Why does forest growth decline with age?

It has been widely observed that forest growth declines with age. A recent synthesis study found that the decline in growth is primarily driven by both decreases in photosynthesis and plant respiration, with photosynthesis decreasing more rapidly than respiration with age. Decreases in nutrient availability in soils, light availability in forest canopy, and water supplies in the top canopy may explain the decrease in photosynthesis, but how genetic information expressed by tree genes controls the aging photosynthesis is not clear. This talk intends to ignite discussion how genetic traits control the response of ecosystems to the changing environment.