Biomass production and carbon stocks of poplar-based agroforestry with canola and wheat crops: a case study

Poplar (Populus deltoides Bartr. ex Marsh.) produce a large amount of biomass per unit area and is important fast-growing species in different planting systems. However, the appropriate space between poplar trees is essential to high-performance productivity in diverse regions. The present study monitored the effect of different spacing configurations (A: 4 × 3 m; B: 4 × 3 m (pure poplar); C: 6 × 3 m; D: 8 × 3 m; E: 10 × 3 m and F: pure crop) of poplar-based agroforestry with two canola (Brassica napus L.) and wheat (Triticum aestivum L.) cropping system on biomass production and carbon storage. Over the eight years, the total poplar biomass production was significantly different (P ≤ 0.05) in poplar-based configurations and ranged from 9.1 to 13.4 mg ha–1. The highest carbon storage of 6.5 mg ha–1 was observed in configuration E. Crop production of canola and wheat in configurations B, C, D, and E, did not show a significant difference with pure crop cultivation, while configuration A was significantly lower. Our result indicated that configuration E, with the highest total biomass production but no significant difference in crop production, is the optimum system of poplar-based agroforestry in regions with similar temperate climate conditions of Northern Iran. Finally, poplar-based agroforestry provides high efficiency of carbon sequestration in trees which can conserve all market and non-market benefits.
Keywords: aboveground biomass, carbon concentration, crop yield, productivity, Populus deltoides, Northern Iran