forest survey release 21 

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This report is from the Division of Forest Economics 

Russell N. Cunningham, Chief 

CENTRAL STATES FOREST EXPERIMENT STATION 

U, S. DEPT. OF AGRICULTURE, FOREST SERVICE 

111 Old Federal Building, Columbus, Ohio 

W. G. McGinnies, Director 
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Frontispiece.--Forest Survey regions in Iowa. 
The recent Forest Survey of Iowa reported as for~~t land only those areas 

larger than 1 acre in size and more than 120 feet wide.~ In farming states like 

Iowa, however• such small patches and narrow strips of wooded land take on greater 

significance than in more heavily forested states. Reasons for this are that 

small woodlands~ especially in the form of narrow strips~ affect the use of adjacent land by providing game cover and protection from wind as well as forest products for local use. 

Had roadside and streamside strips and shelterbelt plantings on small 

areas been included in the Forest Survey, Iowa 8 s recorded forest area would have 

been increased by 25 percent. So, in order to get a better idea how much timber 

is contained in these narrow strips, a special study was made of them. By using 

aerial photographs much information was obtained at very little additional cost 

to the Forest Survey. The results of this study are reported here in terms of 

the three major forest regions of the State (frontispiece). 

Photo estimates alone of course cannot provide firm estimates of timber 

volume or timber cut on small strips. So when resurveys are begun, it may be 

advisable to include ground measurements on narrow strips in Iowa in order to 

get a more complete picture of the timber situation. 

lJ Central States Forest Experiment Station. Iowa Forest Statistics. 

Forest Survey Release 20, 58 pp., illus. 1956. 
There are 664 1 000 acres of "forest" 

in narrow natural or planted strips in 

Iowa (table 1). This area is in addition 

to the 2 1 620 1 000 acres of commercial 

forest_~and as defined by the Forest 

Survey~. 

The lowest percentage of land in 

strips is in the western region, and the 

highest percentage is in the southeast. 

The western region, however, leads in 

total acreage in strips, whereas the 

northeastern area is a poor third. 

~ Ibid., page 53. 

Figure 1.--A natural forest strip borderL~g a stream. 
For the State as a whole, nearly 

two-thirds of the area in strips is 

natural forest; a little over one-third 

has been planted. However, 52 percent 

of the strips in the western region are 

planted, whereas planted strips in the 

other two regions average only 23 percent of the total strip area. This 

should be expected because the western 

region is primarily prairie. 

The natural strips are stringers 

along stream and drainage courses--

remains of larger forest areas and small, 

natural farm woodlots or isolated clumps 

of forest growth (fig. 1). Planted 

strips are narrow (less than 120 feet 

wide) shelterbelts, fence rows, or windbreaks, 9r are planted farm woodlots 

less than 1 acre in size. Orchards and 

ornamental or shade trees on a farmstead 

are not considered as either forest land 

or narrow strips. 

Table 1.--Area in narrow strips 

All strips Natural strips Planted strips 

Region :Thousand: Percent of :Thousand: Percent of :Thousand: Percent of 

acres land area acres land area acres land area 

Northeastern 156 2.0 118 1.5 38 0.5 

Southeastern 244 2.8 190 2.2 54 .6 

Western 264 1.3 126 .6 138 .7 

State 664 1.9 434 1.2 230 0.7 

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About 40 percent of the acreage in 

strips is in sawtimber stands with a minimum 

net volume per acre of 1,500 board-feet 

(International 1/4-inch rule) in sawtimber 

trees (fig . 2) . More than half is in poletimber stands (table 2). These are stands 

which do not qualify as sawtimber but are 

at least 10 percent stocked with trees 5 

inches d.b.h. and larger. The remaining 

6 percent of the acreage is in seedling 

and sapling stands (predominantly trees 

less than 5 inches d.b.h,) • 

Figure 2.--A forested strip containing sawtimber. 
The foregoing percentages are 

about the same for both natural and 

planted strips, but there is some variation by region. In the northeastern 

region slightly more of the naturalstrip acreage is in sawtimber 1 and in 

the southeast two-thirds of the plantedstrip acreage is in poletimber. 

