若尔盖沙化草地不同生态恢复模式土壤活性有机碳及碳库管理指数变化

研究退化林草地不同生态恢复模式土壤活性有机碳和碳库管理指数变化,可为评价生态恢复措施提升土壤质量的效果,以及优化生态恢复模式的选择提供重要参考。结合野外调查和室内分析法,研究了若尔盖沙化草地不同生态恢复模式土壤有机碳组分及碳库管理指数变化。若尔盖沙化草地的生态恢复模式有:灌草间作模式Ⅰ(条带状红柳间植草本植物,SGⅠ)、灌草间作模式Ⅱ(环状红柳间植草本植物,SGⅡ)、沙障+灌草模式(红柳沙障+红柳间植草本植物,SBSG)。结果表明,与沙化草地(DG)相比,3种恢复模式都能提高土壤有机碳及其活性组分含量。SGⅠ模式的全剖面土壤微生物量碳(MBC)、溶解性有机碳(DOC)、易氧化有机碳(EOC)、颗粒有机碳(POC)含量分别增加36.6%、139.0%、89.4%、130.9%;SGⅡ模式的分别增加2.7%、-43.9%、15.0%、49.7%;SBSG模式的分别增加82.4%、21.8%、56.2%、170.3%。表明SGⅠ与SBSG提高土壤有机碳的效应相近,而且二者都远大于SGⅡ。3种生态恢复模式土壤活性有机碳分配比例与DG的差异表现不一致,显著体现是SGⅠ模式土壤DOC分配比例的垂直变化出现分馏现象。3种生态恢复模式土壤碳库管理指数(CPMI)均大于100%,能不同程度地提升土壤质量,其效应大小为SGⅠSGⅡSBSG。易氧化有机碳可作为反映沙化草地生态修复模式土壤质量变化的优选指标,CPMI也可用于表征生态恢复措施提升沙化草地土壤质量的效果。

Effects of different ecological restoration patterns on labile organic carbon and carbon pool management index of desertification grassland soil in zoige

The changes of soil labile organic carbon and Carbon pool management index (CMPI) under different ecological restoration patterns can provide valuable information for evaluating the effects of ecological restoration measures on soil quality improvement, and screening optimized ecological restoration patterns on desertification forest and grassland. In this study, soil labile organic carbon fractions and CPMI were investigated by applying field investigations and laboratory analyses to desertification grassland receiving different patterns of ecological restoration in Zoige. Three main ecological restoration patterns were used to control desertification of grassland in Zoige, including shrub-grass intercrop pattern I (stripe Tamarix ramosissima incteropping herbs, such as Poa pratensis, Elymus nutan and Ajuga lupulina, SGI), shrub-grass intercrop pattern II (circular Tamarix ramosissima incteropping herbs, such as Poa pratensis, Cremanthodium reniforme, Cirsium japonicum, Daucus carota and Vicia sepium, SGII), and the sand-barrier plus shrub-grass intercrop pattern (the sand-barriers of Tamarix ramosissima plus Tamarix ramosissima incteropping herbs, such as Tamarix ramosissima, Poa pratensis, Elymus nutan, Ajuga lupulina, Daucus carota, SBSG).The results showed that the values of soil organic carbon and its labile fractions contents were higher in the three ecological restoration grasslands than in the desertification grassland without ecological restoration measures (DG). Compared to the DG, the contents of soil microbial biomass carbon (MBC), dissolved organic carbon(DOC), easily oxidized organic carbon(EOC), and particulate organic carbon(POC) in whole profile under the SGI pattern were increased by 36.6%, 139.0%, 89.4%, 130.9%, respectively, and those in the SGII pattern were increased by 2.7%, -43.9%,15.0%,49.7%, respectively, and those in the SBSG pattern were increased by 82.4%,21.8%,56.2%,170.3%, respectively. This indicated that the ecological restoration patterns of SGI and SBSG were similarly effective at improving soil organic carbon, and both were superior to the SGII pattern. The distributed proportions of soil active organic carbon between the three ecological restoration and desertification grassland were difference, for instance the distributed proportion of DOC presented a vertical fractionation in the SGI pattern. The values of CPMI under three ecological restoration patterns were exceeded 100%. This implied that soil quality can be improved by the three ecological restoration patterns, and the order of the improved level was SGI (CPMI, 182.5%) > SGII (CPMI, 157.1%) > SBSG (CPMI, 129.9%). The results suggest that soil easily oxidized organic carbon can be used as an optimized index to reflect changes of soil quality in different ecological restoration grasslands, and soil CPMI can be used to characterize the improved effectiveness of ecological restoration measures on soil quality.