Effects of Plants on Soil-Forming Processes: Case Studies from Arid Environments
- 2.3k Downloads
Bulk deposits of aeolian sand accumulated over recent timescales provide instructive systems for examining effects of colonising vegetation on soil development. The two contrasting case studies presented here are eucalypt woodland in a dune system in southwest Australia and the rubified sand seas of the United Arab Emirates. In the former, clay pavements forming under the lateral root catchments of the eucalypts are shown to be constructed from iron, aluminium and other mineral elements abstracted from ground waters by deep roots. The pavements concerned have a marked restrictive influence on understorey density and biodiversity while also having an overall role in maximising effectiveness of usage of water and nutrients by the trees in question. Timescales and amounts of iron uplifted in this manner are estimated for the system. In the Arabian example, the occurrence of intense reddening (rubification) of sand towards the mountains of Oman is well known, and abiotic processes have been implicated in the phenomenon. In this chapter, we invoke involvement of a biotic component, having demonstrated a relationship between vegetation density and extent of rubification as seen in a positive correlation between increased reddening and cumulative vegetation encountered as one moves from coast to mountains. We hypothesise that uplift of iron by deep-rooted shrubs/trees might be the agent responsible for progressive reddening. Definitive testing of this hypothesis is required, particularly by analysing for iron in xylem sap flowing up through taproots and looking for evidence of its subsequent release into superficial layers of sand surrounding lateral roots of the trees.
KeywordsDesert Hydraulic lift Iron Rubification Sand Trees
We gratefully acknowledge assistance provided by the Environment Agency-Abu Dhabi (EAD) and Dubai-based the International Center for Biosaline Agriculture (ICBA). Iron oxide data was kindly provided by Kevin White of University of Reading. Andrew Buchanan and Phil Goulding helped prepare Figs. 17.1 , 17.2 and 17.4 . The Australian component of this work was carried out with the support of the South Coast Natural Resource Management Incorporated. The drawing in Fig. 17.3a was kindly provided by Noel Schoknecht.
- Anton D, Ince F (1986) A study of sand colour and maturity in Saudi Arabia. Z Geomorphol NF 39:339–356Google Scholar
- Boogert NJ, Paterson DM, Laland KN (2000) The implications of niche construction and ecosystem engineering for conservation biology. BioScience 56:569–577Google Scholar
- Bresler H (1982) The north-eastern Rub al-Khali within the borders of the United Arab Emirates. Z Geomorphol NF 26:495–504Google Scholar
- Dawson TE (1993) Hydraulic lift and water use by plants: implications for water balance, performance and plant-plant interactions. Oecologia 95:565–574Google Scholar
- EAD (2009) Soil survey of Abu Dhabi Emirate. Extensive survey, vol I. Environment Agency Abu Dhabi, Abu Dhabi, p 506Google Scholar
- Emerman SH, Dawson TE (1996) Hydraulic lift and its influence on the water content of the rhizosphere an example from sugar maple, Acer saccharum. Oecologia 108:273–278Google Scholar
- Glennie KW (2001) Evolution of the Emirates’ land surface: an introduction. In: Hellyer P, Al-Abed I (eds) The United Arab Emirates: a new perspective. Trident Press, LondonGoogle Scholar
- Ludwig F, Dawson TE, Kroon H, Berendse F, Prins HHT (2003) Hydraulic lift in Acacia tortilis trees on an East African savanna. Oecologia 134:293–300Google Scholar
- Odling-Smee FJ, Laland KN, Feldman MW (2003) Niche construction: the neglected process in evolution, vol 37, Monographs in population biology. Princeton University Press, PrincetonGoogle Scholar