Summer on a Shoestring

Playing God by Rebecca Walling
June 6, 2011, 10:29 am
Filed under: Fertilization

This week we jumped into fertilization.  My boyfriend Craig joined Ruth Yanai’s lab, and a month later I am in the middle of the White Mountains of New Hampshire ducking under saplings and climbing over granite boulders to spread phosphorus and nitrogen on the forest floor.

Last week, we picked up 300 lbs of ammonium nitrate and a half-ton of monosodium phosphate. Corrie and Craig worked out a measuring scheme to divide the nutrients into sandwich bags for spreading across each plot. We have 13 stands to subject to our treatment.  At each stand, we have four plots: one control (no fertilization), one nitrate addition, one phosphate addition, and one nitrate + phosphate addition. Another crew worked out a system to divide each plot into its 9 interior subplots, and subsequently divide each subplot into 4 rows.  Add in a 10 m buffer (divided into 16 buffer subplots), and you have a total of 650 bags of nitrate and 650 bags of phosphate.

The biggest challenge this week was deciding how to distribute the nutrients evenly over the forest floor.  The nitrate is pelletized into little “prills”, making it easier to spread.  It looks, for lack of a better analogy, like dippin’ dots – those overpriced “futuristic” cups of ice cream sold at theme parks.  Think of the challenge this way: we need to spread a cup of dippin’ dots over a 10 m x 10 m area.  That works out to about 7 dippin’ dots in an area the size of a dinner plate.  Tricky, but doable with practice.

Ammonium Nitrate dancing inside a bag

Spreading the phosphate presented a more difficult challenge.  It is a powder – about the same consistency as powdered sugar.  Imagine having to coat a donut that is about 11 m in diameter with half a cup of powdered sugar.  This metaphorical donut, of course, is pocked with large boulders, fallen trees, and is on a 30 degree slope up a mountain.  We thought of using a flour sifter.  Then a salt shaker.  Corrie saved the day by taking urine sample cups (presumably unused), cutting little circles of mesh screen, and using a rubber band to fasten the screens to the cups.

Monosodium Phosphate in a shaker

For the last two weeks, we have been perfecting our methodology.  A crew of 3 arrives at the field site.  Everyone walks up and down 2.5 m wide lanes in the control plot, making sure to impact the surface in the same way that our experimental plots are impacted.  The whole crew moves to the nitrogen plot.  Two people begin laying 10 m ropes out, marking each fertilization lane. A third person divides each bag of nitrogen into quarters.  We do the same thing nine times – move ropes, measure fertilizer, spread fertilizer, start again.  Once the interior of the plot has been fertilized, we move to the buffer zone.  Since the buffer need not be as precise as the measurement zone, we can spread an entire bag of fertilizer over one square, without subdividing it.  As I understand it, the reason we fertilize the buffer is that a large component of this study involves looking at tree response to fertilization.  Trees have root systems that can stretch beyond the measurement zone.  If they are on the edge of the plot, they take nutrients from not only the measurement zone, but also may draw nutrients from soil in the buffer zone.

Equipment in the field for measuring subplots and spreading fertilizer

And so the day goes – we finish the nitrogen plot, and move to the phosphorus plot.  We finish the phosphorus plot and move to the nitrogen + phosphorus plot.  Where we begin the whole process again: lay ropes, measure fertilizer, spread fertilizer.  It’s exhausting, mind-numbing work, tramping through the woods and spreading prills and powders. As tiresome as fertilization is, I can’t wait to hear about the results that come out of this research.  Nutrient addition is, in a way, the ultimate field manipulation.  As Ruth Yanai pointed out, it’s kind of like we’re playing God.  What could be more God-like to an ecosystems ecologist, after all, than altering the nutrient composition of the soil?

The first sprinkle of fertilizer is applied to a shoestring site by Ruth Yanai, after many years of preparation!



The fertilization countdown: 9 down, 4 to go.


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I have been absent for some time, but now I remember why I used to love this site. Thanks , I’ll try and check back more often. How frequently you update your web site?

Comment by Duane Cuomo

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