Chen Zhehan

                                                                                                  School of Life Sciences

Abstract: Since the Industrial Revolution, climate warming, one of the major global climate changes caused by human activities has resulted in many effects on the structure and functioning of terrestrial ecosystems. Simulated warming is the main experimental method to study the response of ecosystems to climate warming. In the past, simulated warming experiments were mainly carried out in grassland ecosystem, while such experiments in forests are still rare. As a main type of terrestrial ecosystem, forests contain high plant diversity where understory herbaceous species represent merely 80% of vascular plants and play an important role in the circulation of materials and energy flow of forest ecosystems. Meanwhile, due to limited dispersal ability, herbaceous plants in forests may respond more obvious to climate warming. Therefore, it is of greater ecological significance to study the response of herbaceous plants in forests to warming. Based on the infrared heating experimental platform in Qingyuan Forest CERN, Chinese Academy of Sciences, this study analyzed the effects of simulated warming (increasing temperature by 2℃ in 0-10cm soil) on the diversity (richness, abundance, diversity index), community structure and composition (coverage, importance value) and functional traits (leaf area, leaf length, mean leaf width, maximum leaf width, ratio of leaf length to width, chlorophyll content, flavonoid content, nitrogen balance index, anthocyanin content) of herbaceous plants in spring, summer and autumn. The main results were as follows: （ 1 ） The warming effect on the surface soil (0-10cm) was stable and the temperature increased by about 2℃, while the soil moisture had no significant change. Air temperature decreased with the increased distance from the ground, and the air temperature rise was less than 2℃. Air humidity decreased with the increased distance from the ground with greater change range than soil moisture. （2）Warming had no significant effect on the richness, abundance and coverage of the herb community in spring, summer and autumn, but the diversity index showed a declining trend. The response of community structure and composition to warming was obvious, mainly manifested as the important value of dominant species increased, but varied among dominant species. Specifically, Brachybotrys paridiformis showed significantly positive response and became the most dominant species in the community, while Cardamine leucantha and Meehania henryi showed negative response, and Hylomecon japonicahas showed no obvious response. The dominant species in spring, Allium monanthum showed obvious negative response, but Adoxa moschatellina showed obvious positive response. The dominant species in summer, Laportea bulbifera had no obvious response. （3）The effects of warming on the 9 functional traits of dominant species were different. For example, anthocyanin content increased significantly, and its range and coefficient of variation (CV) decreased significantly under the warming treatment. The response of leaf length to warming kept consistent among species with a small but significant increase. At the species level, the functional traits of B. paridiformis to warming were the most obvious and the values of 8 functional traits increased; indicating that warming had a positive effect on its functional traits. The defense traits of C. leucantha, H. japonicahas and M.henryi to warming changed greater than the growth traits. After warming, there was no significant change in the relationship between growth traits, and the positive correlation between defense traits increased. However, the correlation between growth traits and defense traits of these four species showed inconsistent response to warming. Among them, the negative correlation of B. paridiformis increased significantly, while that of C. leucantha, H. japonicahas and M. henryi showed no significant change. The trade-off relationship between growth and defense traits of B. paridiformis had no obvious change to warming, and the score coefficient of individual trait characterization did not change significantly to warming, indicating that the functional traits of B. paridiformis had high internal stability. The trade-off relationship between growth and defense traits of C. leucantha, H. japonicahas and M. henryi changed significantly to warming, which forced them to reduce investment in one of their growth or defense capabilities and then invest it in another to cope with the environmental changes. The above results showed that the effects of warming on herbaceous plant communities were mainly manifested as obvious effects on dominant species, and the changes in competitive relations among dominant species caused by warming had different impacts on functional traits, which further received feedbacks at the species and community level. This study can provide a basis for future assessment of how the dominant species would affect the diversity, community structure and composition of herbaceous plants under climate warming, and provide a new perspective for the response of plant functional traits to climate warming.

Read the full article here:       【气候变化】增温对东北温带次生林草本群落结构和功能性状的影响.pdf