How do Water Regime and Grazing Alter the Reproductive Capacity of Aquatic Plants?
Dr Margaret A. Brock
Botany, Rural Science and Natural Resources,
University of New England
Environment Australia, 2000
Attachment B
Benefits and limitations of three experimental methods for wetland research: reliability to reality from glasshouse, outdoor tank and field scale experimental wetlands
Laurie O'Donnell and Margaret Brock
This project combines the strengths of various scales of experimentation to achieve answers that are applicable at the field scale. Reliability of results was highest in the finer scaled experimental testing under glasshouse conditions, and outdoor experimental tank testing of water regime and grazing interactions (see Casanova and Brock 2000, Attachment a) . Whereas field scale experiments in the University of New England Experimental Wetlands and field observations added greater reality to interpretations.
The approaches used in the development of the project involved the construction of manipulable, experimental wetlands in the field, experimental outdoor tanks and experimental shallow tanks in a glasshouse. Each was designed to be highly appropriate for a particular type of research. Benefits and limitations of each are outlined below.
1. Newholme Experimental Wetlands.
This facility is composed of sixteen earthen ponds located on the University of New England's Newholme Field Laboratory. Water from the adjacent creek can be admitted to or removed from the ponds as required (see Attachments c and d from this report).The features of the Newholme Experimental Wetlands are:
Beneficial Features:
- 16 ponds allowing for possible replication and treatment combinations
- continuously adjustable water level permits unlimited combinations of depth and timing regimes
- passive water level control mechanism negates natural flooding and accommodates evaporation/seepage with little intervention
- appropriate environment for natural seed bank development
- suitable for transplantation of seed bank material by a variety of methods; e.g. cores, bulk or sods
- low disturbance, personnel entry and exit duckboard
- sloped batters simulate natural wetland zones or dam embankments
- whole facility is accessible for sampling
- set in locally typical microclimate and soil type
- water supplied from natural source (Duval Creek)
- relatively expensive, but durable, serviceable, effective and simple
Limiting Features:
- Sixteen ponds limits treatment and replication combinations
- Maximum water depth limited by pond depth (max 0.9m)
- Replacing entire sediment for further research may be impracticable
- Immovable
- Regular system checks and adjustments may be necessary dependent on a particular program of research
- Ponds can lose shape over time due to soil slumping
- Maintenance can be partitioned into a) Short term; easy, accessible, cheap etc. and b) Long term; difficult inaccessible, added expense etc.
Types of data which can be collected using the Newholme Experimental Wetlands:
- seed germination
- plant establishment
- plant establishment propagule type
- amphibious plant type
- plant reproduction
- plant abundance
- plant functional group
- photo scoring of plants in situ
- seed bank sample data
- plant presence and absence
- aquatic animal data
- water physiochemical data
The experimental wetlands have been effective as they have enabled the above range of data to be collected from an experimental simulation at a field scale. The Experimental Wetlands are an appropriate 'tool' and have been used effectively in the implementation of the project:
2. Tank Trial apparatus
This apparatus consists of above ground fiberglass tanks located at the University of New England (UNE) campus. An apparatus suspends the experimental units (plastic plant pots containing wetland material) in the desired depth of water (see Casanova and Brock 2000, appendix a, for details).
Beneficial Features:
- up to 17 water regimes possible in one tank
- replication by number of tanks (up to 12)
- effective water depth adjustable stepwise
- easy access to experimental units
- apparatus allows replication and treatment combinations
- semi-natural microclimatic conditions prevail
- small amounts of plant substrate or seed bank necessary
- simple, effective, inexpensive and durable
Limiting Features:
- water level not continuously variable
- not entirely natural microclimate
- limited subaerial environment
- unnatural (local town) water supply
The types of data that can be collected using the Tank Trial apparatus are:
- mode of reproduction
- flooding depth
- clipped or unclipped plants
This apparatus has proven itself useful for focussing on an aspect of the research , avoiding uncontrollable factors but under largely natural conditions.
3. Glasshouse trial apparatus
This apparatus consists of shallow tanks located on benches in a glasshouse at the UNE campus. The water depth and timing is manipulable, and seed bank cores from wetlands placed in these tanks can be observed closely.
Beneficial Features:
- water depth continuously adjustable up to 200 mm
- 'indoor' environment amenable to data collection regardless of prevailing weather
- low cost tanks
- durable, serviceable and simple
- very accessible experimental units
- disposable food containers, used to collect and germinate seed bank cores
Limiting Features:
- relatively small amounts of seed bank acceptable
- shallow limited maximum water depth
- unnatural growing environment
The types of data collected include:
- plant establishment
- amphibious plant type
- plant reproduction: sexual and vegetative
- species richness
- plant functional group
- photo scoring of plants in situ
- seed bank sample data
- plant presence and absence
This very inexpensive and simple apparatus can reveal a wealth of plant related data and is thus excellent for serious research and also extension and community based projects
Key
Links to another web site
Opens a pop-up window