Use this URL to cite or link to this record in EThOS:
Title: Ecohydrological interactions across a semi-arid grassland to shrubland transition
Author: Turnbull, Laura
ISNI:       0000 0001 3537 9549
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2008
Availability of Full Text:
Access from EThOS:
The aim of this study is to further understanding of ecohydrological interactions between ecosystem structure and function over a transition from semi-arid grassland to sluubland. An ecohydrological framework is outlined, which is used to develop specific research objectives to enable changes in ecohydrological interactions over a grassland to sluubland transition to be discerned. A field-based monitoring approach was employed at the Sevilleta National Wildlife Refuge in New Mexico, USA, using a space for time analogue,to determine how landscape structure and function change at stages over a grassland to sluubland transition. Emphasis was placed on investigating ecohydrological interactions that occur during convective rainfall events, and on the statistical and geostatistical characteristics of vegetation, soil-structure and resource characteristics. Changes in the overall percentage cover and spatial distribution of vegetation were observed at stages over the transition, as were changes in surface-soil characteristics, with an increase in soil nutrients and finer soil under vegetation. The ranges at which these surface characteristics show autocorrelation do not generally appear to be related to changes in the range at which vegetation is spatially autocorrelated across the plots. There are overall increases in the loss of water, sediment and nutrients from plots at stages over the transition, although greatest amounts of runoff were monitored in the latter transitionary stage, prior to full domination by sluubs. Nutrient losses were dominated by particulate-bound forms. A series of numerical experiments were carried out using MAHLERAN, Model for Assessing Hillslope to Landscape Erosion, Runoff and Nutrients, to explore further the differences in runoff, erosion and nutrient dynamics over the transition. Results show that the spatial dynamics of runoff change over the transition, with the development of more concentrated flow lines and an increase in the connectivity of runoff-generating areas, which, in addition to the effects of soil-surface characteristics on runoff, erosion and nutrient dynamics, change the scales over which sediment and nutrients are redistributed. However, there are disparities between the simulated spatial patterns of nutrient redistribution and the spatial distribution of soil nutrients measured across the transition. Therefore, results of this study indicate that interactions between ecosystem function and structure are likely to be driven in part by processes operating at spatial and temporal scales other than those related to runoff events, which need to be determined in order to understand fully ecohydrological interactions operating o,:'er a transition from grassland to sluubland. Thus, it is proposed that further research should undertake a spatially-explicit ecohydrological modelling approach, in which the interactions between ecological, hydrological and biogeochemical processes over space and time can be investigated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available