
TY  - JOUR
A1  - Anderson, Val Jo 
A1  - Hodgkinson, Ken C. 
T1  - Grass-mediated Capture of Resource Flows and the Maintenance of Banded Mulga in a Semi-arid Woodland
JF  - Australian Journal of Botany
JO  - Aust. J. Bot.
Y1  - 1997
VL  - 45
IS  - 2
SP  - 331
EP  - 342
KW  - 
UR  - https://doi.org/10.1071/BT96019 
N2  - It has been proposed for semi-arid and arid regions that the scarce resources of water and nutrients normally limiting plant growth are distributed patchily in the landscape in order to maintain both stability and productivity (Tongway 1990). &#8216;Fertile patches&#8217; are maintained by the concentration of resources during flows and when resource control is weakened their persistence is threatened. This proposition was tested by comparing water relations of perennial life-forms in the nutrient and water rich &#8216;island-bands&#8217; of mulga (Acacia aneura F.Muell. ex Benth.) shrubs, with and without perennial grasses. Dawn xylem water potential (dawn &psi;x) and stable hydrogen isotope composition data showed that A. aneura and companion grasses competed for soil water, whereas the poplar box (Eucalyptus populnea F.Muell.) trees accessed additional sub-soil water. During a drying cycle, dawn &psi;x of A. aneura on the upslope portion of &#8216;island-bands&#8217; was &#8211;2 MPa where grass was abundant, and &#8211;4.8 MPa where grasses were killed by heavy grazing. On the downslope portions, dawn &psi;x of A. aneura was similar at &#8211;4.2 MPa. Recruitment of A. aneura was occurring in the upslope portion, but was less where there were no grasses. There were more dead A. aneura shrubs on the downslope portion and in grass-free &#8216;island-bands&#8217;. The results suggest that removal of perennial grasses by grazing shortens the period of water supply to A. aneura shrubs in &#8216;island-bands&#8217; and they prematurely die during low rainfall periods. Furthermore, continued grazing pressure from domestic and non-domestic herbivores will prevent restoration of landscape processes necessary for the survival of these shrubs and associated flora. 
ER  -

