Assessment of allometric algorithms for estimating leaf biomass, leaf area index and litter fall in different-aged Sitka spruce forests

The relationship between leaf area and diameter at breast height (d.b.h.) or sapwood area (AS) has been used to estimate stand leaf area or biomass of forest canopies. It has been suggested that intra-specifi c variations in the relationship between stand leaf area and d.b.h. or AS can introduce a systematic error in these estimates for younger and older stands unless additional parameters relating to canopy structure are included in allometric functions. We collected data from a Sitka spruce chronosequence to parametrize and test different algorithms for the estimation of foliar biomass (FB) and litter inputs over a range of forest ages. FB estimates were signifi cantly improved when additional biometric information relating to crown structure (canopy openness and height of live crown) was included in the models. Although the use of the relationship between leaf area and AS for the estimation of leaf area is justifi ed by theoretical considerations (pipe model theory), we show that d.b.h. and other canopy parameters provided the most robust estimation of leaf area across different-aged stands. Our results also suggest that the accuracy of litter input estimates depends on needle retention time and annual turnover rate, particularly immediately before and after canopy closure.