Abstract: Study on the structure of Sibiraea angustata shrubs at Kaka valley, Songpan county in Northwestren Sichuan (eastern edge of Qinghai-Tibetan Plateau) showed that its architecture was significantly influenced by grazing interference. Total biomass, total leaf area and sapwood area of individual ramets decreased significantly under heavy grazing intensity. Single leaf length, width and area enlarged significantly under moderate and heavy grazing intensities. Though maximum individual height was reached under moderate grazing intensity, the extent of aggregation of leaf and shoot biomass at top part decreased. The variation of architecture did not change the leaf area supported by unit sapwood area. Phenotypical plasticity under grazing is still controlled by Huber value to maintain the balance between leaf transpiration and hydraulic conductivity of stem.

Key words: grazing interference, Sibiraea angustata, architecture, hydraulic balance