Evaluation of Comprehensive Effect of Different Agroforestry Intercropping Modes on Poplar

Abstract

Forest–agriculture complex management is an efficient planting mode that can effectively improve soil utilization and bring greater economic value. However, this planting model has not yet been systematically carried out in the northeast of China. Thus, to provide a theoretical basis for agriculture and forestry intercropping in northeast China, the variation in the growth and wood characteristics of Populus cathayana × canadansis ‘xin lin 1’ and the economic benefits of intercropping crops under different intercropping patterns were analyzed. The results of a variance analysis show that there were significant differences in tree growth and wood characteristics among the different intercropping modes (p < 0.01). The variation coefficients of growth and wood characteristics ranged from 28.23% to 55.79% and 2.03% to 10.65%, respectively. There were significant correlations among tree height, diameter at breast height, ground diameter and wood volume of ‘P. ‘xin lin 1’, as well as between cellulose, hemicellulose, lignin, fiber length and fiber aspect ratio (r < 0.05). Meanwhile, we comprehensively evaluated intercropping modes based on growth traits such as tree height, chest diameter, diameter, wood volume and crown width. The ‘P. ‘xin lin 1’ + soybean’ mode proved to be the best intercropping mode, in which the gain of tree height, chest diameter, diameter, wood volume and crown width were 26.80%, 20.09%, 15.76%, 63.41% and 8.33%, respectively. When considering wood traits, the optimal intercropping pattern was ‘P. ‘xin lin 1’ + Cilantro + Cabbage’, but the gain of each wood trait in this pattern was not obvious compared with the total average. Among the six intercropping modes, ‘P. ‘xin lin 1’ + Watermelon + Chinese cabbage’ and ‘P. ‘xin lin 1’ + Cilantro + Chinese cabbage’ have the highest economic benefits, reaching 48,138 CNY/hm2 and 39,990 CNY/hm2, respectively. From our results, the poplar growth and wood characteristics under different intercropping modes are better than those of the pure forest, except for ‘P. ‘xin lin 1’ + Corn’, and each intercropping mode has higher economic benefits. These findings provide a scientific basis for alleviating the competition between local forestry and agriculture for land and address the selection of forestry and agricultural intercropping modes.