UPPER DARN PA R. W.MARQUIS DIFE(=TOR 

LABGE-SCALE a IRPB~TQS TES~ED 

IX POREST S~VGY, PROVE UNSATISFACTORY 

Some camera, which takes continuous-strip 

, photos at larb scales. In this camera a ribbon 

of film is passed across a fixed slit at the 

. . Pocal plane; the speed of the film is synchroniaed with the speed of the aircraft. 

R.ecent1~ we had an opportunity to study 

- v%ded the photos for the study. One area had 

beenphotographed in July, the other in December; 

this gave us a chance to compare summer and win- . 

ter photos., The general quality of the photos 

was good for both areas. I 

! i 

i We made tests - on photo scales ranging from 

,1 inch*= 100 Wet to 1-inch = 1,800 feet. photo 

interpreters edned photos of various scales \ 

I 

' 1 

* - . - * a\, 
and estimated timber volune ,. measured tree 

heights and crown diameters, and identified tree 

species. These observations were checked on 

ground plots. -

Unexpectedly, the accuracy of the interpretations from the large-scale photos was not much t 

better than that c*ommonly-obtained from conven- . 

tional, small-scale photography. Further study, 

however, cleared up sore of our puzzlement over' -@b. 

theresults,andpointedupsomedeficienciesin I

large-scale photography. 

Photo scale is variable on Some photos. 

Film speed is difficult to keep synchronized 

with ground speed because of fluctuations in 

ground elevation and flying height. Such distortions can create serious errors. Even more 

important is the effect of tree height on large 

photo scales. If scale at ground is 1 inch = 

1M) feet, then scale at top of 50-foot trees is 

1 inch = 89 feet, and scale at top of 100-foot 

trees is 1 inch = 76 feet, These fluctuations in 

photo scale cause serious errors in photo interpretation. 

The winter pictures were exposed to resolve e 

the dark ground.. Thus the lighter tree tops 

were overexposed. Tree measurements were difficult tomake, sometimes impossible. If there 

had been snow on the ground, the results would 

have been better. 

The summer pictures caught the trees in 

full foliage, and at large scales that is e hindrance. We could not see the tree trunks or the 

ground. Individual trees could not be distinguished by crowns alone, especially in dense 

stands . 
r 

:.F ,! The photo interpreters. who took pert in , ' 

F* this study were thoroughly experienced with f.I > 

ti smalles-scale photos, but had had no experience 1- ' ,' 'with-large photo scales. Men thoroughly experi- ,I 

, - meed with large-scale photos no doubt hould get 

better results from- them. , Z i 

i' 

In forest survey work, the large-scale 

1 -- $hot~~. as now taken with the Some camera appar-. . I.? , ently have no advantage over conventional small- . , scale photos. However, if the photos were.taken 

when there is snow on the ground, and f f phto 

interpreters became experienced enough with 

L=- large-scale photography that they could overcbms 

scale distortions, then this type of aerial pho- 

$ography could be used in 'forest survey work. 

RABBITS DAMAGE METASEQUOIA 

I PLAYTINGS AT BGLTSVILLE, XD. 

Several small plantings of Metasequoia 

(~etase~uoia g1yptostroboides)--the species that 

had been thought extinct until living specimens - were found in China a few years ago--were made 

at the Beltsville Experimental Forest in the 

spring of 1950. The trees were planted on several sites in the forest and in the nursery. 
\ 

River bottom . 1 (hardwood overstory) 

, 

Rf ver bottom 

(pine ouerstory ) 

Sandy soil 

(beech overstory) . 

Nursery f 

I 

Aabbits seem to be the most serious enemy 

of Metasequoia in the Beltsville area. 09 43 

trees planted, 27 were injured and 5 were killed 

by rabbits during the winter. The tree does have 

the ability to recover following severe injury 

by rabbits. In one case the entire top of a 

tree was clipped off', leaving a 3-inbh sttlb 

above 'ground. A new shoot developed and grek 

14 inches by the end of the growing season. 

--M I J . WLLIAP@SOTJ 

AGRICULTURE - FOREgT SERVfCE - UPPER OARBY, Ph. 

I