Modeling Potential Range Expansion of the Invasive Shrub Leucaena leucocephala in the Hengchun Peninsula, Taiwan

• Published in: Invasive plant science and management 2013-10, Vol.6 (4), p.492-501
• Main Authors: Chiou, Chyi-Rong, Wang, Hsiao-Hsuan, Chen, Yen-Jui, Grant, William E, Lu, Ming-Lun
• Format: Article
• Language: English
• Subjects: agricultural land; altitude; Anthropogenic factors; Biodiversity; biogeography; Biological invasion; boosted regression trees; Climatic conditions; climatic factors; control methods; cost effectiveness; data collection; ecological invasion; edge effects; environmental health; Expansion; Flowers & plants; Forest management; Forests; Generalized linear models; habitats; Invasive plants; Invasive species; landscapes; Leucaena leucocephala; managers; monitoring; Native species; Nonnative species; planning; prediction; risk; rivers; roads; secondary forests; species distribution models; surface water; surveys; temperature; Trees
• ISSN: 1939-7291; 1939-747X; 1939-747X
• DOI: 10.1614/IPSM-D-13-00010.1

Prediction of invasive species distributions from survey data is widely recognized as a significant component of forest management and conservation planning. Leucaena leucocephala is the most aggressive invasive shrub and tree in the Hengchun peninsula in southern Taiwan. We analyzed geo-referenced data to identify potential variables of invasion and to predict likelihood of further invasion using boosted regression trees. Our results, which classified 92% of the cells correctly with regard to species presence and absence, indicated probability of invasion is correlated with climatic conditions (temperature and precipitation), landscape features (altitude; slope ratio and aspect; percentages of natural or secondary forest, agriculture land, developed area, and water bodies; and distances to the nearest forest edge and river), and anthropogenic factors (length of forest edge, and distances to the nearest road and agriculture land). The most influential variables are average annual temperature, altitude, precipitation, and slope. Continued range expansion by L. leucocephala is most likely to proceed (1) from the eastern and western portions toward the central portion of Hengchun township and (2) throughout the southern and toward the eastern portions of Manjhou township. Our model should provide useful information to aid forest managers in the development of long term monitoring and control strategies for L. leucocephala, in the early detection and eradication of newly established invasions, and also a framework for the integration and analysis of new presence and absence field data as they become available. Nomenclature: White leadtree, white popinac, and jumbay, Leucaena leucocephala (Lam.) de Wit. Management Implications: Leucaena leucocephala continues to expand its ranges in the southern Taiwan, and reliable prediction of habitats at risk is needed urgently. We drew upon extensive geo-referenced datasets to develop an invasion distribution model predicting possible range expansion of L. leucocephala in the Hengchun peninsula, Taiwan. Our analyses suggest that continued range expansion of L. leucocephala. However, the opportunity exists for reducing the likelihood of invasions via increased monitoring and early control efforts focused on low-elevation lands with low slope ratios that are close to roads, water, and/or forest edges. Areas surrounding agricultural and developed areas also should be targeted for prompt inspection and potential control measur