Shuitu Baochi Xuebao (Apr 2024)
Effects of Understory Vegetation on Soil Phosphorus Morphological and Availability in Larix gmelinii Forest in the Cold Temperate Zone
Abstract
[Objective] Due to the large differences in understorey vegetation and soil physicochemical properties of Larix gmelinii forest in the cold temperate zone of the Rreater Khingan Mountains, the characteristics and availability of soil phosphorus morphological changes of Larix gmelinii forest under different forests were studied, so as to provide scientific data for scientific evaluation of soil phosphorus supply level and phosphorus cycle in the cold temperate zone forest. [Methods] Four kinds of understory vegetation in the cold temperate zone of the Greater Khingan Mountains, namely, Larix gmelinii forest (Rhododendron simsii-Larix gmelinii forest, Rhododendron tomentosum-Larix gmelinii forest, Carex schmidtii-Larix gmelinii forest and Moss-Larix gmelinii forest) were selected as the research objects. Soil samples from the 0—5 cm, 5—10 cm and 10—20 cm soil layer were collected from June, August and October 2022. Hedley phosphorus classification method was used to determine the phosphorus content of different forms in soil. [Results] (1) During the observation period, soil active phosphorus (H2O—Pi, NaHCO3—Pi, NaHCO3—Po) and medium active phosphorus (NaOH—Pi, NaOH—Po) of the four understorey vegetation Larix gmelinii forest showed a decrease trend from June to October, and the content of medium active phosphorus accounted for 30.08% to 52.80% of total phosphorus.The content of inorganic phosphorus was higher than that of organic phosphorus. The content of active phosphorus and medium active phosphorus in 0—20 cm soil layer of Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest were higher than those of the Carex schmidtii-Larix gmelinii forest and Moss-Larix gmelinii forest. The soil stability phosphorus (HCl—Pi, HCl—Po, and residual—P) in the Carex schmidtii-Larix gmelinii forest was significantly higher than that in the other three larix forests, and the stable state phosphorus accounted for 58.86%～65.81% of the total phosphorus. (2) Soil total phosphorus (TP), available phosphorus (AP) and phosphorus activation coefficient (PAC) in Larix gmelinii forest were 391.81 to 1 081.02, 7.34 to 83.90 mg/kg, and 1.62% to 7.76% from June to October, respectively. The content of AP and PAC in the soil of the Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest were higher than those of the other two larix forests, showing higher phosphorus availability. On the other hand, there was insufficient phosphorus supply in the soil layer of the Carex schmidtii -Larix gmelinii forest and Moss-Larix gmelinii forest from 5—10 cm and 10—20 cm in August and October. (3) Soil moisture contentwas the main influencing factor of soil phosphorus in the Rhododendron simsii-Larix gmelinii forest and the Rhododendron tomentosum-Larix gmelinii forest, soluble carbon was the main influencing factor of the Carex schmidtii-Larix gmelinii forest, and ammonium nitrogen had a greater influence on the Moss-Larix gmelinii forest. [Conclusion] Understory vegetation had a significant effect on soil phosphorus morphological form and phosphorus availability in Larix gmelinii forest. The content of active phosphorus, medium active phosphorus and available phosphorus in the soil of Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest was higher, and the activation coefficients of P were all above 2.00%; However, the content of stable phosphorus in soil of the Carex schmidtii-Larix gmelinii forest was higher, and the availability of soil phosphorus was lower. This results are of great significance for the study of ecological function of understory vegetation and soil nutrient cycle in the cold temperate forest ecosystem.
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