## 5 Conclusion  
This is the first study to evaluate the vegetation recovery on a spatial and temporal basis in the five years following the Wenchuan earthquake. For a disaster event such as an earthquake, six aspects (_i.e._, altitude, fault zones, earthquake intensity, soil texture and vegetation types) are normally considered in analyses of vegetation recovery. Compared with previous studies, our study was comprehensive. We tried to include some important aspects for post-disaster assessment in this study, especially for vegetation recovery assessment after the earthquake. The Chinese government usually requires five years as a period for post-disaster reconstruction. This paper could be regarded as guidance for Chinese government departments whereby additional investment is needed for vegetation recovery.  
Even though [PERSON] [13], [PERSON] [19] and [PERSON] [23] studied vegetation damage and recovery following the Wenchuan earthquake, they did not provide methods for extracting vegetation damage areas. [PERSON] [13] used field survey data that required a long period of time and thereby affected the timeliness of disaster relief. This paper uses a mathematical method to rapidly extract vegetation damaged areas. In terms of the techniques and methods, our method is similar to those described in [14, 15, 16, 17, 21, 22]. We all use image difference technology. However, the referenced studies used experimental thresholds to extract vegetation damage areas. This approach is strongly subjective. For that reason, we have proposed a new method to numerically determine the threshold to extract vegetation damage areas with the goal of reducing the effect of human error and providing more objective and stable results. Using this method resulted in the recognition of 62.09% of the geological hazard points with MODIS data.  
The total area of vegetation damage from the Wenchuan earthquake was 475,688 ha, which accounted for 14.34% of our study area and was primarily distributed in the central fault zone, the southwest mountainous area and along rivers in the mid-west region of the study area. Vegetation recovery in damage areas was better in the northeast region of the study area, and in the western portion of the Wenchuan-Maoxian fracture; vegetation recovery was better with increasing altitude. The relationship between vegetation recovery and clay content in the topsoil is not obvious. The best vegetation recovery was for meadows and the worst recovery occurred in mixed coniferous broad leaved forests.  
The best vegetation recovery occurred in the northeast and southwest regions of the study area and was better in the mid-west region, but the worst recovery was in the central and eastern regions. After five years of recovery in the severely afflicted area, recovering vegetation accounted for 40% of the damaged areas. The vegetation will continue to primarily transform from vegetation with no recovery to vegetation that has largely recovered, but will never fully recover. Some areas such as southeast proportion of the study area and the mountains have a high proportion of vegetation with no recovery. Since the earthquake, there have been many landslides, debris flows and other geological hazards in the disaster area. A total of 81,338 ha of vegetation is undergoing degradation. This area of degradation accounts for 17.10% of the damaged area. These areas are mainly distributed on ridges or along rivers, and the main vegetation types are coniferous forest (31.39%) and scrub (34.17%). These areas needs to be studied as part of further research. In summary, approximately 41% of the vegetation in the damaged area recovered fully during the study period and it will take years to reach the vegetation level before the earthquake.