Estimation of aboveground biomass for alpine shrubs in the upper reaches of the Heihe River Basin, Northwestern China

Shrubs are important components of alpine mountain ecosystems in terms of productivity and diversity. An estimation of shrub biomass using allometric equations represents a non-destructive option for obtaining useful quantitative data. However, species-specific allometric equations for alpine shrubs have yet to be developed in sufficient detail. This study proposed allometric equations that can be used to estimate aboveground biomass of alpine shrubs. These are based on easily acquired descriptive parameters of plant height (H), crown area (C), basal diameter (D), and D2H (basal diameter squared × total H) for four of the most abundant alpine shrub species in the upstream ecosystems of China’s Heihe River Basin: Salix cupularis, Salix oritrepha, Potentilla fruticosa, and Caragana jubata. The results show that several equations relating biomass categories to H, C, and D2H provided significant (P < 0.01) data for measuring aboveground biomass; the determination coefficients (R2) varied from 0.95 to 0.97 and fit indices (FIs) varied from 0.96 to 0.97. The form and variables comprising the allometric equations differed among species-specific models. Aboveground shrub biomass increased with D2H for S. cupularis and C. jubata, whereas it increased with C and H for P. fruticosa. For S. oritrepha, an exponential function provided the best-fit model with C. However, the results could provide useful approximations of aboveground biomass of similar shrubs currently lacking such equations. The allometric equations also provide a useful and non-destructive method of estimating aboveground shrub biomass in alpine ecosystems.