荒漠草原区油气管道建设对地表植被格局的影响

以油气管道经过的乌鲁木齐荒漠草原地区为研究对象,选择施工前、施工期以及恢复期3个不同施工阶段的遥感影像数据,解译地表植被类型,采用象元二分法提取植被覆盖度,通过比较时间上植被覆盖格局和土地利用格局的变化,分析油气管道建设对生态系统影响的范围和特点.研究发现:不同建设时期管道两边荒漠草原区土地利用类型差异较大,草地面积持续降低,共计减少32.53%,灌木林地面积增加到24.61%,建设用地面积在建设期增加,植被恢复期降低.研究区复杂程度提高,原有生态结构发生改变;建设期管道施工作业带及两侧10m范围内植被覆盖度显著低于其他区域,而管道两侧50~100以及100~200m范围内的植被覆盖度无明显差异,但与200~300m范围相比差异显著.管道建设主要影响范围为管道上方施工作业带以及两侧10m的范围内,间接影响范围为施工作业带两侧200m内;恢复期人为措施对研究区植被覆盖度的主要影响范围为施工作业带;管道建设改变了荒漠草原生态系统的组成结构,是管道周边土地利用类型和荒漠草地系统变化的主要推动力;人为恢复措施无法使受影响区域的植被恢复到建设前的水平.

The effect of pipeline construction on vegetation pattern in the desert steppe region

Desert steppe, as a fragile ecosystem, is easy to be influenced by human activities which may cause degradation. The typical desert steppe in the north of Urumqi was selected to study the impact of oil and gas pipeline construction. The land use types of different construction stages were obtained by remote sensing images interpretation, and dimidiate pixel model was used to extract vegetation coverage. Comparing the changes in vegetation cover pattern and landuse pattern, we can analyze the influence intensity and extent of oil and gas pipeline. The land use types varied greatly in different stages of construction. Grassland area decreased by 32.53%, while shrub land area increased to 24.61% from 2002 to 2010. Construction land area increases obviously in construction period, and declines after taking vegetation restoration measure. The study area became complicated, and original ecological structure changed. In construction period, vegetation coverage of buffer which is above the pipe and in 10m range was significantly lower than the surrounding areas, and which in 50~100m and 100~200m ranges were significantly different from that in 200~300m range. The main influence scope is the construction area with the range around 10m; the indirectly affect scope could reach 200m on either side of the pipeline. In vegetation-restoring period, construction area above the pipeline was the main influence scope. In conclusion, the oil and gas pipeline construction is the main driving force on the land use types change in desert steppe which is cut up by pipeline. Artificial restoration measures could hardly rehabilitate the vegetation of the influenced area as the same as it was used to be.