On the field performance of transect relascope sampling for assessing downed coarse woody debris

Transect relascope sampling is a recently proposed method for making effici ent inventories of coarse woody debris on the ground. However, before the m ethod call be recommended, its performance in the field requires investigat ion. This paper presents the results of a field study in which 11 surveyors tested the method in two coniferous stands in northern Sweden. The average bias introduced by the surveyors was moderate under normal sighting condit ions, but underestimation was substantial when combining a small relascope angle with poor sighting conditions. In all cases, the differences between the systematic errors of individual surveyors were substantial. The conclus ion is that transect relascope sampling is not an appropriate method when t he demand for unbiased estimates is high, e.g. in connection with long-term monitoring, but that the method can be useful as a first phase in double s ampling or in ocular-based inventories aimed at identifying biologically va luable areas.