Estimation of nutrient content of woody plants using allometric relationships: quantifying the difference between concentration values from the literature and actuals

The objective of this study was to evaluate the reliability of allometric methods for assessing biomass and nutrient contents of woody species at the stand scale. Allometric relationships were built from 13 stands of a woody species of moderate height (European gorse: Ulex europaeus L.). In eight other stands, the above-ground biomass of the species was estimated using allometric relationships. Total nutrient contents (N, P, K, Ca, Mg) of these eight stands were also computed either with nutrient concentrations obtained from local stratified samples or with values derived from the literature. The estimated above-ground biomass was consistent with the measured values obtained by complete harvest of the stand. The nutrient contents calculated using the local samples were also in agreement with measured values. Conversely, the use of nutrient concentrations values derived from the literature led to significant errors which were up to 104 per cent in the estimation of nutrient contents. We conclude that allometric methods can give reliable and accurate estimates of above-ground biomass and nutrient content of woody species, provided that the values for nutrient concentrations are obtained from local samples and not from average values found in the literature.