The parameters measured in the field were Basal Area (BA)[i] of live, and dead standing, trees and shrubs with BHD > 10cm; Presence/Absence Of Species and of Saplings and Poles (bhd <10cm, or too thin to count in the BA assessment but within the 20m radius of the site), Height Classes for trees and shrubs[ii], Densitometric of canopy cover[iii], Understory Relative Abundance[iv] and Stand Structure (single-, double- or multi- storeyed, and the presence of shelterwood). See Appendix A for copies of the field forms used in this study.
Stem Density was estimated from standard site images according to the following protocol. Broad view images in the four cardinal directions were captured at each way point site using either a Sony Alpha 700 fitted with a Minolta 20mm AF lens, or a Lumix … fitted with a 28mm wide lens. The actual area covered by the four cardinal images of the estimated 314 m2 corresponding to the area encircles by a 10m radius circle was calculated based on the angle of view of the lenses used. A 0.69 cover factor (216 m2) was calculated for the Minolta lens and a 0.61 ((192 m2) for the Lumix lens. Calibration pictures were taken in situ to establish the position, in the images, of a 10m depth when the images were taken under normal field shooting conditions. Tree trunks of various diameters classes (see Table 2), located between the front and the 10m depth line of the image, were counted for each of the cardinal views and added for each class. This information was then used to determine the stem density for each DBH class.
|dbh (cm) class||code|
|2.5 to 5||1|
|7.5 to 12.5||2|
|15 to 20||3|
|25 to 35||4|
[i]. University of Minnesota Extension service. 1998. Forest Management Practices Fact Sheet Managing Water Series # 12: Making and Using Measurement ToolsCBasal Area. Publication FS‑06981 (http://www.extension.umn.edu/distribution/naturalresources/DD6981.html)
[ii]. Measured using a …. ranger.
[iii]. Determined from canopy photographs. Conversion of image to 8bit gray image, thresholding to an 8bit black&white, and determine % canopy cover from the black pixel count to total pixel count.
[iv]. Determined in situ and through standard photographs of the site using ….