Although the general ideas David Mildrexler wrote (the column “Large trees are vital to protect water,” in the Jan. 29 print edition of the East Oregonian) regarding large trees and water cycles are true, I believe many of the specific ideas and examples are misleading. General statements such as “the largest trees have the deepest roots” and “among the most abundant forest types in the Blue Mountains (is the) fir/spruce forests” show his lack of understanding of the individual species that make up the forests around us.

Tree root depth is a function of tree species, location and age. In general, dry-site adapted tree species grow deeper roots than species adapted for moist sites. Spruce trees are adapted to moist sites and are very shallow-rooted. This is why they tend to blow over and one reason they do not make good urban trees. However, species such as ponderosa pine that are adapted to dry sites develop deep tap roots. Grand fir have only moderately deep roots. Ponderosa pine can access water that more shallow rooted species such as grand fir and spruce cannot. In addition, individual trees growing in deep soils tend to have deeper roots than the same species of trees growing in poor soils.

In contrast to what Mr. Mildrexler said, spruce/fir forests are not the most abundant type in the Blue Mountains but among the more uncommon. The grand fir/Douglas-fir forests of our mid elevations are probably the most abundant forests in the Blue Mountains. These are quite different than high elevation spruce/fir forests. Grand fir in particular is regenerating well under current conditions. Grand fir seedlings can sprout and survive in shaded conditions where most other species cannot. As a result, many areas previously dominated by ponderosa pine, western larch or Douglas-fir are now becoming dominated by grand fir. However, grand fir trees are not very fire resistant. Even 21-inch grand fir cannot survive fire that consumes the duff around their base. Ponderosa pine, western larch and Douglas-fir are longer lived and more drought and fire resistant than grand fir.

Comparing the forest floor temperature of a spruce/fir forest to a ponderosa pine forest is like comparing apples and oranges. While we can and do grow apples in Northeastern Oregon, we cannot grow oranges. Spruce cannot grow where ponderosa pine thrive and vice versa. We will never have mature spruce where mature ponderosa pine or Douglas-fir is now growing.

The 21-inch rule on east side National Forests of Oregon and Washington was put in place in 1994 to protect large trees after a time of intensive logging. It is 30 years later, and with each passing year living trees add diameter growth to their stems. Many more trees are over 21 inches now than in 1994. Our longer, hotter summers are decreasing the water available for trees. Without management, trees die as they grow larger every year and experience more competition with their neighbors. Without management the fire and drought resistant ponderosa pine, western larch, and Douglas-firs are being replaced by grand fir that can sprout and grow in the shade.