Abstract: With Welsh onion Zhangqiu as the contrast, this paper measured the physiological indices including electrolyte leakage, malondialdehyde content, protective enzyme activity, chlorophyll content, photosynthetic rate and root vitality of two introduced Welsh onion varieties Chunwei and Changbao, and identified their cold tolerance and wintering cultivation effect. The results showed that during wintering cultivation, all test Welsh onion varieties suffered low temperature stress, which led the electrolyte leakage and malondialdehyde content arrived at the maximum, while the chlorophyll content and photosynthetic rate dropped to the bottom at 15 January. At this time, the function data of physiological indices were 0.452, 0.364, and 0.226 for Chunwei, Changbao and Zhangqiu, respectively, suggesting that Chunwei had stronger cold tolerance, followed by Changbao, and Zhangqiu. The bolting rate of Chunwei, Changbao and Zhangqiu when harvested was 0, 35.2% and 81.0%, respectively. Although the biological yield of Changbao was 25.67% and 52.94% higher than that of Chunwei and Zhangqiu, respectively, the economic yield of Chunwei was the highest (5.49 kg·m^-2), with an increment of 18.57% than Changbao, and that of Zhangqiu was only 0.86 kg·m^-2. It could be concluded that Chunwei was fit to cultivate in low tunnel in winter,while Zhangqiu was weaker in cold tolerance and not fit to wintering cultivation.

Key words: Shelterbelt, Imitating normal forest, Sustainable management, Spatio-temporal pattern, Ecological services