Maple Watch Science
Maple Watch began with my masters degree study at UNH. I wanted to take the pulse of my sugar maples. If these trees, which have nurtured my family for 80 years, are in danger, I want to know when and how they show the first damage. I told Dr. Barrett Rock, my advisor at UNH, that I wanted to take the temperature of my trees. Like any mother, monitoring her child's health, I don't want to wait until the trees have a fever of 104o F. I want to know when my trees show that first feverish sweat.
I also wanted to monitor my maples with very simple tools. How do the leaves look? Are the buds fat and viable? Is the fall foliage color a peak? I set up a study on five different sugarbushes in and near the Bearcamp Valley where I live. I tagged 30 trees for study. During the 2008 growing season, I collected leaves each month. Using a spectrophotometer in Dr. Rock's lab, I measured leaves for chlorophyll content, water content and maturity.
The summer of 2008 proved typical of the climate change summers scientists project we will soon notice. In late April, just as mouse ear leaves opened on the maples, my community experienced the longest dryest spring on record, no rain until late June. Then the rains came down in deluges for six weeks, turning my gardens into a slough of mud.
All trees in the study showed water stress early in the growing season. That stress grew worse, even when rain returned in late June. All trees also showed loss of chlorophyll. Most trees showed a decline in leaf size--the trees abscissed or cut off large expensive leaves to save smaller leaves and the buds those leaves protected. In the fall, all but 6 trees dropped their foliage in mid-September or earlier. The fall foliage was a dismal wash of pale, spotted leaves that never reached full color. Despite these signs of stress, almost all of the trees produced healthy viable buds. The maples were making biochemical choices, putting energy and sugar on bud production for the coming year.
That choice as to where to put limited sugar appears to be a widescale trend for sugar maples. Throughout the region, historic records of sugar production indicate that the sugar maple is becoming less sugary. In my research of old agricultural records and sugarmaker journals, I found that average sugar content has fallen steadily from 3-3.5% in the 1950s to 2% or less today.
For sugar producers, less sweet sap means longer boiling time and more sap. It took 30 gallons of sap to produce one gallon of syrup in the 1950s. Today, less sweet sap means producers need 50-70 gallons of sap for make one gallon of syrup.
For the tree, such a change means less sugar for building wood, growing large leafy canopies, producing buds and managing a biochemical system that can repeal insects, deal with acid rain and withstand more hot summer days. Sugar is health for the maple.
By the end of October 2008, I thought my masters thesis was done.
In March 2009, Rudy and I tapped our sugar maples. The first run of sap usually produces light amber syrup, a golden champagne of syrups. This year, our first draw of syrup was dark. The filters were clogged with gooey black nitre. "My trees are acting like their wounded," I thought.
More research is needed. I applied to continue the project as a PhD candidate. I was accepted to the UNH Natural Resources and Earth Systems Science program.
In the summer of 2009, a dozen members of the New Hampshire Maple Producers Association volunteered to help Maple Watch collect sap samples every day when sap runs during the 2010 sugar season. All of them had dark and darker syrup in 2009. They want to know what's happening to their trees.
As the assays of sap are made, I will look for patterns, trying to identify what we're seeing. Later when leaves open, I will collect leaves from each of the participating sugar bushes, scanning leaves for measures of chlorophyll, water and maturity. Late in the fall, we will examine buds to assess their viability for the following year.
As we proceed, I will map each sugarbush and then look at satellite images of New Hampshire to see if we can "see" the same sites from 500 miles in space. If we can, the Landsat images captured in space will provide us with the same information we get from the light reflected in the laboratory spectrophotometer, measures of chlorophyll, water and growth in the treetop canopy. Our ultimate goal is to monitor the health of the sugar maples throughout its 36 million acre range.
This page will present the protocols which sugar makers will follow this year. As we proceed, we will report our findings.
Time, equipment and funding will not support more sampling this year. But if you are a sugarmaker and would like to participate, let us know. In 2011 and 2012, if funding can be found, we dream of expanding Maple Watch assays of sap and leaf samplings throughout New England and into the entire maple range. Very simple observations of syrup grade and color, leaf development and bud health might help guide us as we expand the study. Ground truthing on sugar maple sites will be needed across the maple range.
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