不同改良措施提高沙地初级生产力的机制:土壤微环境

Mechanism of different ameliorated methods to improve primary productivity of sand land: Soil microenvironment

土壤微环境恢复是实现沙地和沙化草地恢复的基础。然而,改良措施如何作用于土壤微环境从而提高沙地初级生产力的机制并不清楚。本研究在内蒙古锡林郭勒半固定沙地开展改良措施修复试验,设置对照、立体措施(结皮+保水剂)和综合措施(撒种+结皮+保水剂)处理,测定土壤物理性状(土壤容重、团聚体、温度和水分)和植物生物量,研究不同改良措施对沙地土壤微环境的影响。结果表明:立体措施和综合措施均改善了土壤结构(土壤容重降低、水稳性大团聚体增加),降低了水分蒸发,提高了土壤入渗,从而提高了土壤含水量;两种改良措施均降低了夏季日均温,这有利于减少水分蒸发,立体措施提高了早春日均温,可能会促进植物的萌发,从而提高雪水的利用率;两种改良措施均降低了温度日变化,白天较低的温度有利于降低水分的蒸发;综合措施较立体措施增加了撒种处理,提高了植物生物量,反过来又改善了土壤微环境,改良效果更佳。本研究揭示了立体措施和综合改良措施改善沙地土壤微环境,从而提高初级生产力的机制,为沙地和退化草原改良提供了理论支持,同时也具有重要的实践意义。

The restoration of soil microenvironment is the basis for the restoration of sand land and desertified grassland. However,it is not clear how the improvement measures interact with the soil microenvironment to increase primary productivity of sandy land. Here,we conducted an experiment in a semi-fixed dune in Xilingol,Inner Mongolia,to examine the impacts of different improvement measures on sandy soil microenvironment. We measured soil physical properties( soil bulk density,aggregates,temperature,moisture) and plant biomass under two treatments:three-dimensional measure( crust + water retention agent),comprehensive measure( seeding +crust + water retention agent) and control. Our results showed that both the three-dimensional and comprehensive measures improved soil structure( lower soil bulk density and higher water stability of large aggregates),increased soil infiltration and soil water content,but reduced water evaporation. Both ameliorations reduced the average daily temperature in summer,which was beneficial to reduce water evaporation. The three-dimensional measure increased the average daily temperature in early spring,which might promote seed germination,thus improving the utilization rate of snow water. Both measures reduced diurnal temperature variations. The lower daytime temperature was conducive to reducing water evaporation. Compared with the three-dimensional measure,the comprehensive measure increased plant biomass due to sowing treatment,which in turn improved soil microenvironment,and thus obtained a better improvement effect. This study provides empirical evidence for the use of three-dimensional and comprehensive measures for improving the microenvironment and primary productivity of sandy soils.