Invasion potential of Sapium sebiferum in the Central Valley of California (US)
Sapium sebiferum (= Triadica sebifera, Euphorbiaceae) is an ornamental tree native to eastern Asia. This species is known to be invasive in the Gulf Coast region of the USA, where it occupies wetlands, prairies, woodlands and forests. In this region, it is reported to displace native plants and to dominate communities often by forming monospecific stands. In invaded areas, insectivorous birds find the quality of woodlands diminished because of low insect populations. Although S. sebiferum was introduced to the Southern USA in the late 18th century, it was only later, after extensive planting that colonization of natural areas was reported. S. sebiferum is also reported as present, but not yet as invasive in Algeria, France, India, Martinique, South Africa, Sri Lanka and Sudan. Recent climate matching modelling with CLIMEX showed no invasion potential of S. sebiferum in California when coarse scale climatic averages were used. This was largely attributed to the Californian long and dry summers, which are suspected to filter out many exotic plants. However, when summer precipitation was increased in the model to simulate locally elevated soil moisture, much of Californian riparian habitats (especially in the Central Valley) emerged with climate appropriate for S. sebiferum.
S. sebiferum is tolerant to a wide range of abiotic and biotic conditions. Its seeds are dispersed by both birds and water. The reproductive success of the species was measured in California and revealed that the mean seed production of mature trees was 39 ± 9 seeds per tree. Seed viability was evaluated at 95%. Numerous recently naturalized populations demonstrate that riparian areas in the Central Valley of California are susceptible to invasion by S. sebiferum. In California, it is therefore recommended that land managers should monitor more particularly the edges of rivers and streams where currents are more likely to deposit seeds and where the environmental conditions are favourable to germination and seedling survival of S. sebiferum.
Bower MJ, Aslan CE, Rejmánek M (2009) Invasion potential of Chinese Tallowtree (Triadica sebifera) in California’s Central Valley. Invasive Plant Science and Management 2, 386-395.
Global Invasive Species database (2010) Triadica sebifera. http://www.issg.org/database/species/ecology.asp?si=712;fr=1;sts=;lang=EN