The relatively high occurrence 

of sawtimber stands in natural strips 

in the northeast is probably because 

part of the original forest cover has 

been retained on areas obviously unsuited for farming. On the other hand, 

the much higner percentage of poletimber stands in the southeastern plantations indicates either a later planting program or a faster rate of sawtimber 

cut. 

Table 2.--Stand-size class of narrow strips 

(In percent) 

Region 

Northeastern 

Southeastern 

Western 

State 

Total Natural Planted 

Saw- :Pole- :Seedlings Saw- :Pole- :Seedlings Saw- :Pole- :Seedlings 

:timber:timber:~ saplings:timber timber:~ saplings:timber:timber:& saplings 

46 46 8 47 43 10 45 55 0 

37 56 7 38 53 9 29 67 4 

39 57 4 35 57 8 42 57 1 

40 54 6 40 51 9 40 59 1 

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A little more than one-fifth of 

all the area in strips has good stocking, 

that is at least 70 percent of the area 

of each stand is covered by the crowns 

of trees belonging to the assigned standsize class and all larger stand-size 

classes. The remaining four-fifths is 

almost equally divided between fair (40 

to 70 percent crown coverage) and poor 

(less than 40 percent coverage) stocking 

(fig. 3 and t able 3) . 

Figure 3.--Much of the area in strips is too 

poorly stocked to produce good timber. 
The same general distribution 

holds for both natural and planted 

strips except that good stocking is 

found on 18 percent of the natural 

strips and 29 percent of the planted 

strips. Although there are some regional variations, there is more poorly 

stocked area than either fair or good. 

Table 3. -Stocking of narrow strips 

(In percent) 

Total Natural Planted 

Region Good Fair Poor: Good Fair Poor: Good Fair Poor 

Northeastern 23 40 37 20 43 37 32 32 36 

Southeastern 18 37 45 17 40 43 20 28 52 

Western 24 37 39 17 35 48 31 38 31 

State 21 38 41 18 39 43 29 35 36 

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About one-fourth of I owars stri pforest area is located on bottomland, 

including stream borders, low benches 

and coves, and old riverbeds (fig, 4 and 

table 4), The remainder is divided equally between the level upland and r ough 

upland sites. Level upland i s level or 

gently rolling topography without prominent 

drainage patterns, and is land likely to 

remain as pasture or cropland if cleared. 

Rough upland is rugged t opography with 

sharp drainage patterns, and will probably 

revert t o forest or wasteland if cleared. 

Figure 4 .--Forest ed strips along drainages and on 

level upland (backgrow,d). 
More than half the area in natural strips is on rough upland sites. 

On the other hand, 85 percent of the 

strip or windbreak planting is confined 

to level uplands. Such land is generally more valuable for agriculture 

and more subject to wind damage, and hence 

more in need of protection. The only 

marked regional difference is in the 

western region where nearly half of the 

natural-strip acreage is found on 

bottomland sites. 

Table 4.--Topographic site of narrow strips 

(In percent) 

Total Natural Planted 

Region :Level :Rough :Bottom-:Level :Rough :Bottom-:Level :Rough :Bottom-

:upland:upland: land :upland:upland: land :upland:upland : land 

Northeastern 32 41 27 13 52 35 89 8 3 

Southeastern 26 50 24 12 59 29 76 20 4 

Western 49 24 27 6 45 49 89 4 7 

State 37 37 26 10 53 37 85 9 6 

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A narrow strip may serve as a 

windbr e ak or a combination she lterbe lt 

and fence row, or it may be merely part 

of a natural forest . A windbreak is 

planted for the protection of farmsteads 

and farm buildings (fig,5), but a shelterbelt or fence row is generally used for 

the protection of fields and roads. Natural strips may or may not serve a purpose 

other than producing timber. 

Figure 5.--A strip of trees serving as a farm windbreak. 
In Iowa about half of all the 

area in strips is contiguous with 

larger forest areas; one-quarter is 

in windbreaks and one-quarter is in 

shelterbelts or fence rows (table 5) . 

More than 70 percent of the naturalstr ip area is part of larger forests. 

