The cumulative effects of recurring dry conditions are not visible until future years.
Water stress affects most of the physiological processes involved in plant growth.
Under drought conditions, plants become more susceptible to disease and pest infestation. As is true with people, weak, stressed trees are more vulnerable to problems. These pests may push trees in a marginal state of health over the edge to death. This leaves only a small percentage of deeper anchorage roots. For the most part, it is these surface roots that absorb water and nutrients needed by the tree.