黄河三角洲盐碱地人工刺槐混交林细根分布研究

为研究黄河三角洲盐碱地人工刺槐混交林及纯林细根空间分布格局,选取绒毛白蜡刺槐混交林、臭椿刺槐混交林、刺槐纯林,采用土柱法取样,从细根生物量密度、表面积密度、体积密度、根长密度等方面研究盐碱地中不同林分中树木细根的垂直分布情况,从细根生物量分析不同林木细根垂直分布情况,研究不同人工林细根分布差异及土壤影响因子。结果表明:绒毛白蜡刺槐混交林在细根的生物量、表面积、体积、根长等方面都显著高于臭椿刺槐混交林和刺槐纯林;绒毛白蜡刺槐混交林95.77%细根生物量分布在0~60 cm土层,臭椿刺槐混交林85.37%细根生物量分布在0~40 cm土层,而刺槐纯林的细根在土壤中分布则比较均匀,0~40 cm土层细根占生物量总量的66.38%。绒毛白蜡细根生物量最高,显著高于其他林木。绒毛白蜡刺槐混交林细根表面积密度、体积密度、根长密度显著高于刺槐纯林;臭椿刺槐混交林高于刺槐纯林,差异不显著。绒毛白蜡刺槐混交林、臭椿刺槐混交林细根总根尖数分别是刺槐纯林的2.34倍、1.23倍,总分叉数分别为刺槐纯林的6.15倍、1.66倍。绒毛白蜡刺槐混交林、臭椿刺槐混交林、刺槐纯林树木细根生物量与土壤有效磷、速效钾含量呈显著正相关关系;绒毛白蜡刺槐混交林细根生物量碱解氮、有机质含量呈极显著正相关关系。适当的混交模式在一定程度上提高了人工林细根生物量,增强植物吸收土壤营养物质的能力,混交使人工林在盐碱立地条件下适应能力提高。

Fine root distribution in mixed Robinia pseudoacacia plantations in saline soils of the Yellow River Delta

To determine the distribution of fine roots of Robinia pseudoacacia mixed forests and pure forest in saline-alkali soils of the Yellow River Delta, fine root distributions in Fraxinus velutina and Robinia pseudoacacia mixed forest, Ailanthus altissima and Robinia pseudoacacia mixed forest and Robinia pseudoacacia pure forest were sampled with a soil column method. The vertical distributions of fine roots in different forest stands were analyzed for the distributions of fine root biomass density, fine root surface area density, volume density, root length density and other root parameters. The aim of the study was to clarify differences of roots distribution of different forests and their relationship with soil properties and to provide references for the vegetation recovery and tree species selection in saline soils of the Yellow River Delta. The results showed that fine root biomass, surface area, volume and root length of F. velutina and R. pseudoacacia mixed forest were significantly higher than those of A. altissima and R. pseudoacacia mixed forest and R. pseudoacacia plantation. About 95.77% of fine root biomass was distributed in the 0-60 cm soil layer for F. velutina and R. pseudoacacia mixed forest, 85.37% in the 0-40 cm soil layer for A. altissima and R. pseudoacacia mixed forest and 66.38% in the 0-40 cm soil layer for R. pseudoacacia pure forest. Although surface aggregation of fine roots was conducive to reducing the harmful effects of saline-alkaline conditions on the root, fine roots of R. pseudoacacia pure forest were more uniformly distributed in the soil. F. velutina and R. pseudoacacia mixed forest had the highest total fine root biomass (91.56 g in 2 500 cm² of soil), significantly higher than those of other trees stands. Fine root surface area, length and volume densities of F. velutina and R. pseudoacacia mixed forest were significantly higher than that of R. pseudoacacia pure forest. Fine root tips of F. velutina and R. pseudoacacia mixed forest and A. altissima and R. pseudoacacia mixed forest were respectively 2.34 and 1.23 times that of R. pseudoacacia pure forest. Root forks of F. velutina and R. pseudoacacia mixed forest and A. altissima and R. pseudoacacia mixed forest were respectively 6.15 and 1.66 times that of R. pseudoacacia pure forest. There was a significant positive correlation between stand fine root biomass with soil available phosphorus and soil available potassium contents. The correlation between fine root biomass with available nitrogen and organic matter content of F. velutina and R. pseudoacacia mixed forest was also very significant and positive. The research showed that some trees mixed patterns increased fine root biomass distribution and the ability of roots to absorb soil nutrient. This suggested that proper mixing patterns could increase the adaptability of tree plantations.