盐地碱蓬生长对滨海重盐碱地的改土效应

盐地碱蓬是滨海盐碱地生态系统群落演替中的先锋物种,也是植被建设的重要植物。为探究盐地碱蓬对滨海盐碱地的改土效应以及作用机制,通过滨海平原盐碱地原生盐地碱蓬群落土壤调查,结合室内土柱种植试验,研究了盐地碱蓬生长对滨海盐土土壤结构、土壤水分入渗特征及土壤盐分分布的影响,比较了盐地碱蓬通过植株吸收盐分和通过改善土壤结构促进盐分淋洗对滨海盐碱地降盐、改土的效果。结果表明:1)盐地碱蓬生长对滨海盐土土壤结构有明显的改善效果,野外生长盐地碱蓬的0～20cm土层土壤容重显著低于裸地,而土壤孔隙度显著高于裸地地块;室内土柱种植盐地碱蓬降低了各层土壤容重,平均降低6.16%;增加了各层土壤孔隙度,增加1.59%～5.15%。2)盐地碱蓬生长显著提升了滨海盐土土壤水分入渗性能。野外入渗试验结果显示,相同入渗时间内,生长盐地碱蓬的土壤累积入渗量、初始入渗率及稳定入渗率分别是裸地的3.6倍、2.5倍和3.0倍。室内土柱模拟试验结果显示,盐地碱蓬处理土壤的初始入渗率为0.08mm·min?1,是裸地处理的2.6倍;稳定入渗率为0.03mm·min?1,是裸地处理的3.0倍。3)盐地碱蓬的生长明显降低了土壤含盐量,盐地碱蓬收获后,野外调查试验和室内土柱试验中裸地处理0～40cm土层土壤含盐量分别降低2.67%和12.98%,而盐地碱蓬处理分别降低12.08%和49.28%。野外调查和室内土柱试验中,盐地碱蓬植株移走的盐量分别占总脱盐量的5.60%和2.26%,淋洗脱盐量分别占总脱盐量的94.40%和97.74%。以上结果表明,滨海重盐碱地种植盐地碱蓬具有明显的降低土壤含盐量的作用,这种作用除植株吸收带走部分盐分外,更重要的是通过盐地碱蓬的生长改善了土壤结构、加速了土壤水分入渗、促进了土壤盐分的淋洗。

Soil improving effect of Suaeda salsa on heavy coastal saline-alkaline land

Suaeda salsa is a pioneer species in community succession of coastal saline-alkali ecosystems, as well as an important plant for vegetation construction. In order to explore the soil improvement effect and mechanism of S. salsa on coastal saline-alkali land, the effects of S. salsa growth on soil structure, water infiltration and salt distribution were studied through soil investigation of a primary S. salsa community and indoor soil column planting experiment. Meanwhile, the effects of salt absorption by S. salsa and salt leaching by soil structure promoting were compared and evaluated. The results showed that:1) the growth of S. salsa had an obvious effect on improving the soil structure of coastal saline soil. In the field investigation, the soil bulk density in the 0-20 cm soil layer of S. salsa patch was significantly lower than that in the bare land patch, and the soil porosity was significantly higher than the bare land patch. In the soil column experiment, planting S. salsa reduced soil bulk density of each soil layer, with an average decrease of 6.16%, an increased soil porosity by 1.59%-5.15%. 2) The growth of S. salsa significantly promoted the soil water infiltration capability of coastal saline soil. Field infiltration test results showed that, in the same infiltration time, the cumulative infiltration, initial infiltration rate and stable infiltration rate of S. salsa patch were 3.6, 2.5 and 3.0 times of bare land patch, respectively. The results of soil column simulation tests showed that the initial infiltration rate of S. salsa treatment was 0.08 mm·min^-1, which was 2.6 times that of bare land treatment, and the stable infiltration rate was 0.03 mm·min^-1, which was 3 times that of bare land treatment. 3) The growth of S. salsa significantly reduced the soil salinity. After the harvest of S. salsa in the field investigation and soil column experiment, the soil salinity in the 0-40 cm soil layer in bare land treatment decreased by 2.67% and 12.98% respectively, while that of S. salsa treatment decreased by 12.08% and 49.28% respectively. In the field investigation and soil column experiment, 5.60% and 2.26% of the total desalination were due to harvesting S. salsa, however, leaching desalination accounted for 94.40% and 97.74% of total desalination, respectively. The above results show that planting S. salsa in coastal heavy saline-alkali land has an obvious effect on reducing soil salinity. Besides plant absorption, it also promoted soil salt leaching through improving soil structure and accelerating soil water infiltration.