Tree Growth Strategies: Douglas Fir Budburst

Within a tree species, there can be substantial variation in many characteristics such as the timing of spring budburst and the rate of shoot growth. This clip shows two seed sources of Douglas-fir growing on a site near Centralia, Washington. The source on the left (from the southern Oregon Coast) bursts bud and starts growing almost a month before the source on the right (from the Washington coast). Early budburst can have the advantage of completing more growth before soil moisture becomes limiting, but it runs the risk of frost damage if it occurs too early. Later timing of budburst has less of a risk of spring frost damage, and may not expose foliage to browsing until alternative browse is available, but plants that burst bud late may have less time to complete their growth before summer droughts. Many strategies have evolved over time. Some will be more successful in some years on some sites than others. Which one will win in this race?