Dynamics of phreatophyte root growth relative to a seasonally fluctuating water table in a Mediterranean-type environment
- 632 Downloads
While seasonal redistribution of fine root biomass in response to fluctuations in groundwater level is often inferred in phreatophytic plants, few studies have observed the in situ growth dynamics of deep roots relative to those near the surface. We investigated the root growth dynamics of two Banksia species accessing a seasonally dynamic water table and hypothesized that root growth phenology varied with depth, i.e. root growth closest to the water table would be influenced by water table dynamics rather than surface micro-climate. Root in-growth bags were used to observe the dynamics of root growth at different soil depths and above-ground growth was also assessed to identify whole-plant growth phenology. Root growth at shallow depths was found to be in synchrony with above-ground growth phenophases, following increases in ambient temperature and soil water content. In contrast, root growth at depth was either constant or suppressed by saturation. Root growth above the water table and within the capillary fringe occurred in all seasons, corresponding with consistent water availability and aerobic conditions. However, at the water table, a seasonal cycle of root elongation with drawdown in summer followed by trimming in response to water table rise and saturation in winter, was observed. The ability to grow roots year-round at the capillary fringe and redistribute fine root biomass in response to groundwater drawdown is considered critical in allowing phreatophytes, in seasonally water-limited environments, to maintain access to groundwater throughout the year.
KeywordsBanksia Groundwater Phenology In situ root growth dynamics Root in-growth bags
This research was conducted under an Australian Postgraduate Award associated with Australian Research Council Linkage Project LP0669240. The authors also wish to acknowledge the support of the Water Corporation of Western Australia.
- Bell D, Stephens L (1984) Seasonality and phenology of Kwongan species. In: Pate J, Beard J (eds) Kwongan plant life of the sand plain. University of Western Australia Press, Perth, pp 205–226Google Scholar
- Bureau of Meteorology (2010) Climate statistics for Australian locations. Retrieved from http://www.bom.gov.au/climate/averages/tables/cw_009021.shtml in September, 2010
- Dodd J, Heddle EM, Pate JS, Dixon KW (1984) Rooting patterns of sandplain plants and their functional significance. In: Pate J, Beard J (eds) Kwongan plant life of the sand plain. University of Western Australia Press, Nedlands, pp 146–177Google Scholar
- Eamus D, Hatton T, Cook P, Colvin C (2006) Ecohydrology: vegetation function, water and resource management. CSIRO Publishing, CollingwoodGoogle Scholar
- Freeze RA, Cherry JA (1979) Groundwater. Prentice-Hall Inc., New JerseyGoogle Scholar
- Gentilli J (1972) Australian Climate Patterns. Thomas Nelson, MelbourneGoogle Scholar
- Greacen EL (1981) Soil water assessment by the neutron method. CSIRO (Division of Soils), AdelaideGoogle Scholar
- Hendrick RL, Pregitzer KS (1997) The relationship between fine root demography and the soil environment in northern hardwood forests. Ecoscience 4:99–105Google Scholar
- Kozlowski TT (1997) Responses of woody plants to flooding and salinity. Tree Physiology Monograph 1:1–29Google Scholar
- Kramer PJ, Boyer JS (1995) Water relations of plants and soils. Academic Press Inc., San DiegoGoogle Scholar
- Meinzer OE (1923) Outline of groundwater hydrology with definitions. Water-supply paper 494. US Geological SurveyGoogle Scholar