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晋西黄土区油松林分结构与水土保持功能的多因子复合关系

Multifactor Relationships between Stand Structure and Soil and Water Conservation Function of Pinus tabulaeformis Plantations in the Loess Plateau of Western Shanxi

  • 摘要:
    目的 量化研究晋西黄土区的油松人工林林分结构与水土保持功能,揭示二者的多因子复合关系,为黄土高原植被建设提供借鉴。
    方法 选取蔡家川流域16块20 m×20 m林龄为28年的油松人工林标准样地,并划分成64块10 m×10 m样方,利用结构方程的方法构建地形-林分结构-水土保持功能的关系模型。其中将地形因子、水平结构、垂直结构、涵养水源和保育土壤、拦沙减沙作为潜变量,调查实验获取的各项指标作为观测变量。
    结果 油松林的水平结构是对涵养水源和保育土壤、拦沙减沙两类水土保持功能影响最为显著的潜变量,其路径系数分别为−0.93和0.79。而在其对应的观测变量中,林分密度和林木竞争指数是主导水平结构的因子,其路径系数分别为0.98和0.97,总影响系数分别为−0.987和−0.956,且较易调控。受结构因素影响较大的敏感功能因子为产流量、产沙量和林冠截留率,其路径系数分别为0.97、0.91和0.69,总影响系数分别为0.986、0.961和0.731。地形因子通过影响林分结构、在一定程度上影响水土保持功能。
    结论 提出黄土高原地区适宜的油松林分密度范围为1 100~1 400株·hm−2,据此来调整林分密度、林木竞争指数等结构指标,将对地区涵养水源、保育土壤和拦沙减沙起到良好效益,多因子协同调控将进一步提升黄土高原的植被质量,发挥植被的水土保持效能。

     

    Abstract:
    Objective To study quantitatively the multifactor relationships between the stand structure and soil and water conservation function of Pinus tabulaeformis plantation in the Loess Plateau of western Shanxi, so as to provide references for vegetation restoration in the Loess Plateau.
    Method Sixteen standard sample plots of 20 m×20 m, which were further divided into sixty-four 10 m×10 m quadrats, were established for a tree census in Caijiachuan watershed of the Loess Plateau, Shanxi Province, China. The age of these trees was about 18 years. Based on the observational and experimental data, a topography-structure-function model was built using a structural equation modeling (SEM) approach. The latent variables were the topographical factors, horizontal structure, vertical structure, soil and water conservation, and sediment reduction.
    Result The results indicated that the horizontal structure of the P. tabulaeformis stand was the most obvious latent variable, which was expressed in the path coefficients corresponding to soil and water conservation (pc=−0.93) and sediment reduction (pc=0.79), respectively; the stand density and tree competition index were the major drivers of the structure, with path coefficients of 0.98 and 0.97 and influence coefficients of −0.987 and −0.956. These factors were easily regulated. The sensitive functional factors that were greatly affected by structural factors were the runoff yield, sediment yield and canopy interception rate. The path coefficients were 0.97, 0.91 and 0.69, respectively and the total impact coefficients were 0.986, 0.961 and 0.731, respectively. Otherwise, the topographic factor affected soil and water conservation function through affecting the stand structure. should be kept stable within the range from 1 100 to 1 400 trees/hm2. Adjusting the stand density or tree competition index can effectively provide good benefits for soil and water conservation and sediment reduction. Multi-factor synergy can improve the vegetation quality and further promote the soil and water conservation efficiency in the ecologically significant loess area.

     

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