## 3 Results  
### Spatial and Temporal Variations of Vegetation in the MHRB  
In the MHRB, the mean annual LAI from 2001 to 2018 ranged from 0.14 and 3.15 m\({}^{2}\) m\({}^{-2}\), and its mean annual GPP ranged from 121.89 and 1306.82 gC m\({}^{-2}\) yr\({}^{-1}\) (Figure 3). Higher values of LAI and GPP were concentrated in the central and southern portions of the MLHRB, the MBSHRB, the north of MDQHRB, the central regions of the MZYHRB, and the northern and southern regions of the MZWHRB. At a regional level, the MHRB's mean annual LAI and GPP were 0.88 m\({}^{2}\) m\({}^{-2}\) and 666.61 gC m\({}^{-2}\) yr\({}^{-1}\) from 2001 to 2018, respectively (Table 2). Sub-basins could be graded in accordance with the mean  
Figure 2: The spatial distribution of underlying driving factors in the MHRB. Temperature (**a**), precipitation (**b**), humidity index (**c**), VPD (**d**), ETO (**e**), solar radiation (**f**), elevation (**g**), slope (**h**), aspect (**i**), land use (**j**), landform (**k**).  
annual values of LAI and GPP as follows: MBSHRB > MLHRB > MZWHRB > MDQHRB > MZYHRB > MYDHRB. The MBSHRB had the maximum vegetation coverage, with mean annual LAI and GPP values of 1.17 m\({}^{2}\) m\({}^{-2}\) and 791.41 gC m\({}^{-2}\) yr\({}^{-1}\), respectively. Mean annual LAI and GPP values in the MYDHRB were the lowest, which were 0.57 m\({}^{2}\) m\({}^{-2}\) and 490.7 gC m\({}^{-2}\) yr\({}^{-1}\), respectively.  
Annual LAI values in the MHRB showed a significantly upward trend with the rate of 0.017 m\({}^{2}\) m\({}^{-2}\) yr\({}^{-1}\) (\(p\) < 0.01), increased from 0.7 m\({}^{2}\) m\({}^{-2}\) to 1.02 m\({}^{2}\) m\({}^{-2}\) (Figure 4a). Annual GPP values in the MHRB increased with a rate of 12.95 gC m\({}^{-2}\) yr\({}^{-2}\), going from 501.21 gC m\({}^{-2}\) yr\({}^{-1}\) in 2001 to 782.46 gC m\({}^{-2}\) yr\({}^{-1}\) in 2018 (\(p\) < 0.01) (Figure 4b). From 2001 to 2018, 95.17% of the regions in the MHRB showed increasing trends in LAI, while 81.4% of the regions exhibited significantly growing trends (\(p\) < 0.05), and 98.27% of the areas exhibited increasing trends in GPP, while 91.5% of the areas showed significantly upward trends (\(p\) < 0.05) (Table 3; Figure 5). The change rates for LAI and GPP varied in different regions, ranging from \(-\)0.07 to 0.14 m\({}^{2}\) m\({}^{-2}\) yr\({}^{-1}\) and \(-\)51.16 to 47.04 gC m\({}^{-2}\) yr\({}^{-2}\), respectively (Figure 6). The increase rates of LAI and GPP were higher in the MBSHRB, the central part of the MLHRB, the north of the MDQHRB, the central part of the MZYHRB, and the central and western portions of the MZWHRB. The areas with lower change rates were mainly distributed in the north and south of the MLHRB, the northwest of the MYDHRB, and the east of the MZYHRB and MZWHRB.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Region** & **LAI (m\({}^{2}\) m\({}^{-2}\))** & **GPP (gC m\({}^{-2}\) yr\({}^{-1}\))** \\ \hline MHRB & 0.88 & 666.61 \\ MLHRB & 1.06 & 740.64 \\ MBSHRB & 1.17 & 791.41 \\ MYDHRB & 0.57 & 490.7 \\ MDQHRB & 0.89 & 707.48 \\ MZYHRB & 0.8 & 654.27 \\ MZWHRB & 0.91 & 720.77 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mean annual LAI and GPP values in the MHRB from 2001 to 2018.  
Figure 3: Spatial distribution of mean annual LAI **(a)** and GPP **(b)** in the MHRB from 2001 to 2018.  
Figure 4: Change trends for LAI (**a**) and GPP (**b**) in the MHRB from 2001 to 2018.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Change Trends** & **LAI** & **GPP** \\ \hline \hline \begin{tabular}{c} Insignificant decrease \\ Significant decrease (\(p<0.05\)) \\ \end{tabular} & \
\begin{tabular}{c} 3.59 \\ 1.24 \\ 4.83 \\ 13.77 \\ 81.4 \\ 95.17 \\ \end{tabular} &
\begin{tabular}{c} 1.35 \\ 0.39 \\ 1.73 \\ 6.76 \\ 91.5 \\ 98.27 \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 3: Proportion of areas with different vegetation change trends in the MHRB from 2001 to 2018 (%).  
Figure 5: Spatial distribution of vegetation change trends for LAI (**a**) and GPP (**b**) in the MHRB from 2001 to 2018.