Two-thirds of all the plantedstrip area is in windbreaks. In the 

southeastern region , more than 70 percent is in shelterbelts or fence rows 

but in the western region more than 

80 percent is in windbreaks. 

Since the southeastern region has 

the great est area of easily erodable 

soil, it would seem that shelterbelts 

would be more common there so that fields 

and roads might be protected. Actually , 

however, the plant ings in the southeast 

are largely fence rows. This is also 

true in the southern half of the State 

where Osage-orange was planted for fencing purposes. The earlier settlers were 

primarily interested in fences and only 

slightly interested in shelterbelts. But 

in the western prairie area, farmsteads 

require greater protection from wind and 

hence more windbreaks are used. 

Table 5.--Special use of narrow strips 

(In percent) 

Total Natural Planted 

Shelter-: Shelter-: Shelter-: 

Region Wind- belt or : Rem- Wind- belt or : Rem- Wind- belt or : Rembreak :fence row: nant break :fence row: nant break :fence row: nant 

Northeastern 17 27 56 3 23 74 61 39 0 

Southeastern 9 41 50 4 31 65 26 74 0 

Western 48 11 41 10 5 85 83 17 0 

State 26 26 48 6 21 73 66 34 0 

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Three-fifths of the area in natural strips is contained in units less 

than 1 acre in size and 97 percent in 

units smaller than 15 acres (table 6). 

In the planted strips, four-fifths of 

the windbreak area and three-fourths of 

the shelterbelt area occur in units 

smaller than 1 acre, and, nearly all of 

the area in both types of planting is 

in units less than 5 acres in size. 

There is little regional variation in 

the average size of strips. 

Figure 6.--Many of the forested strips are long, 

narrow stringers. 
Inasmuch as a narrow strip by 

definition is less than 120 feet wide 

or smaller than 1 acre, a natural 

strip larger than an acre would be a 

long, narrow stringer. So it is not 

unreasonable that as much as 40 percent of the natural strips are larger 

Table 6.--Average 

(Percent in 

size 

than 1 acre, because the stringer shape 

is characteristic of many such strips 

(fig. 6). Plantations for farmstead and 

field protection are usually much smaller 

in area since the plantings are restricted to windbreaks and shelterbelts which 

will result in direct benefits. 

of narrow strips 

range of acres) 

Size of natural strips (acres) Size of planted strips (acres) 

Windbreak Shelterbelt 

Region 0- 1- 5- 15- 40- o- 1- 5- o- 1- 5-

0.9 4 14 39 119 :120+ 0.9 4 14 0.9 4 14 

Northeastern 53 34 11 1 0 1 82 11 7 82 12 6 

Southeastern 60 35 3 2 0 0 82 18 0 76 20 4 

Western 67 25 3 4 0 1 80 19 1 73 24 0 

State 60 31 6 2 0 1 81 17 2 76 20 3 

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More than 4 out of every 5 Iowa 

farms have either planted or natural 

windbreaks (fig . 7) . This is especially surpri sing when it is considered that windbreaks comprise only half 

of l percent of the State's total land 

area. 

As might be expected, the western 

region has the highest percentage (92) 

of farms with windbreaks while the southeast has the lowest. This distribution 

among the various regions is similar to 

that shown in table 6. 

Figure 7.--A farm home well protected by trees. 
Farmers do obtain some wood 

products, such as fence posts, fuelwood, and occasional sawlogs and veneer 

bolts, from strips of timber that have 

been left or planted. But these are 

primarily salvage products obtained by 

removing dead or damaged trees, especially from planted strips that were 

established for protection of buildings, 

livestock, roads, and fields. In 

addition to the protection provided, 

the trees make the farm home and surroundings more attractive and livable. 

They also provide shelter for birds 

and wildlife which bring enjoyment to 

local residents in many ways. 

Normally "forest" trees are 

evaluated in terms of wood products; 

these intangible values have seldom 

been estimated. There is no doubt, 

however, that the farmer values his 

strips of timber greatly when he allows 

them to occupy highly productive cropland. It appears that trees are especially valued where natural stands are 

sparse, as evidenced by the greater 

area of strip plantations in western 

Iowa than in the remainder of the 

State. 

Agriculture - Forest Service - Columbus, Ohio 

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