Science for Everyone



new needle growth, and immature female seed cones on a white spruce bough

Male pollen cones from a white spruce

Immature female seed cones on a white spruce

pollen sometimes blows out onto the ocean

While I was working in the lab on Hurricane this past week, I spied a beautiful little Northern Parula (Setophaga americana) foraging and darting in between the bough's of a nearby White Spruce (Picea glauca) tree. Every time the warbler emerged, it was followed by a cloud of yellow pollen. While many of the flowering plants (angiosperms) on Hurricane Island have yet to bloom, this is the season where conifers or evergreens (gymnosperms) are releasing pollen, and dusting everything in sight. 

Hurricane Island has three conifers that dominate the landscape: red spruce, white spruce, and balsam fir. At first glance, all of these evergreens might be hard to tell apart. I always remember the difference with the following mnemonic:  the "sharp, square, spruce" and the "flat, friendly, fir." Spruce tree needles are square and can be rolled across the palm of your hand, but fir needles have just two sides. Spruce needles are also shorter and tend to grow forward from the stem rather than perpendicular to the stem like balsam fir, which means that if you give a spruce tree a handshake it feels a lot more prickly or sharp. The other major difference between spruce and fir trees is that spruce cones grow up from the branches and fir cones grow down from the branches. 

But back to the pollen. For a very short period of time, the evergreens on Hurricane form a different cone in addition to the large, scaly, female seed cones that you are probably familiar with. Male pollen cones are much smaller (just about 1/2 inch long), and last for just a few days. Their purpose is to release pollen and fertilize the female seed cones before they fall off the tree. 

Along with releasing pollen, Hurricane's evergreens are also in the process of developing new needles which form on the tips of each branch and stay a lighter green color well into summer. After this flurry of activity in the spring, the conifers will not be changing much except for the newly fertilized female seed cones. These will continue to grow and develop for several years before releasing the seeds. 

One part of the research that we do on Hurricane is to monitor the phenology, or timing, of life cycle events in the plants and birds on the island. We use Nature's Notebook to record data on when events like new needle growth and the presence of pollen cones happen to the conifers on the island so that we can compare the timing of these events to other parts of Maine or the US. Other scientists can also create scientific models from these data to predict the impacts of climate change on the timing of when these events happen, which can also help us understand other things like changes in Maine's growing season.

Take a look around you at your home! Notice any new things blooming or growing? Have the conifers already released their pollen? 

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Forest Health Assessment Results

Post by Chloe Tremper, Science and Education Intern 2014

Throughout this past summer, I have gotten to know the forests of Hurricane very well, particularly the spruce-fir stand on the northern half of the island along Slocum’s Trail.  Red spruce (Picea rubens) is by far the most dominant species on the island but is generally only found in the interior the spruce-fir stand on the island.  White spruce (Picea glauca) lines the edges of the stand along trails and the coast but is completely absent from the interior of the stand.  This reflects the white spruces near inability to survive in suppressed conditions and reproduce in closed canopy conditions.  Balsam fir (Abies balsamea) is the last species of tree I found within my study area and the least abundant.  However, when it was found it was generally in plots near the coast and it was always found in concentrated groups.

 Hurricane Island Foundation 
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   Coring a red spruce to count growth rings to estimate age

Coring a red spruce to count growth rings to estimate age

Very few of the trees within my sampling area had reached their full growth potential, despite some of them being well over one hundred years old.  This can mostly be attributed to having grown in a less than favorable environment with high competition for very limited resources among individual trees.  Hurricane’s climate (particularly its regular inundation of ocean fog) and shallow, acidic soils are two factors making the island a harsh environment for the trees to survive in. 

Overall, Hurricane’s spruce-fir stand is doing pretty well.  Fire is the biggest risk currently facing Hurricane’s forest due to the massive amount of dead woody debris on the forest floor and the fact that spruce needles are extremely flammable.  The possibility of windthrow (when trees are uprooted by wind) is also fairly high due to the shallow soils and the naturally shallow rooting systems of spruce and fir trees. There is also the potential for an infestation of witches’ broom (a dense mass of shoots growing from a single point off a tree caused by variety of things – generally fungi or a virus) as it is already present on some of the spruce trees along the eastern coast of the island. 

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Forest Health Assessment of Hurricane Island

Post by Chloe Tremper, Science and Research Intern, Project Update 

For my summer research project, I am completing a forest health assessment of the spruce-fir stand on the northern half of Hurricane Island.  Forest health and how to assess it is hugely subjective depending on the forest type you’re working with and what your definition of “healthy” is.  For this particular assessment I decided to focus on damage and disease within the forest, regeneration, blow down risk, and fire risk.  Since little is known about Hurricane’s forests, my project aims to determine any major risks currently facing the spruce-fir stand on the island as well as recommend any needed management and improved methods of monitoring the overall forest health into the future.

In order to complete this assessment in a few short weeks by myself, I decided to collect data at 12 plots within the spruce-fir stand.  Using Slocum’s Trail as the base of my 600m transect, I used a random number generator to determine 12 random distances between 0 and 600m.  After each of these distances were measured out and flagged, the real fun began! At each distance in from the start of the transect, I start by flipping a coin to determine if the plot will be on the left or right side of the trail: heads means right and tails means left.  After that, I roll a di to determine the distance into the stand I go from Slocum’s (1=5m, 2=25m, 3=50m, 4=75m, 5=100m, 6=150m).

Chloe enters data with ISLE botany students recording DBH for white and red spruce trees in a plot

Chloe enters data with ISLE botany students recording DBH for white and red spruce trees in a plot

Once at each plot center, I set up a 5x5m square plot.  Within that plot I record the species, DBH (diameter at breast height), and signs of damage/disease for each tree.  I am also recording the number of 1-hour, 10-hour, 100-hour, and 1000-hour fuels. 1-hr fuels are debris less than 1/4in diameter (twigs, needles, dead grass), 10-hr are woody debris 1/4 – 1in in diameter, 100-hr are woody debris 1 - 3in in diameter, and 1,000-hr are woody debris greater than 3in in diameter. These numbers are important for estimating the risk of a fire within the stand as well as how much potential damage a fire would cause.  I also tally the number of spruce saplings, fir saplings, Vaccinium spp., and other woody saplings or shrubs in order to get an idea of what would likely take over a plot if the large trees were to die back.  Once all these data are recorded, I measure the soil depth in the northwest corner of each plot.  Knowing the soil depth is helpful in considering the risk of blow-downs. 

I am taking notes about each plot including information about the openness of the canopy, exposed bedrock, fallen trees, herbaceous cover, etc.  So far, I have 8 of the 12 plots completed.  I finished 3 of these plots with help from our SLE Botany students! Of the plots I have completed, I’ve noticed a lot of diversity among them, however the one thing I have seen throughout is a lot of dead woody debris which puts the island at a huge risk if there were to ever be a fire on the island.  Remember, only you can prevent forest fires! 

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