I is for

[rich59]

Imagination (thinking about woods, or seeing the end result of flint knapping when starting out with a piece of stone)
Ink cap mushrooms
Ice and the infamous ice lens

 

[jdlenton]

Ignition

Igloo

Inuit

Indian (red)

brain not working got to stop

 

[Tony]

Interest
Insects
Ireland
Iron
Illness
Incisor
Ink
Insulation
Irrigation
iris
Ivy
Invertebrates
Italian hitch
Ice Fishing

 

[Friar Tuck]

Icicle.....natures own lollypop
Illumination.....to see more
Incense....the smell of freshly cut oak
Infuse....make a brew
Inedible.....worm stew

John

 

[rich59]

Isthmus - land bridge
Inonotus obliquus - the true tinder fungus, chaga
imp - see "elf"
inch - about the length of the tip of my index finger and a useful measure
indigo - an ancient vegetable die (dark blue), possibly used in the earliest known human civilization - the Indus valley http://www.plantcultures.org.uk/plants/indigo_history.html

 

[rich59]

Iceman - Otzi - primitive man found in glacier with all his kit including tinder fungus, bow and much more. See http://www.mummytombs.com/mummylocator/featured/otzi.htm
Iceland

Itch - many sorts on camp, but I prefer the travelling one

Immense - the size of the planet to explore

Island - especially the deserted sort

Ilkley Moor (without hat)

 

[leon-1]

Igneous as in rock.
Ingenious as solutions to problems in the field.
Incandescence as in the natural incandescence of some fungi.
Itteration one of many cycles.
Impedance that which effects electricity and radio signals.