Si's research focused on paleobotany,[1][3] and he made significant contributions to the classification and evolution of paleobotany, comparative stratigraphic divisions, and phytogeographic distribution. He edited the Paleogene Flora of China, the first work to systematically summarize the problems of Chinese Paleogene flora and terrestrial stratigraphy. His book "Mesozoic Extended Stratigraphic Flora of Northern Shaanxi" was the first to point out the succession pattern of the Chinese Mesozoic flora and to propose a scheme for the delineation of the Chinese Mesozoic terrestrial stratigraphy.[3]
Si also made a significant impact on the field of geology and paleobotany education. He taught the first paleobotany course in China at Tsinghua University and Peking University, and later taught at Nanjing University. He was known for being dedicated to teaching and sharing his insights with students and colleagues. Due to Si's tireless efforts, the study of paleobotany and terrestrial stratigraphy in China was greatly advanced.[3]
