| Abstrakt: |
Context: It is important to understand the way in which wild herbivore grazing affects decadal vegetation dynamics after cessation of unnatural disturbances, especially in a context of climate change. Aims: We investigated the decadal effects of different grazing regimes on treeless subalpine vegetation recovery from stock grazing and burning, on sites of different environmental character and initial state. Methods: At each of four sites, two fenced areas that excluded mammalian herbivores, two that allowed in only rabbits and two grazed control plots were monitored every 5 years between 1991 and 2021. General linear models were developed to explain variation in change over the 30 years in different cover types. The years in which peak and trough values occurred were also determined, as were the incidence and direction of differences between treatments in sites and years. Key results: There was marked variation in change over 30 years between the sites and lifeforms. Exclusion of mammalian herbivores increased the slow rate of revegetation. There was little effect from rabbits by themselves. Unexpectedly, the cover of both short and tall herbs was not promoted by grazing exclusion. Short term climatic variation affected some cover types, with many peaks and troughs in the dry year of 2001, but it was not possible to disentangle decades scale climate change effects from the process of recovery after disturbance. Conclusions: The slight increase in revegetation rates in the absence of native herbivores and rabbits does not justify culling. Restoration interventions appear to be unnecessary. The prospect of increasing fire incidence and deer numbers suggests that it is desirable to continue monitoring the plots. Long-term monitoring on Tasmania's Eastern Central Plateau provides an opportunity to document the process of recovery from fire and stock grazing and the impacts of wild herbivores. After 30 years, vegetated ground cover has increased both inside and outside grazing exclosures. Although results between the four sites were variable, natural regeneration will occur without management intervention and in the absence of a catastrophic disturbance such as wildfire. Photographs by Kerry Bridle. [ABSTRACT FROM AUTHOR] |
