Drought effects on the forest

Drought occurs across the province when regions experience unusually low precipitation for an extended period of time. The effects of drought can be especially severe in areas with dry aspects and shallow, well-drained soils or areas where excessive soil disturbance has occurred.

Drought symptoms are most apparent in late summer to early fall and can occur over very large areas.

Drought Susceptibility

All conifer species are susceptible to drought conditions. While seedlings or young saplings are at particular risk due to small undeveloped root systems, understory or shallow-rooted trees can also be severely affected.

Trees undergoing moderate moisture stress will shed older needles prematurely, usually on the lower crown. Seedlings show wilting, yellowing, and necrosis of the foliage. Older trees exhibit symptoms from the tip down and from the outside inward. Affected foliage eventually turns brown or red in all species except larch. On larch, foliage turns yellow, droops, or shrivels around the stem or branches, and falls off abnormally early.

During well-advanced drought conditions, foliage discolouration and needle death become more pronounced and tip dieback may be seen. On western white pine, drought-related stem cracks are sometimes found.

Tree mortality due to drought

Drought can cause extensive mortality on young trees for the four or five years after planting. Mortality of older, larger trees is usually not widespread. Damage can result in growth reduction, dead tops, and defoliation. However, if drought occurs over several successive years, large trees of intolerant species may also die. During drought periods species or varieties of trees adapted to dry sites are more tolerant than those adapted to moist sites. Drought may increase the likelihood of insect attack and decrease the ability of the tree to defend against fungal infection and/or insect attacks.

See more information regarding drought conditions across the province at the B.C. Drought Information Portal