## 5 Conclusions  
In this study, we explored the NPP and ET dynamics of the arid ecosystem in Tianshan North Slope under RCP2.6, RCP4.5, and RCP8.5 by using AEM. The climate in Tianshan North Slope will experience a wetter and warming trend from 2006 to 2055 under each RCP scenario. In response to the changes in climate and CO\({}_{2}\) concentration, the regional mean annual NPP increases by a rate of 1.16, 1.62, and 2.15 g C m\({}^{-2}\) year\({}^{-1}\) under RCP2.6, RCP4.5, and RCP8.5, respectively. Similar to the regional mean annual NPP, the regional annual ET presents an increasing trend with the rate of 0.38 mm year\({}^{-1}\) under RCP2.6, 0.43 mm year\({}^{-1}\) under RCP4.5, and 0.52 mm year\({}^{-1}\) under RCP8.5. Hence, for the entire region, the Tianshan North Slope will benefit from the changes during 2006-2055. The spatial pattern of the climate change indicates that the temperature in the basin increases while it decreases in the mountains from 2006 to 2055, although the decreased area in the mountains region decreases from RCP2.6 to RCP8.5. The annual precipitation in the northeastern part of the study area presents a declining trend under RCP2.6 and RCP4.5, and the precipitation in the mountains increases much more than in the other regions. However, the spatial patterns of regional annual NPP difference under different RCP scenarios show that the increase of NPP mainly occurs in the central and western part where the CRP is abundant. The decline in regional annual NPP mainly occurs in the northeastern part under RCP2.6. The spatial patterns of regional ET difference indicate that the increase of ET mainly occurs in the central and western part, which is similar to those of the NPP difference. However, the ET decreases in the high mountains, which is mainly caused by the decline in temperature. The decline of ET in the northeast part is mainly induced by the decline in precipitation under the RCP2.6 scenario. There is temporal heterogeneity in the climate patterns, in which the climate changes more rapidly in the first 30 years (2006-2035) than in the next 20 years (2036-2055) under each RCP scenario. Except the declining trend of precipitation in the next 20 years under RCP4.5, the increasing trends are found for precipitation and temperature in each study period under all three RCP scenarios. In response to the heterogeneity of the climate change, the increase rates of NPP and ET in the first 30 years are higher than those in the next 20 years under each RCP scenario. Moreover, the ET decreases in the next 20 year under RCP4.5 and RCP8.5, and the NPP decreases by a rate of 0.75 g C m\({}^{-2}\) year\({}^{-1}\) in the next 20 years under RCP4.5. The sensitivity of different vegetation types is well analyzed in this study. We find that different vegetation types respond differently to the changes in climate and CO\({}_{2}\) concentration under different RCP scenarios. All vegetation types in Tianshan North Slope experience increased NPP and ET with various rates under each RCP scenario. Under each RCP, the NPS, PS, and GRS are more sensitive to the changes in climate and CO\({}_{2}\) concentration compared to the other vegetation types, while those of the TBF and CRP are less sensitive to the changes. The sensitivity of the different vegetation types varies during different study periods and under different RCP scenarios. However, the WUE of each vegetation type shows an increasing trend under all RCP scenarios. For each vegetation type, the increasing rate of WUE increases from RCP2.6 to RCP8.5, resulting from the warm and wet climate change and increasing CO\({}_{2}\) concentration. Conceptualization, C.L., G.L. and P.C. ; methodology, C.Z. and P.C. ; software, C.Z. ; validation, C.Z., C.L. and G.L. ; formal analysis, P.C. ; investigation, P.C. ; resources, S.C., L.D.C., R.D.T., S.T. and P.C. ; data curation, S.C., L.D.C., R.D.T., S.T. and P.C. ; writing--original draft preparation, P.C. ; writing--review and editing, P.C., C.L., S.T. and F.U.O. ; visualization, P.C. ; supervision, G.L., P.T.