Plant Succession Along the Lemon Creek Trail
Mo Michels, University of Alaska Southeast
In our first daylong hike of the summer traverse, we JIRPers experience a transition of plant succession that in other places may spread across entire regions. What may take days to traverse in other parts of the world we hike through in a matter of hours, traveling from where coastal estuaries meet the ocean through mature forests, on through young forest, up into the wet vertical swampy stands that in turn bring us to tree line, and on and on into alpine meadows and only recently vegetated landscape of lichen and mosses. The uniqueness of this journey through time is due in part to the landscape of Southeast Alaska. Magnificent moving masses of ice excavated the landscape not long ago in the geologic past. Moving away from the coastline fjords and channels that harbor coastal towns, the ice crept back into the mountains leaving in its wake a succession of plant life. With the hike that JIRPers take up the Lemon Creek Trail to approach Camp 17 we were fortunate enough to see an abbreviated history of this process within a span of mere hours.
Driving to the trailhead was truly the beginning of this journey. Looking out the windows of the van, we saw a tidal estuary full of ducks, tideland plants, and grasses.
Having arrived at the trailhead, we marched through older and established coastal temperate rainforest. The over story of Sitka Spruce and Hemlock loomed above us, their towering trunks reaching over a hundred feet into the sky. The canopy filtered out the majority of the light, but Devil’s Club and other mid layer plants intermingled with the giants. In the gaps left by the fallen trees, the underbrush prospered, reaching up from mother logs to take advantage of these small breaks in the otherwise shading canopy. Passing through the mature forest, we made our way along a section of the riparian zone next to Lemon Creek. Here we went through a stand of alders, much younger and more uniform in diameter and spacing, their branches ending all around the same height and a layer of moss coating the smooth bark of their trunks. The only other obvious foliage were hemlock seedlings interspersed among the alders. In time, as this forest matures, the hemlocks may grow and dominate the upper canopy, shading out the alders.
As we left the riverbank, we skirted the edges of an active gravel quarry. The alien presence of trucks and heavy equipment was unavoidable and the anthropogenic influences on the morphology of the river were apparent where we walked. The edges of the stream were barren, recently excavated and flattened, and there was a manufactured hillside that was green with some recently sprayed fertilizing agent.
Crossing back out of the riparian zone, we passed through the mature forest before our journey took us into an area of wet soil pockets and swampy ground. Here the sedges, orchids and skunk cabbage prospered. This part of the trail went up for a couple kilometers before flattening briefly into meadows spotted with muskeg ponds and mud pits. All kinds of blueberry bushes flourished along the edges of the trail, heavy with fat juicy berries. Only after picking a few hundred did we began to notice the subtle differences between the two species, the blue and red huckleberries.
We traveled onward, delayed by berry picking only long enough to wish we had a bucket to save them. Each bush we passed taunted us with its burden, until we finally found ourselves leaving tree line to enter an alpine meadow. The tall trunks of spruce and hemlock and the trill of birds were replaced by the buzzing of fat bumblebees as they flitted between grasses to wild geranium, to alpine lupine, to dwarf fireweed.
As we hiked ever higher, the greenery changed once more. This time the darker green of mosses and lichens replaced the lighter green alpine grasses. These mosses and lichens mark the first succession of plant life onto a glacially carved landscape. Small primary successional plants break down rock, adding limiting nutrients like nitrogen to the ecologic system and allowing for later successional plants like the ones in the alpine meadow to come in and take root.
Eventually, as we climbed even higher, this low lying, hardy, vegetation gave way in some places to exposed, barren rock, and then to actual ice. At this point Camp 17 emerged from the clouds and the Lemon Creek and Ptarmigan Glaciers marked the end of successional vegetation changes. As the glaciers continue their retreat and the ice melts away to expose more bare rock, the lichens and mosses will begin to take hold and continue the upward march of plant life towards the ridge line.