中文摘要：

本研究通过试验模拟了不同强度的地上生物量刈割扰动（对照,30%,50%和70%）,并监测了试验沙拐枣幼株的光化学特性,旨在研究补植灌木人工刈割作为饲草过程中,地上生物量负向扰动对沙拐枣幼株光系统Ⅱ（PSⅡ）光化学过程的影响。结果显示,扰动强度与幼株光化学过程的响应并非简单线性关系;扰动30%地上生物量的幼株表现出最高的PSⅡ光化学效率与光合能力;高强度地上生物量负向扰动下,虽然幼株能通过自身调节机制保证PSⅡ的正常功能与完整性,并能在光化学过程被抑制时通过热耗散消耗多数过剩激能,使过剩激能份额保持稳定,但是高强度的扰动（〉50%）将降低幼株光合能力,电子传递速率及光化学效率与活性,并最终影响幼株的正常生长。

英文摘要：

The effect of artificial disturbance on aboveground biomass of two years old Calligonum caput-medusae saplings was studied using different disturbance intensity（CK,30%,50% and 70%） and assessiing photochemical processes in PSⅡ of reforested shrub saplings.Saplings in the 30% disturbed group had the highest photochemical efficiency of PSⅡ and photosynthetic capacity.Most of the surplus absorbed energy by PSⅡ of experimental saplings could be dissipated as heat when the fraction of absorbed light utilized in PSⅡ photochemistry was inhibited,thus the excess excitation energy maintained a stable status.The saplings under high intensity disturbance could maintain the normal function of PSⅡ by series regulation and photoprotection mechanisms.However,high intensity disturbance of aboveground biomass（more than 50%） reduced the photosynthetic capacity,electron transport rate and the efficiency and activity of PSⅡ thus inhibiting the growth of saplings.