三峡库区土地利用方式对土壤团聚体稳定性及有机碳分布的影响

Effects of Land Use Types on Soil Aggregate Stability and Organic Carbon Distribution in the Three Gorges Reservoir Area

    摘要
  • 摘要:
    目的 研究不同土地利用方式下土壤团聚体组成及有机碳分布特征，阐明三峡库区不同土地利用方式对土壤团聚体稳定性与土壤有机碳（SOC）固持的影响。
    方法 本研究以重庆市沙坪坝区虎溪镇西南部园地、菜地、青冈林地与竹林地为研究对象，采集0 ~ 60 cm土壤剖面样品，分析不同土地利用方式下土壤团聚体稳定性及SOC的垂直分布特征。
    结果 ①四种土地利用方式下，土壤机械稳定性团聚体均以大团聚体（2 ~ 5 mm）为主，水稳定性团聚体则以中团聚体（0.25 ~ 2 mm）和微团聚体（< 0.25 mm）为主。青冈林地团聚体稳定性整体较好，竹林地相对较差，且不同土地利用方式下团聚体稳定性随土层深度的变化规律存在显著差异。② SOC含量总体表现为园地（9.06 g kg−1） > 菜地（8.19 g kg−1） > 青冈林地（7.57 g kg−1） > 竹林地（7.18 g kg−1）。> 5 mm粒径团聚体有机碳含量在青冈林地和竹林地0 ~ 10 cm土层最高，到10 ~ 20 cm 土层发生显著下降。菜地0 ~ 20 cm土层2 ~ 5 mm粒级土壤团聚体有机碳含量最高，显著高于其他粒径团聚体有机碳含量。园地各粒径团聚体有机碳含量随深度变化无显著差异。0 ~ 10 cm土层，青冈林地的SOC储量（SOCR）最高（40.67 t hm−2），显著高于其他三种土地利用方式；而在10 ~ 20 cm土层，菜地的SOCR最高（21.80 t hm−2），其值较青冈林地和园地SOCR分别高出88.26%和82.73%。③ SOC和大团聚体含量是调控团聚体稳定性的主要因素，二者均与MWD呈显著正相关（P < 0.05）。
    结论 大团聚体是调控三峡区库不同土地利用方式SOC变化的关键，且在表层土壤（0 ~ 20 cm）中最为显著。深层土壤中（20 cm以下），与竹林、菜地相比，园地土壤大团聚体稳定性强，其固碳能力也较强。该结论为库区土地管理和土壤碳库精准调控提供了理论依据。

     

    Abstract:
    Objective The aims were to investigate the effects of different landuse types on soil aggregate structure and organic carbon distribution characteristics, in order to clarify the interaction mechanisms between soil aggregates and soil organic carbon (SOC) under various landuse patterns in the Three Gorges Reservoir Area.
    Methods The study was conducted in the southwest of Huxi Town, Shapingba District, Chongqing. Soil profile samples (0 - 60 cm) were collected from four landuse types: orchard, vegetable field, Cyclobalanopsis glauca woodland and bamboo forest. The stability of soil aggregates and the vertical distribution characteristics of SOC were analyzed.
    Results ① Under all four landuse types, mechanically stable aggregates were dominated by macro-aggregates (2 - 5 mm), while water-stable aggregates were primarily composed of medium (0.25 - 2 mm) and micro-aggregates (< 0.25 mm). The Cyclobalanopsis glauca woodland exhibited the highest aggregate stability, whereas the aggregate stability of bamboo forest was the lowest. Significant differences were observed in the variation patterns of aggregate stability with soil depth across the different landuse types. ② The SOC content in the landuse type followed the order: orchard (9.06 g kg−1) > vegetable field (8.19 g kg−1) > Cyclobalanopsis glauca woodland (7.57 g kg−1) > bamboo forest (7.18 g kg−1). In the Cyclobalanopsis glauca woodland and bamboo forest, the organic carbon content within the > 5 mm aggregate was the highest in the 0 - 10 cm, but decreased significantly in the 10 - 20 cm. In the vegetable field, the 2 - 5 mm aggregate contained the highest organic carbon content in the 0 - 20 cm, significantly exceeding those in other aggregate size classes. There was no significant difference across all aggregate sizes in each soil depth in the orchard. In the 0 - 10 cm, the SOC stock (SOCR) was the highest in the Cyclobalanopsis glauca woodland (40.67 t hm−2), significantly higher than that in the other three landuse types. In contrast, in the 10 - 20 cm, the vegetable field had the highest SOCR (21.80 t hm−2), exceeding that of the Cyclobalanopsis glauca woodland and orchard by 88.26% and 82.73%, respectively. ③ The SOC content and macro-aggregate content were the main factors controlling aggregate stability, and both showed significant positive correlations with MWD (P < 0.05).
    Conclusion Macro-aggregates play a key role in regulating SOC changes under different landuse types in the Three Gorges Reservoir area, with the most pronounced effects observed in surface soils (0 - 20 cm). In subsurface soils (below 20 cm), compared to bamboo forest and vegetable land, orchard soil exhibits stronger macro-aggregate stability and greater carbon sequestration capacity. These findings provide a theoretical basis for land management and precise regulation of the soil carbon pool in the reservoir area.

     

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