Stemflow estimation in a redwood forest using model-based stratified random sampling

Abstract

Model-based stratified sampling is illustrated by a case study of stemflow volume in a redwood forest. The approach is actually a model-assisted sampling design in which auxiliary information (tree diameter) is utilized in the design of stratum boundaries to optimize the efficiency of a regression or ratio estimator. The auxiliary information is utilized in both the design and estimation phases. Stemflow and its variance were modelled as powers of diameter and a generalized non-linear least squares model was used to estimate the exponents and to impute values for missing storm events prior to application of the ratio estimator. The advantage of the ratio estimator over standard stratified sampling formulas is greatest for species in which stemflow is strongly dependent on diameter. With measurements on 24 trees in a 1-hectare stand, annual stemflow was estimated with coefficients of variation of 9 per cent and 10 per cent in 2 years of study. Striking stemflow differences were found between species. Published in 2003 by John Wiley & Sons, Ltd.

Citation

Lewis, Jack. 2003. Stemflow estimation in a redwood forest using model-based stratified random sampling. Environmetrics 14(6):559-571.