Lecture4 1 interception and ET dung

Rainfall Interception Vegetation often modifies the intensity and distribution of precipitation falling on and through its leaves and woody structures Interception is the water retaine

Rainfall Interception

Vegetation often modifies the intensity and distribution of precipitation falling on and through its leaves and woody

structures

Interception is the water retained on plant

surfaces during and after precipitation

Interception: Ic = Pg – Th – Sf

Importance of interception

Canopy Interception (Ic) Total Precipitation (Pg) Throughfall (Th)

Stem flow (Sf)

Throughfall

Point measurement

Spatially averaged measurement

Interception, throughfall and stem flow

Canopy Interception in Japan

Type of Forest Annual

Rain (mm)

Canopy Interception (mm)

% of interception

Reference

Red Pine 1024.4 198.5 19.4 Murai (1970) Japanese Cypress 1793.0 457.8 25.5 Iwastubo (1976) Japanese Cypress 1542.5 328.9 21.3 Hattori (1982) Japanese Cedar 1621.6 378.3 23.3 Tange (1982) Japanese Cedar 1702.7 245.3 14.4 Tange (1982) Deciduous forest 1793.3 360.4 20.1 Iwatsubo (1967)

Why so much variation???

Controls on interception losses and

•Energy Availability (Solar Radiation)

•Position of under tree canopy

• Conifer forests in North America Ic = 15-40% of Pg

• Natural teak forests in Thailand Ic = 65% of Pg

Amount of Rainfall Interception

Throughfall over one storm

1:1 line (no interception)

= P gross

Pnet