Abstract: Farmland shelterbelt is an important ecological barrier of “the Granary of Central Plains” in the eastern Henan Plain. Root cutting and film mulching can effectively alleviate the negative effects of shelterbelt on cropland, with impacts on tree growth. Taking Paulownia fortunei in farmland shelterbelts in the eastern Henan Plain as the research object, we explored the effects of different distances (1, 2 and 3 m) of root cutting and film mulching on photosynthetic characteristics of P. fortunei, to reveal the growth effect and internal mechanism of P. fortunei after root cutting and film mulching from the perspective of photosynthetic physiology. The results showed that: (1) Root cutting and film mulching significantly reduced net photosynthetic rate (P_n), and the effect of the short distance (1 m) treatment was the most obvious, which had a negative effect on the photosynthetic capacity by significantly decreasing P_n and transpiration rate (T_r); (2) Long distance (3 m) treatment mainly caused a significant decrease in P_n, but had little effect on T_r, resulting in a significant decrease in instantaneous water use efficiency (iWUE), which was not conducive to plant growth; (3) Results of random forest analysis showed that leaf P_n and iWUE were the main indices responding to different distances of root cutting and film treatment. Comprehensive comparison showed that root cutting and film mulching 2 m away from the trunk of P. fortunei had strongest photosynthetic capacity and highest iWUE.

Key words: farmland shelterbelt, root excision, Paulownia fortunei, photosynthetic characteristics, random forest