Upper Canopy Assessment

ESRM 304

Forest Measurement

• Two strata are defined for measurement convenience / efficiency – Lower canopy –understory, groundstory, woody detritus • Component from which secondary forest products derived • Composition, constitution, spatial arrangement, density • Exotic / Invasive species status • Wildlife habitat for many creatures depends on structure • Water yield: surface flow, erosion, percolation, etc. – Upper canopy – sometimes called overstory vegetation • Component from which primary forest products derived • Composition, constitution, spatial arrangement, density • Wildlife habitat for many creatures depends on structure • Recreation potential and aesthetics • Water yield: interception, throughfall, stemflow, etc.

1 Forest Measurement

• Individual tree measurement forms the basis for all forest assessment / inventory • Many relationships can be derived from individual tree attributes – Species – Diameter – Height – Crown – Age • Direct measurement, sampling, prediction are all involved

Individual Tree Measurement

• Diameter – Most frequently measured diameter is Diameter Breast Height, or, DBH for short – Average stem diameter (in inches!) outside bark of the tree measured at breast height above ground level • In U.S., breast height is taken to be 4.5 ft. • On steep slopes measure on the uphill side of tree • Leaning trees require measurement along the bole • Trees forking below breast height are treated as two • Trees forking above breast height – avoid swells • Other stem deformities – move above it

2 DBH

Diameter Measurement

• Instruments (Dendrometers) – Diameter tape (D-tape) is most common • accurate to 0.1” (in U.S. always measured in inches) • two graduated scales: ordinary inches and diameter equivalents • most consistent method • slight positive bias – Calipers • accurate to 0.1” • tends to give different estimates around bole • ideal for small to mid-sized trees • take two measurements on decidedly elliptical stems – Biltmore stick • suffers all same problems as the caliper, only more so • accurate to ½ inch

3 Diameter Measurement

• Diameter classes – Very often expedient to summarize inventory data into size classes based on DBH – No matter the size of class used – still measure to 0.1” ! – 1-inch classes • 2” class (1.6 to 2.5”), 3” class (2.6 to 3.5), … – 2-inch classes • 4” class (3.1 to 5.0”), 6” class (5.1 to 7.0), …

Diameter Measurement

• Diameter (size) distributions

4 Diameter Measurement

• Basal Area – Cross sectional area of the tree at breast height – assuming stem circularity – always in square feet! (in U.S.) – Area of circle, A = π r 2 – Basal area, g = π (DBH/2)2 (1/12)2 = 0.005454 DBH2 – Average stand DBH is a useful statistic for management – Quadratic Mean DBH (QMD) is the diameter of the tree corresponding to the tree of mean basal area

g QMD = Dg = 0.005454

Individual Tree Measurement

• Age – Trees in temperate zones grow one distinctive layer of wood per year so age is found by counting these annual rings • Care is needed to avoid counting ‘false’ rings – Tree Age: • Total Age: Elapsed time since germination of a seed or time since budding of a sprout or cutting • Breast-height age: Elapsed time since tree height exceeded breast height – Stand Age: • Plantation age: Elapsed time since planting – regardless of seedling age – Even-aged vs. Uneven-aged

5 Age Measurement

• Instrument – Increment borer Handle

Auger (bit)

Extractor (spoon)

Increment borer use

6 Increment borer use

Individual Tree Measurement

• Tree Height – Total height: distance from tree base to tip (volume, biomass, site quality) – Height-to-crown: distance from tree base to base of live crown – Merchantable height: Height to a minimum top diameter – Instruments are called “hypsometers” • Direct measurement: Height poles • Indirect measurement – Similar triangles – Trigonometric principles (clinometer)

7 T Height Measurement

Tree Height = DT + BD.

O D

DT/OD = tan(TOD), therefore, DT = OD x tan(TOD) B DB/OD = – tan(DOB), therefore, DB = – OD x tan(DOB),

Tree Height = OD x tan(TOD) + [– OD x tan(DOB)], or, Tree Height = OD x [tan(TOD) – tan(DOB)].

Horizontal distance OD is measured with a tape. Clino measures tangents of angles TOD, DOB in percent (100 x tan), so

Tree Height = OD x [TOD% / 100 – DOB% / 100], or Tree Height = OD / 100 x [TOD% – DOB%]

Slope correction for height measurement

O D

D’ OD/OD’ = cos(DOD’)

OD = OD’ x cos(DOD’)

Measure angle DOD’ with clinometer in degrees & plug into height equation:

Tree Height = [OD’ x cos(DOD’)] / 100 x [TOD% –DOB%]

8 Individual Tree Measurement

• Height in relation to age - Site Quality – Trees are resource integrators – Site Index: The average height of undamaged dominant trees at a reference age – Dominant tree height insensitive to crowding – Reference, or base, or index age chosen appropriately – Species dependent – Sometimes dominant trees are unavailable; challenge esp. in mixed stands – Requires trees on the site

Site Index

James King (1966) published site index curves for Douglas- fir in the Pacific Northwest

9 Permanent Sample Plot Layout

Large Tree measurement plot Small Tree measurement plot • 0.1 acre plot  37.2 foot radius • 0.025 acre plot  18.6 foot • white PVC pipe at plot center ; plot number radius written on it w/ indelible ink • same plot center as large plot • all trees within the plot have aluminum tags • trees are not tagged • first tree on plot marked with pink flagging • perimeter is not marked

10 Upper Canopy Surveys

• Field Trip to St. Edward State Park • Tue and Wed (4th & 5th) • Depart from behind Bloedel Hall (C-10 parking lot) promptly at 12:30 P.M. • Bring rain gear, sturdy footwear

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