# Impact of Natural and Human Factors on Dryland Vegetation in Eurasia from 2003 to 2022
## 4 Discussion  
In recent decades, vegetation activity in the Eurasian drylands has undergone significant changes driven by natural factors such as temperature, precipitation, soil moisture, atmospheric vapor pressure deficit and terrestrial water storage [6; 56; 57]. The prominent role of the Eurasian drylands in the global ecosystem necessitates a more in-depth understanding of the changing trends in vegetation activity in this region under the backdrop of global natural change [6; 30]. This study, combining various indices reflecting vegetation activity, comprehensively analyzed the changing trends in vegetation greenness (represented by NDVI), productivity (represented by GPP) and photosynthetic capacity (represented by SIF) in the Eurasian drylands over the past two decades. Consistent with previous research results, overall, vegetation greenness and productivity in the Eurasian drylands show a significant increasing trend [4]. Furthermore, this study reveals that the photosynthetic capacity of vegetation in the Eurasian drylands generally exhibits a significant upward trend, with the proportion of areas showing a significant increase reaching 41.90%. Additionally, the study unveils a distinct spatial pattern in the changing trends in vegetation activity in the Eurasian drylands, with South Asia, East Asia, West Siberia and the Mediterranean region experiencing a much higher degree of enhancement in vegetation activity compared to other regions. In contrast, Central Asia showed trends in browning, which is similar to the results of [PERSON] et al. [58]. The spatial differences emphasize the importance of considering regional-specific factors when assessing vegetation activity and analyzing influencing factors in the Eurasian drylands. In this study, the impact of five natural factors, including temperature, precipitation, soil drought, atmospheric drought and terrestrial water storage, on vegetation activity in the Eurasian drylands was quantified, with a further analysis of their regional specificity. Previous studies have indicated that the vegetation variability in the Eurasian drylands are primarily influenced by MAP, whereby an increase in MAP can improve SM and promote vegetation greening [30; 59; 60]. However, [PERSON] et al. [60] reported that precipitation \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variables** & & & **Cropland (\%)** & **Grassland (\%)** \\ \hline \multirow{8}{*}{NDVI} & \multirow{4}{*}{Improvement} & double & 7.42 & 6.46 \\  & & natural & 8.69 & 5.49 \\  & & human & 9.92 & 10.07 \\  & & double & 8.40 & 8.71 \\  & & natural & 11.29 & 8.85 \\  & & human & 6.33 & 8.38 \\  & & double & 11.22 & 9.30 \\  & & natural & 9.94 & 3.93 \\  & & human & 12.55 & 14.35 \\ GPP & & double & 9.77 & 8.41 \\  & & natural & 86.90 & 4.43 \\  & & human & 4.62 & 4.58 \\  & & double & 18.02 & 14.72 \\  & & natural & 1.18 & 0.24 \\ SIF & & human & 10.62 & 8.96 \\  & & double & 16.07 & 15.24 \\  & & natural & 0.88 & 0.40 \\  & & human & 2.97 & 10.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The pixel ratio of driving factors. “Improvement” represents an increasing trend in vegetation over the past 20 years, while “Degradation” indicates a declining trend in vegetation over the same period. “Double” is the contributions of natural and human factors to vegetation, “natural” represents the contributions of natural to vegetation, and “human” indicates the contributions of human to vegetation. explains variability in dryland vegetation greenness globally but not locally. [PERSON] et al. (2019) argued that the dynamics of global dryland vegetation were more sensitive to soil moisture. This study validates this point and reveals that, compared to atmospheric drought and terrestrial water storage, soil moisture has a greater impact on vegetation activity in the Eurasian drylands. The shallow root systems of vegetation greening (grassland and cropland) make them more susceptible to changes in available water.