黄河三角洲滨海盐碱地11个造林树种细根解剖性状对土壤条件的响应

Abstract

细根作为植物与土壤连接的重要部位，能够反映植物对生存环境的适应性。以黄河三角洲滨海盐碱地不同立地条件下11个造林树种为对象，基于细根分支等级划分1-4级根序并进行解剖特征测定，分析细根解剖性状对滨海盐碱地不同土壤条件的响应规律。结果表明：（1）不同根序的细根直径存在显著差异，细根直径随根序升高呈增大趋势，而同根序的细根直径在不同树种间表现出显著的种间差异（P < 0.05）。1-2级细根皮层厚度、3-4级细根导管密度在树种间的差异均达显著水平（P < 0.05）。（2）在较为严重盐渍化土壤条件下（立地1），细根皮层厚度较其他立地显著增大，但细根导管密度较小；在轻度盐碱立地条件下（立地3），细根导管密度较大；较为严重的盐碱立地具有更为发达的细根直径及维管柱直径。（3）树种1-2级细根解剖结构与土壤环境关系最为密切，其中1级根直径与土壤pH值显著正相关（P < 0.05），与土壤硝态氮含量呈显著负相关（P < 0.05）。对土壤理化性质与细根解剖性状的冗余分析表明，前两个轴的特征值达0.640和0.196，土壤速效养分含量与轴一（RDA1）呈正相关，低级根解剖性状则与轴二（RDA2）呈显著负相关。低级根解剖结构以及土壤的pH值能解释较多树种的差异性，其中低级根直径与皮层厚度对盐碱环境表现出较强的响应。;As an important link between plant and soil environment, fine roots can reflect the adaptability of plants to the living environment. Based on the functional traits of fine roots, exploration on mechanism of plants adaptive to environment would be significant for the vegetation restoration. In this study, 11 tree species in different stand sites of coastal saline-alkali land were selected, and six anatomical traits of 1-4 order fine roots were examined, including the fine root diameter, root cortex thickness, root stele diameter, the number of vessels, vessel diameter, and vessel density. At the same time, the soil physical and chemical properties in the forestlands where the fine roots of tree species are sampled were determined. The responses of fine root anatomical traits to soil environments were analyzed, and the study would provide a scientific basis for the vegetation restoration and plant community construct on coastal saline-alkali lands. The result showed that The fine root diameters of different orders were significantly different, and the fine root diameters increased with the increase of root order, while the fine root diameters of the same root order showed significant interspecific difference (P < 0.05). The root cortex thickness in 1-2 order fine roots and the vessel density in 3-4 order fine roots also showed significant differences among tree species (P < 0.05). Based on clustering of forest lands, the roots had larger cortex thickness of 1-2 order roots but less vessel density of 3-4 order roots in site 1 (the relatively higher salinization of soil) than those of other two sites. Furthermore, the root diameters and the stele diameters were more developed in site 1 (the relatively higher salinization of soil). The anatomical structure of the lower order roots of tree species was most closely related to the soil environment. The diameter of the first order roots was positively correlated with soil pH (P < 0.05), negatively correlated with soil nitrate nitrogen (P < 0.05). The redundant analysis (RDA) of soil properties and fine root anatomical traits showed the characteristic values were 0.640 and 0.196 in the two axes (RDA1 and RDA2), and soil available nutrient contents were positively related to RDA1 while the anatomical traits of lower order roots were negatively related to RDA2. The anatomical traits and soil pH value could explain more information of the tree species differentiation in saline-alkali soil environments, and the root diameter and the root cortex thickness in lower order fine roots demonstrated strong responses to soil saline-alkali environments, which would provide some references for the selection of tree species for the vegetation restoration in coastal saline-alkali environment in the future.