ABSTRACT Project 3.3 obtained experimental data on three natural tree stands in support of studies in predicting blast damage to forested areas. Primary objectives were: 1) to determine blast damage to trees in terms of stem breakage, limb breakage, and defoliation where effects are influenced by their location in a natural tree stand; 2) to determine the effect of natural forest cover on the shock wave in terms of its peak static overpressure and peak dynamic pressure attenuation; 3) to provide individual tree deflection data in the region of long positive phase duration times in order to support the theoretical basis for breakage prediction. The tree stands on three separate islands varied from 29 to 170 acres in area with vegetation composed of broadleaf trees up to 80 ft tall and coconut palms about 40 ft tall. Several paims on the three islands were equipped with snubber wire arrangement for measuring maxi- mum deflection. The large stand was instrumented with 16 self-recerding ground-level static overpressure gages at eight locations and two selfrecording dynamic pressure gages at two locations; the two smaller stands were, instrumented with two static cverpressure gages each. Sample plots were established on two islands for assessing stem and limb breakage in more detail. Ground-level pressure measurements lengthwise of a large stand showed no attenuation in peak static overpressure. It was not possible to evaluate the degree of peak dynamic pressure attenuation because gages both in front of and inside the tree stand messured unrealistically high peak dynamic pressure compared to values calculated from corresponding peak static overpressure measurements. Nonuniform character of stands prohibited evaluation of shock attenuation from observations of tree damage with distance. The damage to the broadleaf trees was principally crown damage with occasional stem breakage or uprooting. The type of damage experienced was similar for moderate and high yield weapons. Observed damage from two weapons cf different yields compare favorably with isodamage curves prepared for broadleaf stands. SECRET- RESTRICTED DATA wee oe teteed ~"" ‘