Effects of light intensity and clipping treatment on the compensatory growth of Caragana korshinskii seedlings

Under 3 light intensities of 100% natural sunlight (NS), 37% NS and 16% NS respectively, the experiment was conducted to investigate the effects of light and clipping intensity (non-clipping, stubbled 30 cm, stubbled 20 cm, stubbled 10 cm and stubbled 3 cm) on compensatory growth of two-year-old Caragana korshinskii seedlings. The results showed that: 1) High light and clipping treatment facilitated compensatory growth of C. korshinskii seedlings. Both the sprout number and basal stem diameter of sprout of clipped seedlings maximized under high light intensity, while a decreasing trend was observed with the increasing of clipping intensity. 2) Shoot height (SH), basal stem diameter (BSD), taproot length (TRL), and lateral root number (LRN) of clipped seedlings all presented in the order of 100% NS>37% NS>16% NS in all clipping treatments. SH and BSD of clipped seedlings were lower than those of control and declined with the clipping intensity increasing. Slight clipping treatment accelerated taproot growth and increased LRN, while they were inhibited when clipping intensity increased. 3) High light facilitated the accumulation of biomass of clipped seedlngs, but a decline of total seedling biomass was detected with the increasing of clipping intensity, in another words, biomass accumulation of clipped seedlings appeared as under-compensatory growth. With the decline of light intensity, the compensation index of biomass of clipped seedlings increased and only slightly fluctuation among different intensities of clipping under the lower intensity of 16% NS, suggesting that the biomass accumulation of clipped seedlings mainly depended on new carbohydrate from photosynthesis under high light intensity and on nutrient supply from the root system and stubble under relative low light intensity. The results indicate that the ability of compensatory growth of clipped C. korshinskii seedlings declined with the increasing of clipping intensity and appeared as under-compensatory growth, and that high light can facilitate compensatory growth and biomass accumulation of clipped C. korshinskii seedlings. This result would provide reference for seedling cultivation, forage production and management of grassland ecosystem.