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Scientia Silvae Sinicae ›› 2023, Vol. 59 ›› Issue (4): 18-31.doi: 10.11707/j.1001-7488.LYKX20220621

• High-quality development of forestry in the Yellow River Basin • Previous Articles     Next Articles

Variation and Evaluation of Site Index of Black Locust Plantations on the Loess Plateau of Northwest China

Pingping Li1,2,Yanhui Wang2(),Wenbiao Duan1,*,Yirui Wang1,2,Pengtao Yu2,Li Zhen1,2,Zhixin Li3,Huijun Shang3,Zaijun Shi3,Yipeng Yu2   

  1. 1. College of Forestry, Northeast Forestry University Harbin 150040
    2. Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration Ecology and Nature Conservation Institute, Chinese Academy of Forestry Beijing 100091
    3. Guanshan Forest Farm, Jingchuan County, Pingliang City, Gansu Province Jingchuan 744306
  • Received:2022-09-08 Online:2023-04-25 Published:2023-07-05
  • Contact: Wenbiao Duan E-mail:wangyh@caf.ac.cn

Abstract:

Objective: The response of average height of dominant trees and site index (the average height of dominant trees with a baseline forest age of 15 years) of black locust (Robinia pseudoacacia) plantations to climatic and site factors was studied on the Loess Plateau, for establishing a model to evaluate site quality. Method: Based on the survey of sample plots and collected literature data, the single factor response law and appropriate form of response function of the average height of dominant trees were determined using the envelope method, and then a model was established by coupling multiple factors and calibrated with the measured data to evaluate the spatial difference in site index. Result: The impact of topography positions on the average height of dominant trees varied greatly, with a relative score of: gully bottom 1.000 > tableland 0.906 > lower part of ridge slope 0.837 > middle part of ridge slope 0.438 > gully slope 0.210 > upper part of ridge slope 0.176 > hilly top 0.000. Within the variation range of mean annual precipitation (MAP) below 550 mm, the average height of dominant trees increased with rising MAP rapidly, and thereafter gradually tended to level-off; the average height of dominant trees increased first and then decreased with rising mean annual air temperature (MAT) , with an optimal range of 7.5–11.0 ℃. The model of average height of dominant trees was established by coupling the effects of climatic and site factors, with a satisfactory fitness ( R2 = 0.72). According to the effects on the average height of dominant trees, both MAT and MAP on the Loess Plateau were divided into four levels (<6.0 ℃, too cold to grow; 6.0–7.5 ℃, cold and not suitable or relatively suitable for growth; 7.5–11.0 ℃, mild and the most suitable for growth; >11.0 ℃, warm and relatively suitable or not suitable for growth. <400 mm, too dry to grow; 400–450 mm, dry and not suitable for growth; 450–550 mm, moist and more suitable for growth; >550 mm, wet and the most suitable for growth). Then, the areas where black locust afforestation cannot be carried out on the Loess Plateau were determined, and the climate zoning of the rest areas where black locust afforestation can be carried out was proposed. The mild-wet, mild-moist, warm-wet and mild-dry subzones are suitable for black locust growth with an average site index of medium or higher classes (>7.5 m); while the cold-dry/moist and warm-moist subzones are not suitable for black locust growth as a whole. The site index of all site types in each subzone was calculated using fitted model for evaluating the site quality. Conclusion: The site index of black locust plantations on the Loess Plateau is affected by both climatic and site factors. The climatic zoning and site assessment with site index considering these effects can guide the refined site selection for afforestation and rational management of black locust plantations on the Loess Plateau.

Key words: black locust plantations, site index, coupling model, growth zoning, average height of dominant trees, Loess Plateau

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