The University of Chinese Academy of Sciences (UCAS) announced the winners of the Excellent Doctoral Dissertation 2016 and Excellent Tutor 2016 on September 22. The thesis written by Chen Yajun, a Ph.D graduate of Xishuangbanna Tropical Botanical Garden (XTBG), was awarded the CAS Excellent Doctoral Dissertation Award 2016 and Prof. Cao Kunfang, Chen Yajun’s supervisor, won the title of CAS Excellent Graduate Tutor 2016.
Chen Yajun’s doctoral dissertation was entitled “The water-use characteristics of tropical lianas and the comparison with co-occurring trees”. Lianas have been assumed to have dry season growth advantage compared to their co-occurring trees. However, this assumption seems paradoxical because lianas commonly have wide and long vessels thus may be susceptible to water deficit. To date, the underlying mechanisms responsible for how lianas cope with drought are still unknown. In the study, Chen Yajun and his colleagues selected three tropical forests differing in soil water availability in Xishuangbanna, Southwest China: a tropical karst forest (KF, severe water deficit in the dry season), a tropical seasonal forest (TSF, moderate water deficit) and a flood plain forest (FPF, ever-wet). They determined the anatomicial traits, biomechanic and hydraulic properties for about 74 liana (30 species) and tree species (44 species). They also monitored the sap flow, leaf water status (predawn and midday leaf water potential, Ψpredawn and Ψmidday), gas exchange (photosynthesis and stomatal conductance, Pmax and gs) for 99 liana and co-occurring tree individuals (15 liana and 34 co-occurring tree species) in those three forests over three years. Using stable isotope analysis, they studied the soil water partitioning both in wet and dry seasons and the contribution of leaf water uptake from fog. Besides, they explored how stomatal regulation mediated the diurnal water deficit in diurnal cycle. Finally, they estimated the contribution of stem water storage to daily water use as well as the seasonal changes for lianas.
During his graduate studies under the guidance of Prof. Cao Kunfang, Dr. Chen Yajun has published his research in such journals as New Phytologist, Functional Ecology, Tree Physiology, and American Journal of Botany.
The award of CAS Excellent Doctoral Dissertation firstly started in 2004. Its rigorous selection procedures require that the paper’s research achievement is in high level in innovation and other qualities, which is an important indicator to measure the cultivation abilities of the graduate cultivation units of CAS.
Up to now, four XTBG graduates received the award; they are Tan Zhenghong (2012), Hu Yanru (2014), Jiang Yanjuan (2015), and Chen Yajun (2016).