Improved Needle Point Frames for Exact Line Transects

Abstract

An improved needle point frame for exact line transects in dense herbaceous vegetation was developed (Fig. 1). The apparatus consists of a rigid duralumin bar (B) of about 2.40 m long, with rectangular section (10 cm x 1.8 cm) bounded, at both ends, by a tightening nut system (S). After pushing into the soil two supportstakes (PS), the bar is fixed horizontally at the desired height, by the tightening nut system and with the help of a nivel, in such a way that the point of the needle (A), at its highest position, should be just above the “roof” of the vegetation. The upper part of the bar (B) is a ball-race and shows 80 small alveoles (a) spaced 2.5 cm center to center. The diameter of these alveoles corresponds to the diameter of a small ball linked to a sliding system (SC) surrounding the bar. This sliding system includes mainly two holes (0, and 0,); which command the vertical position of a needle-holder (PA), a handle (b), a ball (u) held by a flexible rod (f) and a rubber-covered metallic cylinder (CM). This produces a sliding friction between the system (SC) and the bar, whose corresponding part is covered with a strip of emery-cloth. This hole allo,ws the rapid, easy and regular movement of the needle.