Subject
Trees
Forests and forestry
48
Shrubs
32
Forest ecology
30
History
24
Diseases and pests
23
Ecology
19
Environmental aspects
18
Plants
18
Symbolic aspects
15
Identification
13
Growth
12
Religious aspects
12
Ecophysiology
11
Climatic changes
10
Tree planting
10
Botany
9
Social aspects
9
Woody plants
9
Breeding
8
Effect of air pollution on
8
Ornamental trees
8
Wood
8
Wounds and injuries
8
Arboles
7
Forest genetics
7
Forest management
7
Timber
7
Arboriculture
6
Biotechnology
6
Gardening
6
Genetics
6
Growth (Plants)
6
Human-plant relationships
6
Climatic factors
5
Folklore
5
Human ecology
5
Physiology
5
Planta
5
Therapeutic use
5
Adaptation
4
Effect of atmospheric carbon dioxide on
4
Forest insects
4
Historic trees
4
Landscape assessment
4
Nature, Healing power of
4
Psychological aspects
4
Trees in art
4
Trees in cities
4
Trees in literature
4
more ...