Forest ecosystems in Great Smoky Mountains National Park (GRSM) have long been affected by natural and human disturbances. Insect outbreaks and fires are the major disturbances affecting forest ecosystems in GRSM with interactions between each other. This manuscript-style thesis research explores these types of forest disturbances occurred in GRSM with two case studies. The first manuscript explores the spatial and temporal patterns of eastern hemlock (Tsuga canadensis L.) defoliation caused by hemlock woolly adelgid (HWA, Adelges tsugae) infestation in GRSM. Hemlock trees play an ecologically vital role in the eastern United States including GRSM. However, they have been facing a rapid infestation by the non-native HWA discovered in the park circa 2002. Moreover, the severe and persistent Chimney Tops 2 Fire occurred in November 2016 also put forest ecosystems in GRSM under threats. The second manuscript examines the spatial variations and driving factors affecting burn severity of the 2016 Chimney Tops 2 Fire in GRSM. The methodology and results from this project will support National Park Service forest management and insect control policies for the GRSM.