Poplar in wetland agroforestry: a case study of ecological benefits, site productivity, and economics
Poplars are the major tree component of traditional agroforestry systems throughout the south temperate central area of China that includes all or portions of Jiangsu, Anhui, Zhejiang, Hubei, Henan, Shandong, and Shanxi provinces, an area of ~600,000 km2. The lack of experidmental data on the effect of various interplanting systems on crop production represents a serious gap in our knowledge, and consequently, a stable, optimized poplar-crop interplanting pattern is difficult to achieve. In order to develop a poplar-crop interplanting pattern that is economically viable, environmentally sound, technically workable, and socially compatible in floodplain areas, new poplar-crop interplanting patterns were designed using the principle of edge effects. Six patterns were designed and established in 1992 with different narrow – wide spacings, i.e., I: (3 × 3) × 20 m, II: (3 × 3) × 30 m, III: (3 × 3) × 40 m, IV: (4 × 4) . 20 m, V: (4 × 4) × 30 m, and VI: (4 × 4) × 40 m. A randomized block arrangement was used with two replications for each pattern. Based on 7 years of investigation, this paper examines the effects of these patterns on temporal and spatial variations in microclimate at various phenological phases of winter wheat, variations in wheat yield and quality, wood production, biomass productivity and light use efficiency, and economic assessment. The feasibility and viability of these new patterns is also discussed. These preliminary results provide some basic principles for developing optimized poplar-crop interplanting patterns in the wetland plain areas of China.