The effect camels have on the ability of parkinsonia (Parkinsonia aculeata L.) to set seed

摘要

In recent years a concerted effort has been made by research organisations to better understand the biology and ecology of the invasive shrub parkinsonia (Parkinsonia aculeata L.) and to develop integrated control strategies. Some land managers have also been testing innovative methods. One such example is the use of camels, with a small but increasing number of landholders purchasing them for the purpose of woody weed control in northern Australia. On two properties in the Charters Towers region, atrial was established to quantify whether camels have a detrimental affect on parkinsonia or are potential dispers-ers. In browsed and unbrowsed paddocks, the level of pod production, size of seedbanks and presence of seed in camel dung were directly compared. Under heavy continuous browsing, pod production per tree averaged less than one in browsed paddocks in comparison to 3801 per tree under unbrowsed conditions. The soil seedbank present under the canopy of trees was similarly reduced, dropping from207 seeds per square meter in unbrowsed paddocks to one seed per square meter in browsed areas. In terms of dispersal, camels appear to be low risk, with most dung samples containing less than two seeds. These results suggest that the preferential browsing nature of camels could compliment traditional control methods and lead to a reduced seedling recruitment from the depleted soil seedbank. However, further research is warranted to clarify camel diet preferences particularly with regards their potential impact on native shrubs.