumps between the three eastern rows are fewer in number and shorter in height; survival is also significantly reduced from that of the open west row. The harvested timber was used on site for firewood.

Figure 3 (left). Poplar stumps re-sprouting one year after harvest in a four row poplar windbreak. At about 2-3 years of age these sprouts will be pruned to single stems. G. Horvath.
 

To date, studies in this shelterbelt include: tree growth and internal shelterbelt structural development, cross-field microclimate monitoring and crop yields in beans, corn and oats. A long-term management prescription for this design of timber/fiber producing shelterbelt is being developed.
 
 

Burvia Younce Farm Site, Wabash Co. Indiana

Figure 4. (left). Shadows extending across a bean crop from a 3 row conifer and one row shrub windbreak in Wabash, Indiana. These long shadows partly illustrate the extent of the influences of windbreaks on neighboring crop fields. G. Horvath.
 

This shelterbelt, established in 1972, consists of 3 rows of mixed conifers and one row of shrubs with a few scattering of hardwoods along its length. The shelterbelt is 3500 feet long running north to south over very flat terrain. The west row is composed of Russian olives (Elaeagnus hortensis) approximately 10 to 15 feet tall in 1997 and spaced about 8 feet apart. The second row is composed of mixed red (Pinus resinosa) and white pines (Pinus strobus). The third and fourth rows are primarily white pines. The red pines are about 20 feet tall, while the whites are about 25 –30 feet tall. Each row is 15 feet apart and the pines are spaced 15 feet apart. Survival in the shrubs is high, providing for a near continuous row. Red pine survival is low, probably less then 50% with the remainder being in relatively poor condition. The white pines represent near continuous rows with about an 80-90% survival. Scattered large hardwoods (survivors are approximately 250 feet apart along the row), elms (Ulmus spp.), oaks (Quercus spp.) and walnuts (Juglans spp.), were established between the olives. A large number of natural occurring cherries (Prunus spp.) have also established within gaps in the shelterbelt.

The soil in the area is composed of fine-silty, mixed, mesic Typic Agriaquolis and fine-silty, mixed, mesic Aeric Ochraqalfs. Cropping in the field has been a rotation of corn and beans.

To date research on this site had involved shelterbelt structural analysis, three full seasons of microclimate monitoring and crop growth and yield monitoring.

The landowner, although retired, has, under his own initiative, established a second multi-row shelterbelt parallel to the older one and about 900 feet to the east.
 
 

Tom Eischen Farm, Kossuth Co. Iowa

Figure 5. (left) Four row, 12 year old snowfence of ash and honeysuckle. Kossuth Co. IA. G. Horvath
 

This shelterbelt was planted in 1989 under the CRP program for the purposes of protecting Highway 9 running West from the Town of Algona. The windbreak on this site is part of a much longer system along highway that runs for 3.5 miles through 4 sections of Kossuth county. This snowfence type windbreak consists of two rows of ash trees (Fraxinus spp.) and two rows of honey suckles. The honey suckles are placed on the north side of the ash (the side away from the highway). The shelterbelt is set parallel and approximately 200 to the north of the highway.

Currently the ash trees average about 20 -22 feet in height. Spacing in the ash trees is 12 feet between rows and 5 feet between the trees. The honeysuckle are spaced 12 feet between rows and 3-4 feet between plants. some of the ash trees still have spaces between the trees, while the shrubs make a solid row. Originally a row of cedars was planted to the north of the shrubs. On this site the cedars have not survived, but on some other stretches the shrubs continue to survive and grow and have attained heights of 20 feet similar to the ash.