Point transect sampling of deadwood: a comparison with well-established sampling techniques for the estimation of volume and carbon storage in managed forests

In managed forests, the occurrence of deadwood (DW) can be regarded as a stochastically rare event with strong clumping and high local variability (Meyer in Forstwissenschaftliches Centralblatt 118: 167-180, 1999). Traditional sampling techniques, such as Fixed Area Sampling, Angle Count Sampling and Line Intersect Sampling, do not regard this fact and may be inefficient for surveys of DW, because of limited search areas. A sampling technique that should remedy this shortcoming is Point Transect Sampling (Buckland et al. in Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2001; Advanced distance sampling: estimating abundance of biological populations. Oxford University Press, Oxford, 2004), where as a matter of principle, all objects that are sighted from a fixed location are counted. We compare Point Transect Sampling with the other well-established sampling approaches for the estimation of volume, necro-mass and carbon storage in terms of precision and sampling effort. It is shown that Point Transect Sampling is the superior method for sampling standing DW regarding efficiency, whereas for sampling downed DW, it is clearly outperformed by Line Intersect Sampling.