abstract
background
bare
bark
black
branch
collection
color
colorful
coniferous
crown
deciduous
design
drawing
ecology
element
environment
evergreen
fir
fire
forest
graphic
green
icon
illustration
isolated
leave
natural
nature
oak
outdoor
outline
pine
plant
root
rootage
set
shape
silhouette
spruce
stem
system
trace
tree
trees
trunk
white
wood
wooden