RESEARCH METHODS IN STUDY OF FOREST E N VI R< , X M 1 . \)\ 



It is desired to present another set of data obtained by Bates LO 

 to illustrate the need of establishing the wilting eoefficienl 

 particular species in which one may be interested and. therefor* 

 establishing a specific relationship between the wilting coefficient* 

 the capillary moistures of the same soils. This presentation also 

 assists in showing, what has already been mentioned, thai a measu 

 of the capillarity or other moisture relation of the soil has an indirect 

 value in permitting comparisons of the species under a variety of 

 conditions. 



The tests as presented in Table 3 were performed on five distinct 

 kinds of soil, varying as to origin (hence, chemically) and also con- 

 siderably as to composition and water-holding capacity. With the 

 exception of the prairie soil, which contained only 1 per cent of coai 

 sand and no gravel at all, these soils were prepared by pas-mir through 

 a sieve with quarter-inch meshes. 



The wilting coefficient determinations, moreover, were made with- 

 out the use of paraffin. As the test was designed particularly to com- 

 pare, the four species which were grown in each soil, and it had he- 

 come apparent that the rooting habit of each had a good deal of heat- 

 ing on the stage in soil drying at which it succumbed, the effort was 

 made to keep the upper layer of the soil well supplied with moisture 

 by daily watering. As a result, the common drying of the stem just 

 at the ground line was not appreciably in evidence and, indeed, so 

 general was the drying that the determination of the end point was 

 exceedingly difficult. It was based almost wholly on the flaccidity «•( 

 the leaves. Whether because of this protection afforded the stem- by 

 surface watering, or because of the comparative shade in which the 

 end points w r ere approached, it is noteworthy that the ratios of wiltii 

 coefficients to capillarities are much lower, except for the heaviest 

 clay, than in the results obtained under different condition- and 

 already described. 



Another noteworthy feature of this test is that the seedlings were 

 produced in each soil with the moisture brought daily to the moisture 

 equivalent, so that the availability was, as nearly as could then be 

 calculated, the same in all cases. When drying began, each -oil 

 was brought by easy stages to two-thirds of the moisture equivalent, 

 and finally to one-third. The seedlings attained an age about 

 months before the test was completed. 



