## 3 Results
### Effect of Covering Purslane on the Wine Volatile Compounds  
Fifty-four and sixty-one aroma compounds were detected in the wines from both treatments in the years 2018 and 2019, respectively, as shown in Supplementary Tables S5 and S6. The compounds had all been grouped into eight categories according to the structure. Aroma profiles were presented as a fold change between the control and the treatment, and each category of clean tillage concentration was defined as 1. There were three categories of volatile compounds that were significantly affected by covering purslane in the year 2018 (Figure 9a). Covering purslane significantly increased the concentrations of norisoprenoids, acetate esters, and C6 alcohols. There were no significant differences between the treatments in the year 2019. CP increased the intensities of the herbaceous aroma, which was mainly from C6 alcohols. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Parameter**} & \multicolumn{1}{c}{**Treatment**} & \multicolumn{1}{c}{**Years**} & \multicolumn{1}{c}{**\(L\)**} & \multicolumn{1}{c}{**\(a\)**} & \multicolumn{1}{c}{**\(b\)**} & \multicolumn{1}{c}{**\(C\)**} & \multicolumn{1}{c}{**\(H\)**} \\ \hline Polyanthocyanins & Correlation & 0.196 & 0.862 * & 0.632 * & \(-\)0.331 & \(-\)0.879 * & \(-\)0.415 & \(-\)0.676 * \\  & \(p\) value & 0.541 & 0.000 & 0.027 & 0.294 & 0.000 & 0.179 & 0.016 \\ Monoanthocyanins & Correlation & 0.423 & \(-\)0.752 * & \(-\)0.731 ** & 0.529 & 0.666 * & 0.584 * & 0.354 \\  & \(p\) value & 0.170 & 0.005 & 0.007 & 0.077 & 0.018 & 0.046 & 0.259 \\ Flavonols & Correlation & 0.350 & 0.917 * & 0.738 ** & \(-\)0.556 & \(-\)0.833 * & \(-\)0.630 * & \(-\)0.521 \\  & \(p\) value & 0.265 & 0.000 & 0.006 & 0.060 & 0.001 & 0.028 & 0.082 \\ Flavanols & Correlation & \(-\)0.286 & \(-\)0.255 & \(-\)0.247 & 0.215 & 0.504 & 0.268 & 0.427 \\  & \(p\) value & 0.368 & 0.424 & 0.440 & 0.501 & 0.095 & 0.399 & 0.166 \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{Lightness (\(L\)); red-green color contribution (\(a\)); yellow-blue color contribution (\(b\)); chroma (\(C\)); and angular hue (\(H\)). * Significant correlation \(<\) 0.05 ** Significant correlation \(<\) 0.01 (bilateral).  
\end{table} 
Table 6: Pearson’s coefficient of vintage and treatments on wine flavonoids and colorimetric parameters. Figure 9: Influence of covering purslane on the aroma profiles and odor activity values (OAVs) in their wines. (**a**) aroma profiles in wines of the year 2018, (**b**) aroma profiles in wines of the year 2019; (**c**) OAVs of main aroma compounds (OAV \(>\) 0.1) in the year 2018; (**d**) OAVs of main aroma compounds (OAV \(>\) 0.1) in the year of 2019. * indicates significant differences between the wines of the control and covering purslane (\(p\) \(<\) 0.05, \(t\)-test). The aroma substances detected in the wines with odor activity values (OAVs) > 0.1 were selected and shown in Figure 9c,d. The odor activity value of each volatile compound was also calculated as the ratios of the concentration of an individual compound and its corresponding perception threshold [47]. The active aroma compounds were classed into seven groups according to their odor descriptors. Compared to the wines of clean tillage, covering purslane increased the floral aroma in their wines in the year 2018 (Figure 9c). Combined with wine volatile compounds, wines covering purslane were more abundant with norisoprenoids and esters than those of clean tillage in the year 2018. Norisoprenoids were derived from grapes and greatly contributed to the \"varietal aroma\" of some aromatic wines. However, they also contribute to the floral and fruity aromas of the wines directly or through synergistic effects [48]. Esters contribute to the floral and fruity aroma of wine, which can balance and harmonize various aroma substances in wine [49; 50]. Covering purslane significantly increased the intensities of floral aroma in the wines, which was mainly from norisoprenoids and eaters.