西南地区道路建设对植被净初级生产力的影响

道路建设促进区域社会经济发展的同时,通过直接改变原有生态系统、间接增强人类活动进而改变原有生态系统的途径对周围生态系统产生影响。定量评估道路建设对植被净初级生产力(Net Primary Productivity,NPP)的影响对掌握线性工程生态环境影响,进行社会经济发展与生态安全权衡具有一定现实意义。基于西南地区2016年道路和2015年NPP数据,利用核密度(Kernel Density,KD)表征道路影响域和影响强度,借助ArcGIS平台,分析不同土地覆被和经济发展强度下道路建设与NPP的关系。结果表明:(1)搜索半径为0.5km时,道路KD (km/km²)范围为[0.0,47.3],其中道路KD为零的区域约占研究区总面积的79.8%,这些未受道路干扰区域大部分位于西藏、青海、四川西部、贵州和云南的西北部;道路KD为(0.0,5.0]的区域约占道路KD非零区域面积的88.4%,除成都、重庆、贵阳、南宁、昆明等城市外,区域大部分地区道路密度仍处于较低水平。(2)从不同土地覆被下道路KD与NPP的关系来看,中低道路干扰条件下,林地、耕地和人工表面稳定性更强,道路KD小于4.1时NPP相对稳定,而草地、湿地和其他土地覆被在道路KD大于2.1后,NPP出现急剧变化。随道路KD增大NPP趋于发散,这可能是由道路密度增加后其两侧人类干扰类型多样化引起。(3)以县级行政区划为单位,按单位面积道路KD由小到大的顺序,将研究区分成5个部分:分区1-分区5。在分区1,NPP随道路KD增大呈先波动升高,相对稳定变化后降低再发散;在分区2-分区5,NPP随道路KD增大总体呈降低趋势,且变异性逐渐增加,经历了相对稳定阶段、线性变化阶段、发散阶段。根据研究结果,道路建设需重点关注生态敏感脆弱区的植被保护,如草地和湿地,应尽量避免较高密度道路建设带来的生态系统退化问题,同时应根据不同的地区制定适宜的保护方案。

Influence of road construction on vegetation net primary productivity in southwest China

While road construction should facilitate regional socio-economic development,it also imposes impact on the surrounding ecosystem by directly changing the original ecosystem and indirectly enhancing the intensity of human activities.Quantitative assessment of the road construction impact on the net primary productivity (NPP) of vegetation has a certain practical significance for grasping the ecological and environmental influence of linear engineering and weighting the socio-economic development and ecological safety.Based on the road data of 2016 and NPP data of 2015 in southwest China,this study used kernel density (KD) to represent the road-effect zone and influence intensity and analyzed the relationship between road construction and NPP under different land cover and economic development intensity with the help of ArcGIS platform.The results show that:(1) when the search radius is 0.5 km,the road KD ranges from 0.0 to 47.3,and the areas where road KD is zero account for around 79.8% of the total research area.Most the undisturbed areas are located in Tibet,Qinghai,and western Sichuan,Guizhou,and northwest Yunnan.The areas where road KD ranges from 0.0 to 5.0 account for around 88.4% of the non-zero road KD areas.Except for cities such as Chengdu,Chongqing,Guiyang,Nanning,and Kunming,the road density in most regions are still at a low level.(2) In terms of the relationship between road KD and NPP under different land cover,forestlands,croplands and built-up lands are more stable under low and medium road disturbance conditions,and NPP is relatively constant when road KD is less than 4.1.However,NPP has changed sharply under the land cover types of grasslands,wetlands and others when road KD is greater than 2.1.With the increase of road KD,NPP tends to diverge,which may be caused by the diversification of different human disturbances on both sides of the road with the increase of road density.(3)Take county administrative divisions as units,the research is divided into 5 zones according to the road KD of per unit area,which gradually increases from zone 1 to zone 5.In zone 1,the NPP increases volatility with the change of road KD,and then decreases and diverges after the relatively stable change;In zone 2 to zone 5,with the increase of road KD,NPP generally shows a decreasing trend,and its variability increases gradually,and it has gone through three stages:relative stability,linear change and divergence.According to the results of this study,road construction should focus on the protection of vegetation in ecologically sensitive and vulnerable areas,such as grasslands and wetlands,and avoid the degradation of the ecosystem caused by high-density road construction as much as possible,and formulate appropriate protection schemes according to different regions.