## 2 Materials and Methods
### Data Sources and Processing  
#### 2.3.1 Land-Use and Land-Cover Change Data and Processing  
This study utilized the Global 30 m Land-Cover Dynamics Monitoring Product (GLC_FCS30D), developed by the research team led by [PERSON], as the primary data source ([[https://data.casearth.cn/](https://data.casearth.cn/)]([https://data.casearth.cn/](https://data.casearth.cn/)), accessed on 10 October 2024). The dataset integrates continuous change detection technology and Landsat imagery to capture the temporal points of pixel changes accurately. Updates are conducted using high-confidence, globally distributed training samples [38]. The dataset updates employ local adaptive classification models and temporal consistency optimization algorithms to enhance temporal stability, with rigorous validation applied to the results. Within the basic classification system (comprising 10 major land-cover types), the dataset achieved an overall accuracy of 80.88% (\(\pm\)0.27%). For the Level 1 classification system (including 17 land-cover types), the accuracy was 73.04% (\(\pm\)0.30%). This study analyzed grassland conversion in the HBO region using land-use/land-cover data from three key years: 2000, 2010, and 2020. Based on the land-use type definitions given by [PERSON] et al. [39], land-cover types in this study were categorized into six primary classes: cropland, forestland, grassland, bare land, water bodies, and impervious surfaces. Detailed classification results are presented in Table 1.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Basic Classification System** & **Level 1 Validation System** & **Fine Classification System** & **ID** & **Description** & **Merged Category** \\ \hline \multirow{4}{*}{Cropland} & \multirow{2}{*}{Rainfed cropland} & Rainfed cropland & \(10\) & & \\ \cline{3-6}  & & Herbaceous cover cropland & \(11\) & Land on which crops are grown & Cropland \\ \cline{2-6}  & & Irrigated cropland & Irrigated cropland & \(20\) & & \\ \hline \multirow{4}{*}{Forest} & Deciduous broadleaved forest & Open deciduous broadleaved forest & \(62\) & & \\ \cline{2-6}  & & Closed overgreen needle-leaved forest & \(71\) & Refers to the growth of trees, shrubs, bamboo, coastal mangrove forests and other forestry land & Forest \\ \cline{2-6}  & & Open overgreen needle-leaved forest & \(72\) & \(82\) & & \\ \cline{2-6}  & & Deciduous needle-leaved forest & Open deciduousleaved forest & \(82\) & & \\ \hline Shrubland & Shrubland & Shrubland & \(120\) & & & \\ \hline \multirow{4}{*}{Grassland} & \multirow{4}{*}{Grassland} & \multirow{4}{*}{Grassland} & \multirow{4}{*}{130} & \multirow{4}{*}{\(5\%\), including grassland, sparsely forested grassland with a canopy of less than \(10\%\)} & \multirow{4}{*}{Grassland} \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & & Bare areas & \(200\) & Land that has not yet been used, including land that is difficult to use & \\ \cline{2-6}  & & Unconsolidated bare areas & \(202\) & & \\ \hline \multirow{2}{*}{Wetland} & \multirow{2}{*}{Inland wetland} & Marsh & \(182\) & & \\ \cline{2-6}  & & Flooded flat & \(183\) & Refers to natural land waters and water conservancy facilities & Waterbody \\ \hline Waterbody & Waterbody & Waterbody & \(210\) & & & \\ \hline \multirow{2}{*}{Impervious surface} & \multirow{2}{*}{Impervious surface} & \multirow{2}{*}{Impervious surface} & \multirow{2}{*}{190} & \multirow{2}{*}{Refers to urban and rural residential areas and other industrial, mining, transportation, and other land} & \multirow{2}{*}{Impervious surface} \\ \cline{1-1} \cline{5-5}  & & & & & \\ \hline \end{tabular}
\end{table}
Table 1: Descriptions of land-use classification and reclassification.