Influence of different Taxodium ascendens stands on the open ranges and system performance in Jiangsu Province, China

This paper reveals the results of an eight-year experiment set up to identify the effects of four tree spacing configurations (1.5 × 4 m, 1.2 × 5 m, 2 × 3 m and 1.5 × 2 × 6 m) on open ranges and the relationship between open ranges and species coexistence in Taxodium ascendens-intercrop systems. Relative interrow open ranges and relative interplant open ranges were significantly different among four tree spacings. All relative open ranges (relative interrow open ranges, relative interplant open ranges, relative canopy open ranges and relative space-volumed open ranges) decreased with increasing age. The wider interrow or interplant spacings of trees offered wider (relative) interrow or interplant open ranges for intercrops. All of the tree spacings, except spacing 2 × 3 m, had negative relative interplant open ranges in nine-year-old stands, suggesting that the canopies between a plant and its neighbouring plant were in direct competition, and no interplant open range existed between two individual trees. Up to age nine, spacing 1.5 × 2 × 6 m showed no marked disadvantage in growth performance as compared to the other three spacings, but provided wider interrow open ranges for intercrops. Starting with tree stands of age four years, the yields of interplanted wheat (Triticum aestivum), soybean (Glyciae max) and rape (Brassica napus) decreased significantly as a result of the decrease of open ranges in tree stands. The yields of wheat, soybean and rape were lower in tree spacing 2 × 3 m than in other spacings. There was a positive correlation between wheat yields and canopy open ranges. This revised version was published online in June 2006 with corrections to the Cover Date.