## 5 Conclusions  
This study examined the GGP-driven land use and land change in the first round of the GGP, and assessed its effects on ecosystem services. We then demonstrated alternative trajectories of afforestation patterns to analyze their potential impacts on ecosystem services by a comparison to the actual changes. Our study indicates that the GGP promoted the concerned ecosystem services, but this improvement would be more efficient by optimized afforestation locations. The choice for afforestation types also impacted the ecosystem services and their trade-offs. The arising lessons and recommendations for the GGP are as follows:  
1. The GGP drove a significant change of land-use/land-cover from 2000 to 2015, and all the concerned regulating services increased. Most farmlands were converted to forests in a relatively flat area, whereas steep-sloped farmlands, the primary target of the GGP, were not received enough attentions in the first around of the GGP.
2. The GGP-driven improvements in regulating services strongly depend on the afforestation locations. Prioritizing the conversion of steep-sloped and riparian farmlands can cost-effectively promote flood mitigation, water purification, and soil retention services as compared with current level in 2015. Conversing steep-sloped farmlands to forests can promote better in soil retention and flood mitigation services, whereas conversing of riverain farmlands to forests can more efficiently promote water purification service. We recommend that riverain farmlands should be considered for conversion to forests for a headwater region in the new round of the GGP.
3. The trade-offs between provisioning service and regulating services closely associates with afforestation types. A high proportion of economic forest increased non-timber product provisioning service, but at the expense of significant decreases in the concerned regulating services. The tradeoffs were enhanced when planting economic trees in ecological prioritizing areas that can provide high regulating service levels but a low provisioning service. We identified a suitable scenario (the proportion ranges 50-60%) that would reduce these trade-offs. Therefore, we do not recommend the unrestricted proportion of economic forest of the new policy of the second round of the GGP. The GGP management strategies should be proposed though deliberate efforts, accounting for afforestation types and their spatial allocation.  
The following are available online at [[http://www.mdpi.com/2071-1050/12/11/4762/s1](http://www.mdpi.com/2071-1050/12/11/4762/s1)]([http://www.mdpi.com/2071-1050/12/11/4762/s1](http://www.mdpi.com/2071-1050/12/11/4762/s1)), Table S1: Detailed information on the main input parameters of the main GGP-related land use types and their sources in the InVEST model. Table S2: Comparison of annual average water yield between observed values and simulated values  
Conceptualization, X.L. and T.G.; methodology, Y.T., J.Z. and T.G.; formal analysis, S.L., Y.T., X.Z., D.Z., L.Y., L.J. and T.G.; investigation, L.Y., X.L., Y.T. and L.J.; writing, X.L., Y.T. and T.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19030204, XDA19050502), the National Key Research and Development Program of China (2016 YED600206) and the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (QYZDJ-SSW-DQC027).  
We thank members of sampling team of Agronomy College, Shenyang Agricultural University ([PERSON], [PERSON] and [PERSON]). We would be grateful to [PERSON] of the Department of Natural Resources of Qingyuan Manchu Autonomous County for providing the local statistical data of the Grain-for-Green Program.  
The authors declare no conflict of interest.