Manipulating nutrient and water availability in a maritime pine plantation: effects on growth, production, and biomass allocation at canopy closure.

摘要

We present the results of a water and nutrient manipulation experiment in a five-year-old plantation of maritime pine (Pinus pinaster) in south-western France. Water and nutrient levels were manipulated in a factorial design with two levels of irrigation (control receiving only rainfall and irrigated) and three levels of fertilizer (control or no added nutrients, P only, and annual addition of a complete nutrient mix) to quantify the growth limitations of plantation forest in this particular area. The 5-year treatment increased the aboveground biomass annual increment by 4% in the irrigated treatment to 58% in the mixed nutrient amendment with respect to the control. The fertilizer treated plots showed slightly non-significant lower root-to-shoot ratio. The effect of irrigation was maximum in 2002, resulting in 6, 7 and 12% higher growth rate on the plots treated with mixed nutrients, the control plot and the plot added with P only, respectively. A windstorm disturbed the experiment in 1999 and has affected preferentially the fertilizer-treated plots, with the mixed nutrient plots displaying 60% damage. The higher growth rate of the fertilizer-treated and irrigated plots was attributed to increased (estimated at 5 to 15%) amount of light absorbed by the canopy, and increased (estimated at 26% for IF plots) amount of aboveground biomass produced annually per unit leaf area.