# Satellite-Observed Global Terrestrial Vegetation Production in Response to Water Availability
## 3 Results
### Spatio-Temporal Dynamics of Vegetation Productivity's Response Time to Water Availability  
We analyzed the temporal and spatial dynamics of vegetation productivity's response time of to water availability changes further. Productivity's response time to water availability is defined as timescales over which the maximum GPP-SPEI correlations are recorded. It can be seen from the spatial distribution of productivity's response time to water availability (Figure 4b) that the response time of 56.8% of the global terrestrial ecosystems to water resources is based primarily on short-term and medium-term time scales. In Canada, Northwestern Colombia, Eastern Russia, and Northeastern and Southeastern China, the response time of vegetation productivity to SPEI is relatively long, typically more than 12 months. The longer the response time to water availability changes, the stronger the ability of vegetation productivity in these areas to withstand long-term water shortages. Seasonal changes also affect the length of time in which GPP responds to SPEI in different regions. It can be seen from Figure S3e-h that 34.92% of the global terrestrial ecosystem GPP requires a long time to respond to SPEI during the period from March to May and is concentrated largely in the mid-high latitudes of the Northern hemisphere. With the passage of seasons, the proportion of GPPs in these high latitude regions with a longer response time to SPEI decrease gradually from June to November. From December to November of the following year in Australia, GPP's response time to SPEI changes from a short-term time scale (less than 6 months) to a medium- and long-term time scale (6-9 months).  
As shown in Figure 5b, an analysis of the changes GPP's in the response time to SPEI in various climate zones indicates that as the climatic conditions become gradually humid, the response time of vegetation productivity to changes in water availability increased (GPP's mean response time to SPEI extended from 3.9 months to 8.9 months). The characteristics were consistent in different seasons, indicating that vegetation's productivity capacity to withstand long-term water shortages is weaker in arid and semiarid areas than in humid and semi-humid areas. By comparing GPP's response time to SPEI under different land cover types (Figure 6b), it can be seen that DNF has the strongest ability to resist long-term water shortages (the mean response time reached 13.6 months), followed by OS, EBF, WET, CRO, ENF, WSA and MF (mean response time of 9.9, 8.5, 8.4, 8.1, 7.9, 7.8 and 7.5 months, respectively). SAV, GRA, and DBF have poor ability to resist and mitigate drought (mean response time of 6.1, 6, and 4.9 months, respectively). It is worth noting that the land cover types that are more relevant to water availability are often accompanied by weak drought resistance.  
Figure 6: The correlation coefficient (**a**) and response time (**b**) of vegetation productivity to water availability in different land cover types. ENF, EBF, DNF, DBF, MF, OS, WSA, SAV, GRA, WET and CRO represent evergreen needleleaf forest, evergreen broadleaf forest, deciduous needleleaf forest, deciduous broadleaf forest, mixed forest, open shrulands, woody savannas, savannas, grasslands, wetlands and croplands, respectively. Boxes represent interquartile ranges of the values of 25 th and 75 th percentiles (Q\({}_{\text{2S}}\), Q\({}_{\text{7S}}\)), whiskers cover Q\({}_{\text{2S}}-1.5\times\) (Q\({}_{\text{7S}}-\) Q\({}_{\text{2S}}\)) to Q\({}_{\text{7S}}\)\(1.5\times\) (Q\({}_{\text{7S}}-\) Q\({}_{\text{2S}}\)), horizontal lines represent the median, black empty squares represent the mean, and black solid diamonds indicate outliers.