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Floristics
Floristic surveys are concerned with an assessment of species composition
of vegetation, rather than the structure. These are favoured for
large-scale (small area) studies of a detailed botanical nature.
The information can be integrated for larger area studies, e.g.
vegetation classification and mapping. The identification
of species is essential for floristic mapping.
- Qualitative Floristic Description - presence/absence
Qualitative floristic measures document the actual species comprising
a community, rather than its physical structure. The simplest
floristic description of a vegetation type is simply a list of
the species present.
- Semi-quantitative and Quantitative Description - measures
of abundance
Often the species list is accompanied by a measure of abundance
of each species.
Measures of abundance include
These areas are detailed below.
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Please read
Your textbook
pages 111-138
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Identification
The importance of accurately identifying species is paramount
in surveys, as this is the primary unit of measurement.
The use of field guides and taxonomic keys are important components
of surveying flora. Many local field guides and keys are available.
The identification of specimens should be checked at your state
or territory herbarium, where voucher specimens should also be lodged.
Listed below are the some references and local field guides.
Brock J. (1988). Top End Native Plants. Reed, Chatswood
NSW.
Cowie I., Short P.S. & Ostercamp Madsen M. (2000). Floodplain
flora: a flora of the coastal floodplains of the Northern Territory,
Australia. Australian Biological Resources Study, Canberra.
Dunlop C., Leach G. & Cowie I (1995). Flora of the Darwin
region. Conservation Commission of the Northern Territory, Palmerston.
Kenneally K.F., Edinger D.C. & Willing T. (1996). Broome
and beyond: plants and people of the Dampier Peninsula, Kimberley
Western Australia. Western Australian Department of Conservation
& Land Management, Perth.
Simon B.K. & Latz P. (1994). A key to the grasses of the
Northern Territory. Northern Territory Botanical Bulletin No.17.
Conservation Commission of the NT, Palmerston
Smith N.M. (1995). Weeds of natural ecosystems: a field guide
to the weeds of the Northern Territory. Environment Centre of
the NT, Darwin.
Wheaton T. (1994). (editor). Plants of the Northern Rangelands.
NT Department of Lands, Housing and Local Government, Darwin.
Whightman G. (1989). Mangroves of the Northern Territory.
Conservation Commission of the Northern Territory, Palmerston.
Cover
Cover is the percentage area of the ground occupied by aerial parts
of a species when viewed from above. It includes basal area, canopy
cover, ground cover, and leaf area cover. Total cover of an area
may exceed 100% because of overlayering of species (stratification).
Various ways of measuring cover include
- visual estimates within quadrats - can be used to
rank the species in order of abundance (i.e. list the most abundant
species first, then the second most abundant species and so on)
- single cover pins (point quadrats)
- frames of pins or cross-wires.
Advantages
Adds information about relative abundance. Visual estimates
are fast compared to quantitative descriptions. Can be applied to
vegetation units of any extent. Good method to use where it is difficult
to know where one individual starts and another ends, e.g. grasslands.
Disadvantages
Visual estimates become more difficult as the size of the plant
increases. The precision of visual estimates varies widely from
person to person. Precision of estimates is not linear with cover.
Use of pins and frames is tedious and time-consuming.
Density
Density is the number of individuals of a species per unit area.
Advantages
It is accurate, allows direct comparison between different areas
and species, and is an absolute measure. For long lived perennial
species, measures remain relatively stable from year to year, such
that the method may be useful for baseline inventory.
Disadvantages
Less suitable for the herbaceous layer, especially when there are
numerous plants to count or identification of individuals is difficult
(e.g. many grasses and mosses). It is most often applied to larger
plants such as trees, shrubs and more prominent perennial forbs.
Can be tedious counting small or very dense individuals.
Frequency
Frequency is the probability of finding a species in a particular
area. It can be measured by taking a number of quadrats and recording
presence/absence in each, or in each of the sub-divisions of the
quadrat.
Advantages
Simple to measure as it only requires identification of the
species in each quadrat, not the number of each species. Useful
when individuals cannot be distinguished.
Disadvantages
Frequency is dependent on quadrat size, and the frequency obtained
reflects the pattern of distributions of the individuals as well
as their density. For example, if frequency declines over time,
it may be because individual plants are more sparsely scattered
over the entire area, or because the range of the species distribution
has constricted.
Biomass yield
Biomass yield is the fresh or dry weight of vegetation per unit
area (for all species or individuasl).
Advantage
This is an accurate and repeatable method.
Disadvantage
This is a destructive method. It is also labour intensive which
tends to result in a reduction of samples collected, and therefore
the representativeness of overall sampling strategy.
Basal Area
Basal area is the diameter of an individual plant at breast height
(dbh).
Advantages
This is an accurate and repeatable method which can give a measure
of potential forestry yield. Used for trees.
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For more information
Please view
Weblink
1. http://www.rfa.gov.au/rfa/
nsw/nsw_Eden/
Appendices 1 and 2 of the Regional Forests Agreement
provide details of two plot based floristic surveys.
"Compilation and Validation of State Forests Flora Data -
Eden CRA region" - a report undertaken for the NSW CRA/RFA
Steering Committee, 24 Nov 1997. Prepared by the State Forests
of NSW.
- The Eden Burning Study Area Vegetation data
The objective was to examine the effects of integrated harvesting
and fuel reduction burning regimes on dry sclerophyll forests.
The objectives are
- to describe pretreatment patterns of
floristic variation in relation to broad habitat
parameters
- to investigate impact of treatments on
understorey floristic patterns
- to investigate response of individual
species to treatments e.g. changes in abundance,
response mechanisms, patterns of recovery and reproduction.
Details are provided of data collection for understorey
species.
- Yallumba Catchments Vegetation Project
The objective was to examine the effects of integrated harvesting
and unplanned fire on floristic composition.
2. http://www.affa.gov.au/content/
publications.cfm?Category=Forestry
'Vegetation classification and mapping systems for Australian
Forest Management' in National Forest Inventory Australia
(copy of publication is in the main collection of theCharles Darwin University
library).
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5.1
Refer to Case Study 2 (see 'assignments' section) and
your previous ejournal entries of vegetation/flora measurement.
Is there anything you want to add to these notes in this topic?
Do you have any preliminary thoughts on methodologies you
might use in Case Study 2?
This will form the basis of your next online tutorial.
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back to vegetation descriptions
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