晋西黄土区人工林细根与土壤水碳的耦合关系

以晋西黄土区山西离石典型人工林刺槐、侧柏、核桃为研究对象，研究其深剖面（0-500 cm）细根参数、土壤水分和有机碳的分布特征，并以农地为对照，评价各人工林土壤水分亏缺和有机碳积累效应，在此基础上探讨三者的耦合关系。结果表明：（1）3种人工林土壤浅层（0-70 cm）细根累计生物量占整个土层的56%-71%，具有明显表聚性。（2）3种人工林土壤深层（70-500 cm）土壤水分亏缺效应均显著高于浅层（P < 0.05），与农地相比，其亏缺值表现为：侧柏 > 核桃 > 刺槐。（3）3种人工林深层土壤有机碳密度占整个土层的77%-86%；与农地相比，侧柏和核桃土壤有机碳积累效应总体为正向积累作用，刺槐则相反。（4）在土壤浅层，细根参数与土壤水分和有机碳密度均有显著相关性，而在深层，细根主要与有机碳密度显著相关，与土壤水分的相关性仅在刺槐样地显著。晋西黄土区不同人工林深层细根分布有很大差异，且已对其深层土壤水分和有机碳的分布产生影响。综合来看，刺槐的细根分布已造成深层土壤水分亏缺，同时也不利于深层有机碳的积累。

Coupling fine roots with soil moisture and organic carbon in artificial forests in loess region of western Shanxi Province

In this study, the relationship between fine roots, soil moisture, and soil organic carbon in artificial forests was analyzed. Three tree species, Robinia pseudoacacia, Platycladus orientalis, and Juglans regia were selected in the loess region of western Shanxi Province, China. Soil and root samples were taken from 0-500 cm depths to analyze the distribution pattern of fine root parameters, soil moisture content (SMC), and soil organic carbon density (SOCD). Soil moisture deficit (SMD) and organic carbon accumulation (SOCA) in artificial forests were evaluated with long-term cropland as a control. The results showed that:(1) the cumulative proportion of fine root biomass in shallow soil layers (0-70 cm) ranged from 56% to 71%, which showed obvious surface aggregation in all three forests. (2) The SMD in deep soil layers (70-500 cm) was significantly higher than that in shallow soil layers of all forests (P < 0.05). Compared with the control, the SMD in deep soil layers of artificial forests ranked as P. orientalis > J. regia > R. pseudoacacia. (3) The SOCD in deep soil layers accounted for 77%-86% of total soil profile SOCD across different forests. Compared with the control, the SOCA in P. orientalis and J. regia plots was generally positive, while the SOCA in R. pseudoacacia plot was negative. (4) The fine root parameters were positively correlated with both SMC and SOCD in shallow soil layers. However, in deep soil layers, the positive correlation was observed mainly with SOCD. The significant correlation with SMC was found only in R. pseudoacacia plot. The deep distribution of fine roots considerably differed among three artificial forests in the loess region of western Shanxi, which had an obvious influence on the deep SMC and SOCD distribution. Overall, the fine root distribution of R. pseudoacacia contributed to SMD while negatively affecting SOCA in the deep soil.