IX-B2, 2012 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B2, 2012 
XXII ISPRS Congress, 25 August - 01 September 2012, Melbourne, Australia 
35 
numbers. Journal 
morphology and 
Cooper Creek, 
FOREST DISTURBANCE LEADS TO THE RAPID SPREAD OF THE INVASIVE 
LEUCAENA LEUCOCEPHALA IN TAIWAN 
J. C. Chen a , C. T. Chen h *, A. S. Jump c 
upstream drainage 
the United Stated 
Environment and 
'll. Hydrographic 
:ainous Regions. 
cience, 38(2), pp. 
a Assistant Professor, Department of Forestry, National Pingtung University of Science and Technology, Corresponding 
Author, No.l, Shuehfu Rd., Neipu, Pingtung, 91201 Taiwan -john@msa.hinet.net 
b Professor, Department of Forestry, National Pingtung University of Science and Technology, Corresponding Author, 
No.l, Shuehfu Rd., Neipu, Pingtung, 91201 Taiwan - cct@gisfore.npust.edu.tw 
c Senior Lecturer in Plant Ecology, Biological and Environmental Sciences, School of Natural Sciences, University of 
Stirling, Stirling, FK9 4LA, UK - a.s.jump@stir.ac.uk 
KEY WORDS: Exotic plants, Ecological invasion, Leucaena leucocephala 
¡is of watershed 
icon Geophysical 
ABSTRACT: 
ridges of a graph. 
1. 
r meaning. Earth- 
This study, based on different investigative documents and analytical methods, elucidates spatial distribution of habitats for major 
invasive exotic plants, Leucaena leucocephala, in Taiwan. Results show that Leucaena leucocephala is most harmful to broad 
leaved trees and its invasion directly relates to changes in the physical environment. Leucaena leucocephala can bloom and bear 
fruits all year round and during the period of seeds sprouting and saplings, the invasion varies greatly among different soil types. 
Leucaena leucocephala prefers weakly acidic soil, though it grows well with other soil textures and nutrients as well. The average 
spreading rate of Leucaena leucocephala is 3.55 ha year' 1 on abandoned farm land calculated from the aerial photographs taken in 
1982, 1992, 2003, and 2007. 
1. INTRODUCTION 
Failure of human beings to effectively control exotic plants they 
introduce for their own benefit may affect the original 
ecological system in a short period of time, and may even lead 
to reduction in the variety of species. Once exotic plants 
succeed in invading and occupying a certain plot within an 
ecological system, no matter what methods we adapt to prevent 
and control them, much time and effort, even with eradication 
procedures, must be invested. It will cause major impact on the 
ecological system over a period of time; therefore, prevention, 
control, and research on the invasion of exotic plants have been 
given much attention (Moody and Mack, 1998). 
The number of exotic plant species on Taiwan island has 
recently reached 4,516 (Lai, 1995). Most of them were imported 
via human economic activity; yet, the introduced plants were 
planted and bred intentionally, and humans failed to manage 
them properly as they multiply. Therefore, exotics may diffuse 
out to open fields, harm the ecological system and become 
invasive plants. In recent years, the detriment to the ecological 
system by Leucaena leucocephala has already spread over the 
island now 20010, and many plants cannot grow and develop 
effectively in their usual habitats because of this invasion. The 
invasion and diffusion (augmentation) of alien species have 
long been recognized highly complicated processes. The 
uncertainty of these intrusions has resulted both from their 
extremely complicated mechanisms and the lack of information 
on the range and detail of the invasive species. Fundamental 
information derived from long term inspection is necessary for 
understanding and clarifying this uncertainty. The 
comprehensive data will enhance the accuracy of a postulated 
invasive pattern. It has been shown lately that the stronger the 
interference the easier the invasion, especially for artificial 
disturbance caused by humans (Duggin and Gentle, 1998 i 
Petren and Case ,1998). The invasive plants establish their 
domains at forest edges or road corridors when sufficient 
sunlight becomes available due to the formations of artificially 
developed segments, abandoned farm and fragmented terrain 
due to the construction of roads and buildings (Song et ah, 2005; 
Hawbaker and Radeloff, 2004; Chung and Lu, 2006). 
In this research we used different methods to investigate the 
Leucaena leucocephala, which seriously affect ecological 
environments in Taiwan. After analysis of the harmful effect on 
habitat, we review its special distribution and environmental 
impacts by means of global positioning system (GPS), 
geographical information system (GIS), remotely sensed data, 
and phonological study. The remote sensing technique is one of 
the best and widely method to investigate the damage area of 
exotic plants (Krumpe, 1972 : Lonsdale, 1993; Bulman, 2000; 
David et ah, 2000). 
2. MATERIALS AND METHODS 
2.1 The areas covered in this study 
The climate of Taiwan includes both tropical and subtropical 
region. The southern area, north to Tropic of Cancer, has a 
tropical monsoon climate, and the northern area, south to 
Tropic of Cancer shows a subtropical monsoon. The climate 
over the entire island is characterized by high temperature, high 
humidity, and strong wind. There is a seasonal difference 
among all regions. The annual average temperature is about 20 
°C, while that for average rainfall is about 2,500 mm (highest 
during May to October, more in mountains than in flat land; 
more on the east coast than on the west coast : more in the 
north than in the south ) (King and Su,1993). High 
temperatures and humidity facilitate growth and spread of 
exotic plants. This research was conducted on the Renting