土壤微生物膜对风沙土固沙保水特性的影响

土壤微生物膜胞外聚合物具有较强的黏结性,为增强风沙土抗蚀性,提高风沙土保水性提供了新途径。鉴于此,该研究采用室内控制试验设置6个微生物菌剂施用水平(0、1、3、5、7和10 g/kg),以期阐明土壤微生物膜对风沙土特性的影响。研究结果表明:1)施用微生物菌剂可产生土壤微生物膜,并胶结风沙土颗粒。2)试验结束时(第49 d),与对照组相比,不同菌剂施用处理的土壤容重降低0.54%～8.88%,孔隙度提高0.39%～3.91%,含水率显著提高0.11%～0.25%(P0.05),大团聚体质量分数增加5.59%～25.01%,土壤pH值由7.16显著增加至8.32～9.23(P0.05)。3)土壤多糖含量对土壤特性的解释率为47%,是影响土壤特性的关键因素。土壤微生物膜能够有效改善风沙土特性,增强风沙土抗蚀性,提高风沙土保水性,但较高的微生物菌剂施用量会增加土壤pH值,造成土壤盐碱化,建议微生物菌剂施用水平为1～5 g/kg。研究成果有利于深入理解微生物膜固沙保水机制,并可为沙化土地防治新技术研发提供重要理论依据和科技支撑。

Effects of soil microbial films on sand fixation and water retention characteristics of aeolian soils

In natural environment, soil microorganisms usually exist in the form of microbial aggregates rather than the free single microbial cell by secreting extracellular polymeric substances on the surface of soil particles. These microbial aggregates are widely known as soil microbial films. Soil microbial films are an important adaptive approach for soil microbial self-protection and efficient growth. In addition, more and more people are realizing that soil microbial films potentially contribute to the anti-erodibility and water retention improvement of aeolian soils due to the strong cohesiveness of the extracellular polymeric substances. Therefore, as an emerging research approach, soil microbial films are at the forefront for desertification combating. However, due to the mechanism of this improved process remains unclear, these knowledge gaps have been hindering soil microbial films to be an alternative to the traditional techniques for desertification combating. In this study, the controlled experiment was conducted in a greenhouse using the common aeolian soils and soil bacteria (Bacillus subtilis and B. pumilus). 6 microbial agents (0, 1, 3, 5, 7 and 10 g/kg) were involved to test various soil properties and to identify the ecological function of soil microbial films. The results indicated that 1) Soil microbial films were successfully and largely induced by the microbial agents and clearly detected by the scanning electron microscope at multiple scales. In details, soil microbial cells first gathered, and then filled the space and cement aeolian soil particles using extracellular polymeric substances. In this process, soil microbial biomass carbon and nitrogen as well as soil polysaccharide were all increased, which were 2.41%-8.82%, 0.79%-8.60%, and 13.25%-55.13% higher than the control group, respectively. 2) On the 49th day of the experiment, most of the soil properties were increasing affected by soil microbial films as follow soil porosity (0.39% -3.91%), soil moisture (0.11%-0.25%, P<0.05), soil aggregates (5.59%-25.01%), and soil pH value (from 7.16 to 8.32-9.23, P<0.05). Soil bulk density was the only index which was in a deceasing tendency (0.54%-8.88%). 3) According to the redundancy analysis, soil polysaccharide was the most critical factor affecting aeolian soils with the highest interpretation rate (47%), followed by soil microbial biomass nitrogen and carbon. This was due to soil polysaccharide was main component of extracellular polymeric substances and played an important role in the formation of soil microbial films, backing up the ecological function of soil microbial films in soil improvement. In conclusion, soil microbial films effectively improve aeolian soils involving anti-erodibility and water retention. However, what is worth noting is that the microbial agents in a high concentration significantly increased soil pH resulting in soil salinization. Therefore, we highly recommended that the suitable microbial agents were 1-5 g/kg. Moreover, the recipe of adsorbent is also can be optimized to alleviate and curb soil salinization. This improved information is expected to provide a better understanding of the mechanism of soil microbial films affecting sand fixation and soil moisture, eventually and substantially contribute to a firm theoretical basis and scientific & technological support for the new technology exploration of desertification combating in a soil microbial approach.