Crown condition, needle mass, and sapwood area relationships of Norway spruce (Picea abies)

Crown-condition assessment, hypothesized to estimate needle losses followin g damage from several sources, one of which might be air pollution, suffers from the subjective notion of a standard "healthy" tree. On the other hand , the foliage biomass - sapwood area ratios are reported to depend on a num ber of factors, e.g., site quality, stand density, crown class, and tree ri ng width conductivity. The authors hypothesize that early sapwood area migh t help to even better estimate needle biomass of Norway spruce (Picea abies (L.) Karst.) and to help standardize crown-condition assessment. Thirty-si x Norway spruce trees at two Austrian sites, from three age-classes, three crown classes, and two crown-condition classes were felled. Needle mass, cr oss-sectional area, sapwood area, and early sapwood area (i.e., sapwood are a excluding latewood) were measured. The results of this study indicate tha t indeed early sapwood area is a good estimator of foliage, independent of site, age, crown class, and crown condition. The ratio between early sapwoo d area and cross-sectional area could be a good estimator for crown conditi on and thus help to standardize crown-condition assessments by different su rveyors.