We have focused on studying the interactions between plants and their environment. The objectives are to understand (1) the factors responsible for the distribution pattern of plants in Taiwan, and (2) the underlying acclimation and adaptation process that increase the fitness of individual phenotypes under different environment. In addition, we have applied stable isotope techniques to study functions, energy flow and nutrients cycling, of ecosystems.

Following subjects have been studied in the past five years.

1. Ecophysiological study of mangrove species in Taiwan. We have investigated the adaptation mechanisms of Kandelia candel to salinity and factors affecting the distribution pattern of mangrove species in Taiwan. We found that sensitivity to low winter temperatures is a primary limiting factor in the distribution of the mangrove species Avicennia marina along the western coast of Taiwan.

2. Ecophysiological study of wild soybeans in Taiwan. The wild soybeans in Taiwan have differentiated in their photosynthetic susceptibility to water availability and salinity. Different mechanisms are attributed to the inhibition effect of salinity on photosynthesis of the three species.

3. Photosynthetic characteristics of endemic plant species. 13C ratio of endemic plant species are currently analyzed to identify photosynthetic pathways and to compare their long-term photosynthetic water use efficiency. The long-term goal of this study is to understand the photosynthetic characteristics of these endemic plants, especially those distributing at high elevations.

4. Carbon flux and nutrient dynamics in Yuanyang Lake Nature Preserve. Currently, we focus on investigating N acquisition mechanisms adapted by dominant plants species in this naturally acidified, nutrients limited forest.

5. Stable Isotopes Analyses and Trophic Linkages. Stable isotope ratios of carbon and nitrogen of biologically important components were analyzed to identify carbon sources that support the aquatic systems and to defining trophic positions of major components in different habitats of Lanyang River.

W.Y. Kao. 2010. d13C and N contents of two aquatic plants,Spaganium fallax and Schenoplectus mucronatus, in a subtropic mountainous lake. Taiwania 55:54-59.

W.Y. Kao and B. L. Lin. 2010. Phototropic leaf movements and photosynthetic performance in an amphibious fern, Marsilea quadrifolia. Journal of Plant Research 123:645-653.

W.Y. Kao. 2011. Na, K and Ca contents in roots and leaves of threeGlycine species differing in response to NaCl treatments. Taiwania 56: 17-22.

Wu, T.-C. and W.-Y. Kao. 2011. Ecophysiological traits of leaves of three Marsilea species distributed in different geographical regions. Taiwania 56:279-286.

Chang, H.Y., S-H. Wu, K.-T. Shao, W.-Y. Kao, C.-J. Maa, R.-Q. Jan, L-L. Liu, C.-S. Tzeng, J-S. Hwang, H.-L. Hsieh, S.-J. Kao, Y.-K Chen and H.-J. Lin. 2012. Longitudinal variation in food sources and their use by aquatic fauna along a subtropical river in Taiwan. Freshwater Biology 57: 1839-1853

Huang, Y. L. S.-J. Chen and W.-Y. Kao. 2012. Floral biology ofBidens pilosa var. radiata, an invasive plant in Taiwan. Botanical Studies 53: 527-533.

Huang, Y. L. and W.-Y. Kao. 2014. Different breeding systems of three varieties of Bidens pilosa in Taiwan. Weed Research 54: 162-168.

Hsu, H.-M. and W.-Y. Kao. 2014. Vegetative and reproductive growth of an invasive weed Bidens pilosa L. var. radiata and its noninvasive congener Bidens bipinnata in Taiwan. Taiwania 59: 119-126.

T.-N. Yang , T.-Q.Lee , M.-Y. Lee , C.-A. Huh , P. A. Meyers , L. Lowemark ,L.-C. Wang ,W.-Y. Kao , K.-Y. Wei , R.-F. Chen, H.-F. Chen , S.-H. Chen, J.-T. Wu, L.-J. Shiau , Y.-G. Chen, Y.-C. Hsieh.  2014. Paleohydrological changes in northeastern Taiwan over the past 2 ky inferred from biological proxies in the sediment record of a floodplain lake. Paleogeography, Paleoclimatology, Paleoecology 410: 401-411.

Tsai, M.-Y., S-H. Chen, and W.-Y. Kao. 2015. Microsporangium development in two species of Oxalis (Oxalidaceae) with different male fertility. Flora 213: 85-92.

Huang, Y. L. and W.-Y. Kao. 2015. Chromosomal number of populations of three varieties of Bidens pilosa in Taiwan. Botanical Studies. DOI 10.1186/s40529-015-0107-5

Ho, C.-Y, M.-Y.Tsai, Y.-L. Huang, and W.-Y. Kao. 2016. Ecophysiological factors contributing to the invasion ofPanicum maximum into native Miscanthus sinensisgrassland in Taiwan. Weed Research 56 (in press)