Published online by Cambridge University Press: 31 May 2012
Improved techniques are described for cleaning gauges used in measuring the oleoresin exudation pressure (o.e.p.) of large numbers of ponderosa pines. These techniques are being used in a study of the relationship of o.e.p. and bark beetle attack in westside Sierra coniferous forests. Standard hydrostatic pressure gauges (Bourdon type) were modified by the addition of a threaded extension made of steel rod which permitted both insertion into a tree and newly-designed cleaning rack. A 9/32-in. hole in the steel rod reduced to a minimum the amount of oleoresin exudate necessary for an accurate reading. The cleaning racks, each accepting 30 gauges, were capped to confine the solvent (xylene) under pressure.