## 5 Discussion
### Effects of Extreme Climate on Different Vegetation Types  
According to the factor analysis, the extreme precipitation factors RX1d and RX5d make a significant contribution to the overall Tarim Basin EQI. The EQI of forests, grasslands, desert vegetation, and agricultural vegetation are most impacted by the extreme precipitation indices. Although the shrub EQI is most affected by the SU25, the extreme precipitation factors of SDII, RX1d, and RX5d also make significant contributions to the shrub EQI. Overall, precipitation exerts a larger influence on vegetation than temperature, which corresponds to the discoveries of [PERSON] and [PERSON] [87; 88]. However, single-factor extreme climate analysis is no longer sufficient for fully assessing the influence of extreme climate upon vegetation. Additional examination is required to comprehend the combined impacts of extreme climate on vegetation [13]. The results of the interacting-factor analysis indicate that the interplay between any two extreme climate factors exceeds the impact of a single factor. This means that the EQI spatial distribution is affected by the interaction of various factors that have an influence. We found that the combined effect of the TX10P \(\cap\) TNn has the greatest impact on shrubs and grasslands. Most shrubs grow near riverbanks and are primarily _Tamarix ramossissima_. Their growth requires not only heavy rainfall but also depends on groundwater [89]. Especially in summer, the combined effect of the TX10P and TNn can reduce soil water evaporation in arid areas, maintain soil moisture, and increase the available water for vegetation transpiration. On the other hand, it can reduce vegetation transpiration during the day and increase the net photosynthetic rate of vegetation during high temperatures, thereby promoting vegetation growth. Within the forest, the _Populus_equhratica_ is the main tree species, primarily distributed within the Tarim River Basin. Its water requirements for growth mainly depend on the river and groundwater [90]. The combined effect of the TN90P and SU25 contributes the most to the forest EQI. Higher daytime temperatures can not only promote vegetation photosynthesis but also contribute to glacier and snow melting. The melting of these due to high temperatures can supplement river flow and provide water resources for vegetation [91; 92]. Higher nighttime temperatures can alter and promote vegetation growth, primarily through lessening frost. It may also be related to the phenomenon of overcompensation. Studies have found that, under sufficient soil moisture and nutrient conditions, higher nighttime temperatures enhance leaf respiration. This leads to a faster consumption of leaf carbohydrates and stimulates compensatory photosynthesis the following day [93]. As a result, vegetation growth is promoted.  
The contribution of the single factor TX90P to desert vegetation growth is low, but its interaction with RX5d, the precipitation factor, prominently promotes the desert vegetation growth. This suggests that the desert vegetation distribution is primarily affected by precipitation [94; 95]. Conditions of precipitation provide the necessary moisture for the growth of vegetation in the desert. Higher daytime temperatures can promote photosynthesis and extend the growth period of vegetation [43; 88]. For example, the vegetation index in autumn responds slightly more to temperature than to precipitation, and higher temperatures can delay the autumn growing season [96]. The growth of agricultural vegetation is more influenced by human factors, including irrigation and mulching. Therefore, extreme climate has a relatively small impact on agricultural vegetation. The interaction between the TN10P and TNn has the greatest impact on the growth of agricultural crops. This is achieved by reducing soil evaporation to maintain a balance between the available water and the vegetation. Additionally, the TN10P can also suppress vegetation respiration, thereby reducing the consumption of dry matter.