trees, flood-damage, soil oxygen
FLOODING’S EFFECTS ON TREES Tree health is adversely affected when the surrounding soil is temporarily flooded by the overflow of streams and rivers or when the soil is saturated by persistent rains. The primary effect of flooding is the reduction in soil oxygen. The upper 6 inches of a typical soil has an abundance of oxygen and is where the roots responsible for the absorption of water and nutrients reside. Most people are aware of photosynthesis, the process where trees “take in the bad air” (CO2) and “give back the good air (O2),” but many are unaware that living tree tissue is also respiring, taking in the good O2 and giving off the bad CO2; this applies to all the living tissue in a tree, including the roots. When flooding occurs, the soil has less oxygen for root respiration and the roots begin to die. As the roots die, the tree’s ability to absorb water decreases and the foliage begins to wilt. Paradoxically, the tree dies from the lack of water because it is standing in water—a phenomenon referred to as “physiological drought.”
Ball, John, "Flood-damaged Trees" (2011). SDSU Extension Extra Archives. 227.