Evolution of Australian Flora Flashcards
Vegetation classification
Instead of comparing species compositions of different rainforests, we classify the species into types of plants so that when we manage them, we can make sure we have representatives from all categories.
We assume that when a category is thriving, so are the correlated organisms so classification is the key to conservation and management.
What do we mean by Life form?
A fundamental life history strategy
Examples: Large herb, shrub, tree, small herb, lichen
What is physiognomy?
Plant community attributes:
Life forms and their architecture
The leaf area index (canopy open or dense, woodland or forest)
Phenology (seasonally dry, deciduous or evergreen forest)
Describing the Species pattern of plant communities
Plant community as attributes
1) Vertical structure (trees and vines in the top, palms in subcanopy, grassy understory etc)
2) horizontal structure
Describing Species composition of a plant community
Plan community attributes
Frequency of occurrence within a known area (figuring out what the dominant species are, transects or quadrats)
Cover (used for species that don’t allow you to count individuals, estimates of canopy cover = done by remote sensing)
Basal area (measure of tree diameter at 1.3 m ~breast height, how much timber you could get from an area in breast height)
Density (frequency by area)
Importance (“in this area which species seems to be the most important?”, Estimated based on size of species, or how frequently it is encountered)
Physiognomy defined
Combination of external appearance of vegetation, vertical structure the life forms or growth forms of the dominant taxa.
An emergent trait of the community.
Plant life forms includes traits such as
Size Shape Life span Degree of woodiness Degree of independence General growth habit Position of apical buds Leaf morphology Phenology
Raunkiær made a system of plant life form classification based on
Adaptation for surviving the unfavourable season (winter cold, summer drought)
Focused on the placement and protection of the apical meristems (the buds 💚)
Classification categories of plants in tropical rainforest
A. Autotrophic plants (chlorophyll)
1. Mechanically independent plants
a. Trees, shrubs or treelets
b. Herbs
2. Mechanically dependent plants (Structural parasites)
a. Climbers (vines - succulent- and lianas - big, woody climbing plants)
b. Epiphytes (orchids, ferns)
c. Hemi-epiphytes (figs, seeds in the canopy germinates and roots work their way down to the soil)
B. Heterotrophic plants (without chlorophyll)
1. Saprophytes 2. Parasites
Limitations of the rainforest
(Generally) Not water limited
Can be nutrient limited
Absolutely light limited
What does the first level of branching tell you in a rainforest?
Disturbance in the last fifty years. Low first level of branching tells you that there has been lateral light, and there should not be lateral light in a rainforest. Only directly above.
Bark in rainforests
Thin, not adapted to fire.
Branching in rainforests
Large fruit in the tropics, therefore less branching than in Europe for instance, fruits hanging closer to trunk and even on the trunk.
Buttressing - Buttress roots
Distinctive feature of tropical forests.
Extended support structure at the base of trees.
An outgrowth of the lateral roots. Common in emergent trees, rare in small trees
Increases with age, high rainfall and low elevation
Makes up for the fact that there is no deep rooting in rainforest trees. Most roots are in the first 50 cm to 1 m.
Ground herbs
Understory plants
Shade preferring
Families: zingiberaceae (gingers), cyperaceae (sedges), marantaceae, heliconiaceae. Abundant in wet areas.
Grass is an indicator of a disturbed canopy in rainforests.
