西藏林芝地区高等级公路生态袋边坡修复技术应用研究

Application study on ecological bag technology of restoring slope in high-grade highways in Nyingchi,Tibet

西藏公路建设快速发展的同时产生大量的公路边坡工程创面,且公路边坡修复的难度和投入巨大;因此,探索一种有效水土保持且能促进边坡植被修复的技术,对西藏公路建设中生态保护及生态修复具有重要的指导意义。本研究采用生态袋边坡修复技术,在林芝地区林拉高等级公路起始路段进行边坡与平地的植被修复对比试验。植被修复草种选用经高原地区引种驯化筛选出来的抗逆性极强的4种优良禾本科草种黑麦草(Lolium perenne)、高羊茅(Festuca elata)、草地早熟禾(Poa pratensis)、老芒麦(Elymus sibiricus)为供试材料,根据试验用沙壤土的饱和含水量(85%~90%)和当地作物施氮水平(0. 05~0. 10 g/kg),设计2个供水量水平(60%~70%,W1=60m L/kg,85%~90%,W2=85 m L/kg)和4个供氮量水平(N0=0 g/kg,N1=0. 027 8 g/kg,N2=0. 055 6 g/kg,N3=0. 083 3 g/kg)共8个处理,通过比较边坡和平地生态袋不同水氮供应条件下植被生长量和生物量变化,揭示该技术的植被修复效果及最佳水肥组合。结果显示:植被的生长发育明显受到生态袋水氮耦合效应的影响。在充分灌水低氮(W2N1)时,边坡植被的出苗率为79%、株高为4. 97~13. 70 cm、盖度为68. 33%~81. 67%、密度为1万3 600株/m2、地上生物量为0. 032 5 g/株,均达到最高水平;而平地植被在充分灌水中高氮(W2N2/N3)时,植株较高大,出苗率、盖度和密度均最高;但在低水无供氮(W1N0)时边坡和平地植被在出苗后期出苗率、高度、盖度均较低。此外,在2种灌水(W1W2)低氮(N1)时,边坡生态袋植被的出苗率、高度、盖度均较平地高。综上表明,生态袋具有明显的植被修复作用,且在某一特定的水氮耦合条件下,边坡植被修复效果比平地好。生态袋在边坡上植被修复最适水氮条件为:W2N1;平地上为:W2N2/N3。该技术适合在高原地区公路边坡植被修复中推广应用。

[Background]The rapid development of highway construction in Tibet has produced a large number of highway slope engineering wounds,naturally the difficulty and investment for the restoration of slope vegetation is huge. Therefore,to explore a slope vegetation restoration measures with strong soil and water conservation for the long-term stability has important guiding significance for ecological protection and ecological restoration in highway construction in Tibet. [Methods] The vegetation restoration experiment using ecological bags were conducted on the slope and flat land in the starting section of Lin La high-grade highways. The plants were Lolium perenne,Festuca elata,Poa pratensis,and Elymus sibiricus, all are of high resistance, domesticated and screened from plateaus. The experiment incorporated 2 irrigation levels( W1= 60 m L/kg and W2= 85 m L/kg) and 4 nitrogen levels( N0= 0 g/kg,N1= 0. 027 8 g/kg,N2= 0. 055 6 g/kg,and N3= 0. 083 3 g/kg) according to the saturated water content( 85%-90%) of sandy loam used in the experiment and nitrogen supply level( 0. 05-0. 10 g/kg) of local crops,for a total 8 treatments. By analyzing the change of vegetation growth and biomass under different water and fertilizer conditions for ecological bags,the effect of vegetation restoration( especially on a slope) and the best combination of water and fertilizer were obtained. [Results]The vegetation growth in ecological bags were affected by the coupling effect of water and nitrogen. When in full irrigation and low nitrogen,for example W2 N1,the seedling emergence rate was 79%,plant height was4. 97-13. 70 cm,coverage was 68. 33%-81. 67%,density was 13 600 plants/m2 and aboveground biomass was 0. 032 5 g/plant,slope vegetation reached the highest level. The seedling emergence rate,coverage,density of flat land vegetation were the highest with full irrigation,medium and high nitrogen( W2 N2/W2 N3). However,with low water and no nitrogen( W1N0),the seedling emergence rate,height and coverage of both slope and flat land vegetation were low in the later seedling emergence stage.In addition,the seedling emergence rate,height and coverage of slope vegetation were higher than those of the flat land with 2 levels of irrigation and low nitrogen( W1N1 and W2N1). [Conclusions]The vegetation growth needs a certain water and nitrogen content,but there is limited distribution in an environment with excessive or insufficient water or nutrients,which is closely related to their resistances.Ecological bags lead to a strong regulation performance of water and fertilizer and play a protective role on the slope. Under a certain water and nitrogen coupling condition,the growth of the vegetation on the slope is better than that of the flat land. Moreover,the optimal condition of water and fertilizer in slope vegetation restoration of ecological bags is that: W2N1;that in the flat land is: W2N2/W2N3. It can be concluded that this technology is suitable for the promotion and utilization of highway slope restoration in the tableland area.