Forest Distribution on Small Isolated Hills and Implications on Woody Plant Distribution under Threats of Global Warming

• Main Authors: Chi-Cheng Liao, Shih-Chieh Kuo, Chi-Ru Chang
• Format: Article
• Language: English
• Published: National Taiwan University 2012-09-01
• Series: Taiwania
• Subjects: Altitudinal gradient; forest line; global warming; species richness; Yangmingshan National Park
• Online Access: http://tai2.ntu.edu.tw/taiwania/abstract.php?type=abstract&id=1181

Treelines have been found to be lower in small isolated hilltops, but the specific dynamics behind this unique phenomenon are unknown. This study investigates the distribution patterns of woody plants in Yangmingshan National Park (YMSNP), Northern Taiwan in search of the limitation mechanisms unique to small isolated hills, and to evaluate potential threats under global warming. Forests distributed between 200 to 900 m above sea level (ASL). Remnant forest fragments between 400 and 900 m ASL, have the highest species richness, and should be protected to ensure future forest recovery from the former extensive artificial disturbance. The lower boundary is threatened by urban and agricultural development. The lack of native woody species in these low elevation zones may cause a gap susceptible to invasive species. A consistent forest line at 100 m below mountain tops regardless of elevation suggests a topography-induced instead of an elevation-related limiting mechanism. Therefore, upward-shift of forests, caused by global warming, might be limited at 100 m below hilltops in small isolated hills because of topography-related factors. The spatial range of woody plants along the altitudinal gradient, thus, is likely to become narrower under the combined pressures of global warming, limited elevation, exposure-related stress, and artificial disturbance. Management priorities for forest recovery are suggested to include preservation of remnant forest fragments, increasing forest connectivity, and increasing seedling establishment in the grasslands.