Pushing through a patch of dense spruce and fir at the top of W6, we emerge onto an old logging road at the top of Watershed 5. W5 was clearcut in 1983, so the trees are still short enough to see over.  We call this the "lunch spot" and it has the best view in the Hubbard Brook valley.  This view is to the southeast, but we can also see Mt. Washington to the east and Lafayette Ridge to the northeast.

        Historically, spruce was more common throughout the Hubbard Brook valley, but spruce logging in the late 1800s and early 1900s favored the regrowth of hardwoods.  (Click here to see a core from the oldest spruce yet discovered in the Hubbard Brook valley.)  Today individual spruce are occasionally seen at lower elevations, but on the south-facing slopes, the greatest concentrations are close to the ridgetops where the winter climate is a bit too extreme for most hardwoods.  On north-facing slopes, where winter snowpacks take longer to melt, this "spruce-fir" zone extends farther down the slope.

        Moose were observed to return to the Hubbard Brook valley in the early to mid 1980s.  Today there is a sizable population here, judging by the abundance of moose scat.  Moose prefer to eat the leaves and twigs of hardwood species over conifers, and browsing the shorter saplings that are within their reach, they consume many of the hardwood saplings, leaving the conifers behind.  By doing so, they may be encouraging the regrowth of spruce at lower elevations, but this possibility has not yet been studied at Hubbard Brook.

 

This is a view looking back into W6 from the old logging road at the top of W5.  The tall spruces in W6 display some slight "flagging"--the absence or stunting of branches on the side of the tree facing into the prevailing winter wind.  Flagging is only seen in individuals that are above the general canopy level and, therefore, are exposed to the wind.  It is caused by abrasion damage from ice crystals and is a testament to the severity of winter storm winds on the top of this ridge.  Below is a tree ring history from one of those spruces at the top of W6 near the edge of W5.  Although there is still some annual fluctuation in growth, this tree's growth rates have stayed pretty low since the W5 clearcut.  Although it is certainly possible that increased exposure since the clearcut may be stressing the tree, we can't know for sure without comparing growth rates of similar high elevation spruce, including some that are nearby but not exposed on the edge of the clearcut.

        This tree ring history was developed as part of a student study in tree growth trying to identify years of consistently poor growth amongst all species in the Hubbard Brook forest.  The consistently "bad" years were found to be 1923, 1936, etc.  However, no clear causal mechanism (for example, severe drought or insect defoliation) was discovered to account for any of these years of poor growth.  Unfortunately, biogeochemical monitoring did not start in W6 until 1963, one year after the last of the overall poor growth years.  Otherwise, streamwater chemistry could have perhaps provided a clue.  The trend of increasing growth for this tree in the 1940s is perhaps in response to localized effects of the 1938 hurricane.  Surrounding trees may have blown over or lost their crowns, leaving an open canopy that this tree would have rapidly grown into.

        This concludes our tour of Watershed 6.  We hope you enjoyed the trip and that you will visit again soon!!

Web page created October 2001
by Ellen Denny and Thomas Siccama