Effects of Taiwan Vole (Microtus kikuchii) Herbivory on Yushan cane (Yushania niitakayamensis) Growth in Hehuan Alpine Meadows

Although herbivores are often considered having negatively influence on the recruitment, growth, and survival rate of plants, they could benefit plants as well. The herbivorous consumption of different plant parts could have differential effect on fitness of the consumed plants. Yushan canes (Yushania niitakayamensis) is the dominant plant species, and Taiwan vole (Microtus kikuchii) is the dominant small mammal in alpine meadows at the Hehuan Mt.. The former species is the primary and preferred food of the latter species. In this thesis, investigation was set up to elucidate the relationship between the two species. Hypothesis of the study are (1) Taiwan voles have feeding preference on different parts of Yushan canes; (2) feeding preference can be explained by nutrient contents of different parts: highly preferred parts have higher protein and lower fiber contents than less preferred parts; (3) consumption by Taiwan voles has positive effects on the growth of Yushan canes by increasing light penetration into the canopy and aboveground litter. Feeding preference experiments and nutrient content analyses were performed in the laboratory, and field exclosures and field manipulation of canopy and litter were used to test the hypotheses. The results indicated that the ranks of feeding preference by Taiwan voles were shoot > leaf > culm = rhizome in May, and leaf > shoot = culm = rhizome in January and October. The preference was explained by nutrient contents, particularly the amounts of acid detergent fiber (ADF), crude protein (CP), and ash of Yushan cane parts. The exclusion of voles led to decreased shoot-culm ratios. Both the reduction of canopy cover and litter removal had significant effects on the emergence of new shoots after 1 year of field manipulation, indicating that Taiwan voles could facilitate shoot emergence of Yushan canes through increasing light availability and ground litter. I conclude that although Taiwan voles consume Yushan canes, they could benefit Yushan canes as well.