In this study, a new approach is presented that combines forest phenology and Landsat vegetation indices to estimate evergreen understory bamboo coverage in a mixed temperate forest. It was found that vegetation indices, especially the normalized difference vegetation index (NDVI) derived from leaf-off (winter)
IntroductionUnderstory plants are important elements of forest structure and composition, providing habitat and forage for wildlife, and contributing to flora diversity (McKenzie and Halpern, 1999;Rettie et al., 1997). Bamboos are typical understory tree-grasses in Japanese, Chilean, and Chinese temperate and subalpine forests where they achieve a high degree of dominance (Franklin et al., 1979;Taylor and Qin, 1988;Veblen, 1982). Many mammals and birds rely on this special niche as sites for foraging and nesting, in which the most famous are giant panda (Ailuropoda melanoleuca), red panda (Ailurus fulgens), and golden pheasant (Chrysolophus pictu) (Gong et al., 2006;Reid et al., 1991;Reid et al., 2004;Schaller et al., 1985). Knowledge of understory bamboo presence/absence and its abundance would enable wildlife managers to identify areas of suitable habitat for dependent animals and birds
Understory Bamboo DiscriminationUsing a Winter Image Tiejun Wang, Andrew K. Skidmore, Albertus G. Toxopeus, and Xuehua Liu (Borkowski and Furubayashi, 1998;Diaz et al., 2005;Liu et al., 2005;Reid et al., 2004;Warner, 2002). However, our understanding of understory bamboo spatial distribution at local and national levels is limited, as previous studies focused on ground surveys executed over small and intensively study sites. In addition, the complexity of bamboo distribution, influenced by human activities (clear cutting and fire), as well as periodical mass flowering and die-off (Reid et al., 1989), makes the up-scaling to large areas through conventional point-based environmental modeling extremely difficult. A few studies have been conducted at large landscape level. For example, the panda habitat assessment in the Wolong Nature Reserve of Sichuan (Liu et al., 2001) and the Qinling Mountains of Shaanxi (Loucks et al., 2003) in China assumed that the distribution of understory bamboo has a constant spatial cover. In these studies the authors noted that the unsuitable habitat would be underestimated, because critical information affecting panda habitat, such as bamboo distribution, was not available for the entire region. Remote sensing may be suitable for mapping forest understory across large areas. For example, Morain (1986) conducted a primary investigation on understory bamboo assessment in a Chinese panda reserve using 35 mm color infrared air photographs (scale 1:12 000) acquired in April (leaf-off season). He reported that three types of understory bamboo status (mixed with deciduous trees, mixed with coniferous trees, and mainly deciduous vegetation without bamboo) may be visually distinguished. By utilizing summer TM image and an unsupervised classification approach, Stenback and Congalton (1990) de...