Abstract: Ephemeral plants are a unique group of flora in Xinjiang. Studies on growth and resource allocation are helpful in understanding their survival strategies. Bromus tectorum L. is a typical ephemeral plant in northern Xinjiang, playing an important role in the spring pasture restoration. In this study, we examined the phenological rhythm, growth dynamics, biomass allocation and reproductive output of B. tectorum distributed in Junggar Desert. Seedlings emerge in late fall, survive overwinters under snow, reach their maturity in late spring and die in early summer. In spring, B. tectorum grows rapidly and shows a fast development rhythm, which takes 52 days from tillering stage to maturity. With plant development, aboveground biomass increased rapidly, belowground biomass increased slowly, and root/shoot ratio decreased from 0.6 at tillering stage to 0.13 at fruit ripening stage. With the rapid decrease of root/shoot ratio, plants shifted from vegetative growth stage to reproductive growth stage. There is allometric relationship between reproductive biomass and vegetative biomass, and between belowground biomass and aboveground biomass. With increasing plant size, the reproductive output increased linearly, thereby reproductive allocation remained relatively stable (39%). The rapid growth-development rhythm and resource allocation strategy of B. tectorum in spring can achieve stable reproductive output of individual plants of all sizes, which has important ecological significance in maintaining population renewal and reproduction.

Key words: phenology, growth dynamics, ratio of root to shoot, reproductive allocation, allometry, Bromus tectorum