PARENT SESSION
Poster Session #64: Long Term Ecological Research.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Recovery of savanna vegetation in northern Australia: 1973-2000.

LUDWIG, JOHN^*,1, BASTIN, GARY¹, EAGER, ROBERT¹, LIEDLOFF, ADAM¹, ANDISON, REGINALD², COBIAC, MICHAEL³, ¹ CSIRO Sustainable Ecosystems, Atherton, Queensland, Australia² Queensland Primary Industries, Bowen, Queensland, Australia³ Northern Territory Primary Industries and Fisheries, Katherine, Northern Territory, Australia

ABSTRACT- Open-range cattle have grazed the tropical savannas of northern Australia since the late 1800s. Some areas were heavily utilized by these cattle, and by feral horses and donkeys, and by the early 1970s were nearly devoid of vegetation, for example, areas near permanent water-holes along Kidman Creek in the Northern Territory. In July 1973, exclosures were erected on three areas near Kidman Creek, two on calcareous red loam soils, and one on cracking gray clays. The recovery of vegetation within and outside these exclosures was measured annually between 1974 and 1979, and then again in 1989, 1994 and 1999. Data from permanent transects and photo-points illustrate that from a degraded state in 1973 recovery of total plant biomass on red loams was relatively rapid, but changes in plant composition were still occurring after 27 years; perennial tussock grasses were replacing annuals and short-lived perennials. Vegetation outside exclosures also improved because of better cattle management over the past 30 years. On gray clays, ribbon grass and flinders grass have dominated since 1973, with composition and yields appearing to vary little over the past 27 years. The density of native tree species, particularly rosewood, increased in general, but more so within exclosures. These findings have implications for the management of savannas, with the control of grazing and woody vegetation being important considerations.

KEY WORDS: savannas, vegetation change, semiarid, rangelands