Growth and biomass allocation dynamics of Artemisia ordosica in sand-fixing vegetation of the Tengger Desert of China.

Abstract

Aims Resource allocation pattern is an important trait of plant ecological adaptive strategy. The composite sub-shrub Artemisia ordosica is widely distributed in the sandy land of northern China and is an important sand-stabilizing plant. However,its growth dynamics and resource allocation pat-terns are poorly known. Our objectives were to determine:1) the growth dynamics of vegetative and re-productive organs and the biomass allocation pattern in different growth periods; 2) the relationship between reproductive and vegetative growth and 3) variations of biomass allocation pattern with age of sand-fixing vegetation. Methods A field experiment was conducted on revegetated areas in Shapotou,located at southeastern fringe of Tengger Desert,from April to November 2007. Twenty-five A. ordosica were sampled monthly in sand-fixing vegetation planted in 1956,1964,1981,1987 and 1991 to measure the number,size and biomass of vegetative organs and reproductive organs such as leaves,vegetative shoots,flow-ering shoots,capitula and seeds. Important findings In different growth periods,there were different growth rates and proportion of photosynthate allocation to organs. So the energy accumulation center and growth center vary with growth period. The vegetative growth,reproductive output and size of panicle in 2007 were significantly greater than those in the year when precipitation was less than half that in 2007,while no significant differences were found in reproductive allocation and size of capitula between these years. The individuals with greater vegetative biomass were also characterized by higher reproductive output,but the vegetative and reproductive growth were unsynchronized with different increment speed,which indicated that there was a trade-off between reproduction and vegetative growth. Annual biomass,reproductive output and reproductive allocation showed a trend of decrease with time extension of the sand-fixing project,but no statistically significant differences of the three indices were found among these five vegetation areas with different ages.