Tuesday, 5 July 2011

SALCA Field Trip day 2

The conditions outside are looking considerably less bright than yesterday, so we head into Chester to collect equipment for experiments we are planning this week.
SALCA at plot 13 (open deciduous)

As we have decided not to scan this morning, we decide to start the manual field data collection, of plots 2 and 3, which include GPS positioning of the plots and tree measurements such as height (using a clinometer), diameter breast height and species composition, which could be important considering possibile variability of bark and leaf reflectances.
Plot 14 (Dense deciduous)

The afternoon  brightens up and two deciduous sites are chosen for scanning. The first (plot 13) is near a picnic area and has been chosen as it is a relatively open stand, with large, but dispersed sweet chestnut trees. The second stand chosen (plot 14) is a much denser stand composed of a greater variety of deciduous trees including sweet chestnut, birch, rowan, oak and wild cherry.
Moisture experiment setup. As SALCA is an active laser sensor, scanning in the dark is fine!

Whilst at plot 14, we also collect a selection of dead and live sweet chestnut leaves for further experiments back at the cottage. The wavelengths used by SALCA have the potential to provide a useful index of vegetation moisture content, as high leaf moisture will result in high absorption at 1550 nm. In constrast, the 1040 nm laser will mainly be sensitive to structural characteristics of the leaf. The experiments are the first test of the sensitivity of SALCA to vegetation health and leaf moisture content. A live leaf, a dead leaf from the forest litter layer and a partially oven-dried leaf are scanned at high resolution in both wavelengths to compare the intensity of the return signal. A ratio of the two wavelengths could provide an early indicator and useful measure of vegetation stress, drought and disease in woodland as well as estimates of forest fuel moisture content, a significant factor in determining fire risk. Early results look promising and future experiments will look to quantify the relationships between moisture content and SALCA intensity - check back soon for more results!

Oliver Gunawan & Rachel Gaulton
5th July 2011

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