## 4 Discussion
### Glacial-Interglacial Variability in \(\delta^{13}\)C\({}_{\text{org}}\)
These results indicated that central and eastern China have been equally affected by the cyclic changes during the LG. Notably, during the MIS 4 stage, the values of \(\delta^{13}\)C\({}_{\text{org}}\) composition for the CQS, Luochuan, Lantian and Xunyi loess sections were more negative than those for the MIS 3 stage (Figure 5a-d). The values of \(\delta^{13}\)C\({}_{\text{org}}\) composition for the Yuanbao loess section west of the CLP and the Axike loess section north of the Tianshan Mountains in the L1S1 (MIS 3) stage were more negative than those in the L1L2 (MIS 4) stage (Figure 5e,f). The values of \(\delta^{13}\)C\({}_{\text{org}}\) composition of the CQS, Luochuan, Lantian and Xunyi loess sections were different, however, the \(\delta^{13}\)C\({}_{\text{org}}\) curves in the four loess sections are similar during the LG (Figure 5a-d,g). This indicated that the vegetation succession in the Shengshan Island area, under the impact of climatic change during the LG, was synchronized with the existing records previously reported from central China [40,46]. Generally, the variations of the \(\delta^{13}\)C\({}_{\text{org}}\) records in six loess profiles also reflected the cycle changes of the climate during the LG. At the same time, when discussing the variations of the \(\delta^{13}\)C\({}_{\text{org}}\) composition in different areas during the LG, the differences in regional climate in different regions should be considered, such as elevation, seasonal precipitation and temperature [48, 49]. Climatic change has a significant impact on regional vegetation and the relative biomass of C\({}_{3}\) and C\({}_{4}\) plants. Figure 5: Vertical distribution characteristics of (**a**) \(\delta^{13}\)C\({}_{\text{org}}\) records of CQS section; (**b**) Luochuan loess section [40]; (**c**) Lantian loess section [40]; (**d**) Xunyi loess section [46]; (**e**) Yuanbao loess section [7]; (**f**) Axike loess section [16]; (**g**) Marine oxygen isotope records [47]. Environmental Factors Driving \(\delta^{13}\)C\({}_{\text{org}}\) Changes during the Last Glacial Period  
As is known to all, the most important external factors, such as precipitation, temperature and atmospheric CO\({}_{2}\), affect changes in the \(\delta^{13}\)C\({}_{\text{org}}\) composition of loess [50; 51; 52]. As shown in Figure 6, in order to discuss the environmental mechanism driving the variations of \(\delta^{13}\)C\({}_{\text{org}}\) composition for the CQS loess section from the perspective of external environmental factors, we compared the \(\delta^{13}\)C\({}_{\text{org}}\) records of the CQS section, C\({}_{4}\) abundance in the CQS section, the \(\chi_{\text{fd}}\) in the CQS section, the oxygen isotope record from Chinese stalagmite [53], the East Asian Summer Monsoon record [54], ocean temperature records from Antarctica Dome C ice cores [6; 55], the Greenland Ice-core Project (GRIP) marine oxygen isotope records [56] and the atmospheric CO\({}_{2}\) concentration recorded in the Antarctic ice cores [57]. Figure 6: (**a**) The \(\delta^{13}\)C\({}_{\text{org}}\) record of the CQS section; (**b**) C\({}_{4}\) abundance in the CQS section; (**c**) \(\chi_{\text{fd}}\) of the CQS section; (**d**) oxygen isotope records from Chinese stalagmite [53]; (**e**) the East Asian summer monsoon records [54]; (**f**) ocean temperature records from Antarctica Dome C ice cores [6; 55]; (**g**) GRIP marine oxygen isotope records [56]; (**h**) atmospheric CO\({}_{2}\) concentration recorded by Antarctic ice cores [57]. Precipitation played an important role in the paleovegetation of the East China Sea islands. The \(\chi_{\text{fd}}\) of the CQS loess section was higher in the MIS 3 stage than in the MIS 4 stage (Figure 6c,e), suggesting that precipitation was significantly strengthened in the MIS 3 stage. The high precipitation level inferred from \(\chi_{\text{fd}}\) was positively correlated with the \(\delta^{13}\)C\({}_{\text{org}}\) composition of the CQS loess section during the warm-humid stage (MIS 3) (Figure 3).