[Growth and reproduction of Rosa multibracteata population in Minjiang River dry valley]

Based on large area field survey and sampling plots investigation, this paper analyzed the distribution, growth and reproduction, and spatial differentiation of native Rosa multibracteata population in the dry valley of Minjiang River. The results showed that this shrub was widely distributed within the area about 170 km long and across the altitude between 1 200 m and 2 600 m from Mianchi Town of Wenchuan County to Zhenjiangguan of Songpan Town. The plant height, base diameter, age, canopy area, sprout number per clump, and hip number each cluster of the shrub were averagely (123.33 +/- 3.13) cm, (12.49 +/- 0.40) mm, (3.34 +/- 0.16) a, (1.30 +/- 0.13) m2, (5.07 +/- 0.39) stem/cluster, and (171.47 +/- 25.90) hip/cluster, respectively. Except the sprout number per cluster, all test parameters showed significantly higher values with increasing altitude and latitude, being most likely related to the improvement of water condition. The increasing fruit output and sprouting number with increasing altitude and latitude was closely related to the better growth, and possibly, to the trade-off of sexual and asexual capability of R. multibracteata across the changing environment. The lack of younger clusters in age structure indicated the instability of the population development, but the fact that the population had bigger ratio of older sprouts and bigger age structure with increasing altitude showed the sustainable development of the population. The stronger capability of R. multibracteata in growth, sprouting, and sexual reproduction in the dry valley of Minjiang River provided reliable guarantee for the sustainable development of the population.