It is important to identify micro-sites on your tree farm and choose the proper species to plant on them.
Identifying these micro-sites requires a good knowledge of your land. This comes by observing the soil, moisture and vegetative cover when you are doing various activities on your tree farm. This is not really something you can trust to the average contract tree planter. There is an old saying that holds true here—"the best fertilizer for the land is the footprints of the owner".
Diversity similar to that which is found in nature is obtained by planting the proper species on these micro-sites rather than by carrying several species in your planting bag and methodically alternating the different species across your planting area. A good example of this is on a dry rocky ridge or in a poorly drained heavy soil; you may be able to grow a reasonably good crop of Valley Ponderosa pine where Douglas-fir would fail.
Some people are reluctant to plant Valley Ponderosa pine because of the lack of a local market at the present time. While nothing is for sure, there will probably be sawmills interested when there is sufficient volume available for a developing market. On many sites Valley Ponderosa pine will out grow Douglas-fir and even with lower log prices you might still net more money.
While not generally thought of as a micro-site, forest land shaded by a larger timber stand on adjacent property requires special attention. Douglas-fir seedlings do poorly in these situations even within considerable distance from larger trees. Such a location calls for plating a shade tolerant species such as western red cedar, hemlock or grand fir.
A word of caution about the planting of western redcedar. People associate western redcedar with wet sites and generally speaking this is true. However if it is wet because it is heavy soil or has poor drainage it may not be a suitable western red cedar site. A good indicator of such conditions is the presence of Oregon white ash. To do well western redcedar needs reasonably good drainage.
Where specific tree species grow is no accident. In the wild trees may be where they are for a variety of reasons. But often they are where they are because they compete better for that shady space near the stream, can stand the hot dry summer drought on a clay hillside, or simply grow faster that other species in a particular place.
To ensure success with growing trees in the Willamette valley select the tree species that will "love" the place they are planted. Simply surviving is not enough. Learn the conditions preferred by different species and be able to recognize these conditions on your property. Table 1 lists tolerance of common native species to various site conditions. Listed along the top row are factors that impact how well trees will perform. Take a look as each as it appears on the table:
Growth: This gives you a feel for how tall a tree can grow in a good location each year. When you are planting, think ahead and allow your trees room to grow. Too often land owners will plant more trees than the site can handle after only a few years.
Low light: Most trees prefer an open sun light area, yet some will do better if they are planted in a partly shaded area. Trees with a rating of 4-5 will tolerate some shade. Trees with a 1-2 rating would need full sun.
Animals: This relates to susceptibility of damage from big game like deer and elk, which can eat certain trees to the ground if hungry. If large animals are around, planting a species with a rating of 1 is like planting lunch if you don’t protect your trees.
Wet soil: Almost all species prefer deep, well drained soil. Trees need water but not too much. On sites that stay wet or soggy, look for species with 4-5 ratings. If the site is too wet or flooded for long periods, do not be surprised if no tree species thrive at all. Some areas are just destined for wetland marshes.
Drought: Annual rainfall in the valley is variable from year to year, but also varies from about 30 inches a year to about 80 depending on where in valley you are located. If you are plating trees in a low rain fall area or with rocky soils look for species with a 4-5 drought rating.
Frost: Some areas are prone to spring frosts that may continually kill the new growth on the trees. Valley bottoms are particularly susceptible to this problem. Trees with 4-5 rating will tolerate this factor better.