汶川地震重灾区生态系统碳储存功能空间格局与地震破坏评估

通过建立汶川地震灾区碳储存功能评估指标体系,利用ArcGIS平台计算了灾区四大碳库(地上部分碳、地下部分碳、死亡有机碳和土壤碳)碳储存密度,分析了碳储存空间格局和规律.结果表明:灾区碳储存总量3.97×108t,平均碳密度52.2t/hm2,其中亚高山常绿针叶林碳密度和碳储存最高.碳储存量随坡度增加而增加,大于35.地区碳储存量达1.3×108t,占灾区碳存总量的33.9％.碳储量随海拔增加呈现波动的曲线,0-750m区域碳储量随海拔增加而增加,在750-1750m区域段碳储量因地震对植被的破坏出现下降,然后又随海拔增加而增加,到3250m时出现碳储存量高峰,储碳量达7273t,之后又逐渐下降.此外,通过对比地震前后灾区生态系统碳储存功能得出研究区生态系统碳储存功能总体减少为9.98×106t,而地震对碳储存功能的影响主要是植被破坏导致的碳储存降低,其中退化最严重的地区在彭州和什邡的北部山区,并沿龙门山向西南方向延伸.研究结果直观反映了灾区碳储量空间格局,为决策者实施破坏区植被恢复策略以及地震灾区碳管理等提供依据.

Spatial distribution of carbon storage function and seismic damage in wenchuan earthquake stricken areas

The value of terrestrial ecosystem carbon sequestration services has been widely recognized. Forests, grasslands and other ecosystems can store large amounts of carbon, which is the key to mitigating global climate change. The eco-environment of the western region of Sichuan Province was greatly destroyed by the earthquake which had occurred in Wenchuan on May 12, 2008. One of the direct impacts is that the landscape was seriously damaged and the disturbed eco-system released a significant amount of carbon dioxide because of sudden changes inland utilization and vegetation cover. Our goal was to use the maps of land use and land cover types and data of carbon reserves stocks in four carbon pools to estimate the amount of carbon stored in a landscape currently and the pre-seismic amount of carbon in the earthquake-hit areas, and then we have got a series of maps which can help us to conduct carbon management. Based on the geographical information system software of ArcGIS, this paper presented the evaluation index system to assess the carbon storage function of the earthquake-hit area, by calculating the density of carbon storage for four carbon pools (aboveground biomass, underground biomass, soil carbon and dead organic matter) in each grid. In addition, this paper also analyzed the spatial pattern of carbon storage function in this area. The results showed that the total carbon storage volume of the earthquake-hit area is 3.97×10⁸ t based on the spatial analysis module of ArcGIS and the average carbon density is 52.2 t/hm². The ecosystem with the highest carbon storage and carbon density is represented by subalpine evergreen coniferous forest. The carbon storage volume increased with the increasing slope gradient and altitude. The carbon storage volume in the area where the slope is greater than 35°is 1.3×10⁸ t, accounts for 33.9% of the total carbon storage volume in the earthquake-hit area. Because of the forests was destroyed by the powerful earthquake, the function of carbon storage presents a suddenly drop sat altitude of 750-1750m. In addition, the impact of earthquakes on the carbon storage is that the carbon stocks lowered primarily owing to vegetation damage, with the overall reduction reaching 9.98×10⁶t. The most severely degraded areas are located in the northern mountains of Pengzhou County and Shifang County, along the southwestward extension of the Longmen Mountain. The recommendations of post-disaster reconstruction, vegetation and carbon management are listed as follows. 1) Expanding the area of forest coverage and improving forest quality is a key point to play an important role in forest carbon storage. 2) The vegetation restoration in the earthquake-hit area is given priority to the natural restoration approach of forest reservation, complementary with artificial approaches, such as artificial reforestation and landslide engineering control measures. The risk of secondary disasters can be decreased while ecosystem carbon storage function of the destroyed area is reconstructed. 3) To enhance the carbon contributions of farmland and grazing land area by pushing no-tillage agriculture, developing ecological agriculture, establishing a series of measures to improve comprehensive utilization (e. g., taking the action of returning straw to the field instead of burning them), and strengthening the carrying capacity control of prairie areas. Our results will help guide the vegetation recovery, carbon management and carbon trading. But most importantly, they can support a series of decisions made by government sat various levels in the earthquake-hit areas.