TheImprovement ofTropical and Subtropical Rangelands

202 IMPROVEMJ:NT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
Practical procedures for cleaning and handling UlNre high seed quality.
Further information regarding the availability of germ plasm
appropriate for range improvement projects in the tropics and subtropics
could be obtained from the following sources:
Division of Tropical Crops and Pastures
Commonwealth Scientific and Industrial Research Organization
Private Mail Bag, MSO
Townsville, Queensland 4810
Australia
Forest Resources Development Branch
Forestry Department
Food and Agriculture Organization of the United Nations
Via delle Terme di Caracalla
00100 Rome
Italy
International Council for Research in Agroforestry
P.O. Box 30677
Nairobi
Kenya
MAINTENANCE 0' BIOLOGICAL DIVERSITY
Questions ofreduced biological diversity have been raised in relation
to range improvement projects carried out in the western United
States during the 19408 and 19508. Many of the early projects were
designed for sites where the perennial bunch grat!llleS were severely
reduced by overgrazing, and where other shrubs of low palatability
to livestock had come to dominate the sites. Remedial measures to
remove or reduce the dominant shrubs, such as the application of
broad-spectrum chemical herbicides or mechanical removal, also had
an adverse impact on other species susceptible to the drastic control
methods. The result was a severe reduction in the species diversity
of the range vegetation.
In addition to the 1088 ofdiversity caused by the control measures,
the number of species included in the seeding mix were very limited,
sometimes consisting only of wheatgrat!llleS. Experience in securing
a satisfactory degree of establishment and in managing grazing on