Quantitative traits, age structure and self-thining rule of three shrubs on northest edge of Qinghai-Tibet plateau

The quantitative traits (plant height, crown diameter, number of branches, plant weight and branch weight), age structure and self-thinning rule of Potentilla fruticosa, Salix cupularis and Rhododendron capitatum on the northeast margin of the Qinghai-Tibet Plateau were studied. We constructed the estimation model of plant biomass of this three shrubs, determined their age structures, and clarified the self-thinning relationship between the number of branches and branch weight for each shrub. The results showed that: 1) The impact on the plant weight by the quantitative characteristics of each species was Potentilla fruticosa > Salix cupularis > Rhododendron capitatum; 2) The crown diameter could be used as a suitable index for estimating the shrub plant weight, the estimation models of plant weight (PW, kg) basing on the crown diameters (CD, cm) were PW = –0.310 + 0.014CD for P. fruticosa, PW = –1.688 + 0.033CD for S. cupularis and PW = –0.203 + 0.013CD for R. capitatum, respectively; 3) S. cupularis and R. capitatum was a growing population and had a certain stability, while the P. fruticosa belonged to a stable population; 4) There was an obvious self-thinning law between branch weight and number of branches of R. capitatum. This research shows that the quantitative traits, age structure and self-thinning law for each species is different, which suggests that it is an adaptive result to different habitats and nutrient resources.