Improving shrub biomass estimations in the Qinghai-Tibet Plateau: Age-based Caragana intermedia allometric models

Caragana intermedia (Kuang & H.C. Fu) is a dominant species of the Qinghai-Tibet Plateau. The allocation of above- and below-ground biomass was studied in four different aged shelterbelts in the Gonghe Basin. Results show the relative portion of foliage biomass to total shrub biomass decreased from 32% in three-year-old shrubs to 8% in 37-year-old shrubs, whereas the relative contribution of branch and fruit biomass increased during the early years and slightly decreased later. This was the opposite for root biomass contribution as shrubs aged. Relative to three-year-old shrubs, the mean above- and below-ground biomass increased by 128%, 399%, and 646% and by 67%, 271%, and 678% in the 12-, 27-, and 37-year-old shelterbelts, respectively. Relationships between biomass of individual shrub components and shrub parameters changed with age and thus provided age-specific allometric equations. Age-specific equations need to be considered to improve biomass and carbon sequestration estimates in unstable dune and arid regions.