A late-night disco in the forest reveals tree performance

A late-night disco in the forest reveals tree performance
Research structure at Hyytiälä, Finland. Credit: University of Helsinki

In 2017, the group from the Optics of Photosynthesis Lab (OPL) developed a new method to measure a small but important signal produced by all plants, and in this case trees. This signal is called chlorophyll fluorescence and it is an emission of radiation at the visible and near-infrared wavelengths. Chlorophyll fluorescence relates to photosynthesis and the health status of plants, and it can be measured from a distance, for example from towers, drones, aircraft and satellites. Interpretation of the signal is, however, complicated, and so far it has only been possible to measure it within discrete spectral bands from fully-grown trees in the field.

OPL devised a that, for the first time, allowed them to observe from a distance the full spectrum (all colours) of of mature trees growing in the . Measuring the whole spectrum of emission reveals information on both plant performance (how they photosynthesise) and the structure of the plants themselves.

The issue with conventional remote sensing methods used so far has been that during daytime, most of the fluorescence distribution remains hidden from view, as the signal is so weak compared to sunlight. Therefore measuring fluorescence during daytime, commonly referred to as Solar-Induced Fluorescence (SIF), requires extremely sensitive and specialised instrumentation. The new technique differs from these previous efforts by using commercially available LED technology, which literately lights up the forest at night to reveal the full spectrum of emission of whole trees.

"We realised we could use the night as a 'natural filter," so we went into the forest at night and attached a strong wavelength-restricted (a commercial disco-type light) to a tower that excited the fluorescence. Next, we used specialist scientific instrumentation, a spectroradiometer, also mounted in the tower to observe the signal," describes Jon Atherton, researcher from the University of Helsinki Optics of Photosynthesis Lab at the Institute for Atmospheric and Earth System Research (INAR) / Forest Sciences of the University of Helsinki.

Combining night and light simplifies things: measuring SIF at night can be done with potentially cheaper (less sensitive) instruments and it provides data that is easier to interpret.

The link between fluorescence and terrestrial carbon sinks

The researchers' new contribution puts us one step closer to "observing photosynthesis" by looking at the light emitted by plants, both on smaller scales (greenhouse, crops, forest stand) but also globally using satellites. The European Space Agency is preparing the FLEX satellite mission, which aims to map fluorescence globally. The hope is that fluorescence will be used to routinely estimate plant photosynthesis from space, which is the process that drives the terrestrial carbon cycle.

The role of forests in the uptake and assimilation of atmospheric carbon is crucial and widely discussed in the media. Measuring the exchange of carbon dioxide between forests and the atmosphere is accomplished with expensive instrumentation in specific places (flux tower sites) which produce localised estimates of fluxes (carbon exchange) close to the sites. This is where fluorescence enters into play by providing a remote-sensing-friendly means of estimating photosynthesis across the landscape by filling in the coverage (gaps) between the stations. Interpreting the data is challenging, but with the Light Emitting Diode Induced Fluorescence (LEDIF) technique there should be a significant leap forward.

"It is the potential for measuring fluorescence from space that really motivated us to do this work, although our results could have other applications too such as phenotyping, precision farming or forest nurseries. We hope that our data can be used to inform algorithms used to 'retrieve' fluorescence from space. Such algorithms work in a slightly different way to our spectral technique as they exploit dark atmospheric 'lines' to estimate fluorescence. Hence, the full emission spectrum remains effectively hidden in satellite data, and that is what our data reveals," Jon Atherton adds.

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May 14, 2019
I read somewhere a couple decades ago that a saline dipped string around I think it was a capacitor was used as a probe to listen / see tree biorhythms on an oscilloscope

I always wanted to place this type of probe technology throughout an area of trees and watch the biodynamic Exchange of the forest "eavesdropping & tapping"

I have noticed trees have there own sonic signature like a car engine or an aerolpane
because of the noise induced by the aerodynamics of the philotaxis and leaf shape.

trees sound different . I believe this noise is not only interesting but it may be a vital part of their consciouses .

I once fell into a trance and saw them as stationary lightning

another time I was in trance the tree was like a cosmic antenna showing me all sorts of different

I think this is why megalithic people put said trees into the ground in geometries to act as portals / thresholds

May 14, 2019
lidar maps will reveal underground water
because tree trunks bifurcate above water running under them
and the true meaning of the v sign

controversial as it may seem tulleric (earth energy dowsers)
often cure a great deal of human pathologies

I know personally of a friend who had fatigue syndrome sleeping sickness m.e.
and the dowser just asked him to move his bed a few feet and he soon recovered

this radiation I can't understand but it may be of similar properties to those of
doping semiconductors to induce quantum strangeness but now I'm just guessing

Lidar is a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representations of the target.

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