The Effects of Climate Change on Temperate Rain Forests in Southeastern Alaska

            The article I chose to outline the effects of climate change can be found here: http://www.fs.fed.us/pnw/sciencef/scifi149.pdf

            Research conducted by the US Forest Service at their station in Southern Alaska over the past 13 years has highlighted a number of trends that will most likely continue as our climate continues to change.  These changes will have numerous implications on the way these forests are viewed and managed, as species ranges begin to shift.

            One trend that could have potentially positive effects on the temperate rain forest ecosystems as well as globally is an overall increase in biomass within the unmanaged forests found in Alaska.  In higher elevation areas within the range, there have been up to 8 percent increases in total biomass.  This is no small change; the amount of additional biomass in the Chugach National Forest from the past 13 years annually stores an equivalent amount of carbon to the emissions of 500,000 passenger cars over the same period of time.  While there are most likely multiple causes at play for such a large shift, the most notable is the temperature change that has occurred in these ecosystems over the duration of the study.  The average annual temperatures of Alaska’s temperate rain forests have risen 2.7° over the past 50 years.  Even though a shift of two degrees may not look particularly noteworthy, such a change would extend the growing season in these areas while simultaneously allowing trees to grow for more of the year at higher elevations.

            Another interesting effect that the climate change has brought to the temperate rain forests is a slight shift in biomass between tree species.  Some species have been much more capable than others in terms of adapting to the change in growing seasons, as well as adapting to competition from new species.  The species that has made the most notable living-tree biomass gains during this period is the Western redcedar, as it gained approximately 4.2% additional biomass over the period of study.

Another tree that was expected to thrive with the changing climate conditions was the western hemlock.  One of the most abundant trees in Pacific Northwest temperate rain forests, the stands in Southern Alaska are quickly becoming threatened by the expanding range of dwarf mistletoe.  This species of mistletoe is a parasite that affects many conifer species across North American forests by taking water and nutrients from their hosts.  Using climate envelope analysis, the Forest Service has predicted a growth in dwarf mistletoe habitat over the next 100 by a staggering 375-750%, which would offset any potential western hemlock habitat increases by a large margin.

With change on the horizon, the management of these forests will be important for numerous reasons.  As the climate slowly gets warmer, these temperate rain forests will become more productive in terms of live biomass, making such areas incredibly useful in terms of carbon sequestration.  It will also be important to consider how to slow the spread of dwarf mistletoe, as it has the ability to decrease the abilities of numerous tree species in these forests in terms of growth and vitality.  As our climate warms, it can be expected that temperate rain forests such as these will be counted on to adapt and continue to grow to allow for the additional carbon sequestration that might be lost in tropical zones.