Correcting LAI-2000 estimates for the clumping of needles in shoots of conifers

The LAI-2000 plant canopy analyzer tends to underestimate the leaf area index (LAI) of coniferous stands because of the clumped (nonrandom) arrangement of needle area in the crown. It has been proposed that, in stands where the individual shoots constitute the most important clumping elements, the LAI-2000 gives an estimate of shoot silhouette area index rather than LAI. To obtain the true LAI, the instrument reading should then be multiplied by a correction factor accounting for the overlap of needles on shoots. Testing of this hypothesis has so far been faulty due to incorrectly estimated correction factors. We define the appropriate correction factor, and examine its range of variation based on empirical data. Previous studies on the performance of the LAI-2000 in coniferous stands are reviewed based on the results. Our aim is to advocate further testing of whether, when, and how the LAI-2000 estimate can be corrected by accounting simply for the clumping of needles in shoots.