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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (3): 132-139.doi: 10.11707/j.1001-7488.20150317

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Variation of Aboveground Biomass of Larix principis-rupprechtii Plantation along Slopes in the Diediegou Watershed of Liupan Mountains

Han Xinsheng1,2,3, Deng Lilan1, Wang Yanhui2, Xiong Wei2, Li Zhenhua2, Liu Qian2, Wang Yanbing2, Sun Hao2   

  1. 1. Forestry College of Southwest Forestry University Kunming 650224;
    2. Key Laboratory of Forestry Ecology and Environment of State Forestry Administration Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry Beijing 100091;
    3. Institute of Desertification Control, Ningxia Academy of Agriculture and Forestry Sciences Yinchuan 750002
  • Received:2013-12-28 Revised:2015-01-27 Published:2015-04-10

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Abstract:

【Objective】In general, forest biomass shows a notable variation with slope variables, such as slope direction and slope position, etc., especially in the arid or semi-arid regions where the precipitation is limited and the redistribution of soil water is remarkable. Up to now, it is hard to conveniently and accurately measure the biomass for the whole slope. In this study, the emphasis was placed on quantification of the variation of forest biomass along the slope and its spatial pattern. And considering the scale effect, a method of assessing forest biomass of a whole slope up-scaling from a certain plot was derived, providing technical support for improving forest management and implementing intensive tending. 【Methods】 Methods To achieve the objectives, two representative slopes (a half-shady slope and a shady slope) covered by 27-year-old Larix principis-rupprechtii plantation were chosen in the small watershed of Diediegou within the semi-arid region of Liupan Mountains, Northwest China. On each slope, six plots each with an area of 20 m×20 m were set up along the slope topdown. The aboveground biomass was measured in mid-July of 2012. In the analysis, the "horizontal distance from the slope top" was used as a variable to quantify the variation of the forest biomass along the slope, and also the relationship between the biomass of a certain plot and the average of the whole slope. 【Results】The average aboveground biomass was 52.36 t·hm-2 on the half-shady slope, 18.16% lower than that on the shady slope. The variation range was 42.50 t·hm-2 on the half-shady slope, 14.71% higher than that on the shady slope, indicating a stronger impact on half-shady slope than on the shady slope. On the other hand, the variation trend of aboveground biomass was similar on both slopes, i.e., the aboveground biomass increases gradually from top down, reaches the maximum at the lower part (half-shady slope) or middle-lower part (shady slope), and thereafter decreases till the slope foot. This is probably due to the redistribution of soil water on the slope. Along the increasing horizontal distance (x, m) from the slope top, the moving averages of aboveground biomass over the slope section (y, t·hm-2) increased gradually, with the relation of y=2×10-7x3－7×10-5x2+0.067 5x+30.838 (R2=0.995 7) for the half-shady slope, and y=－2×10-7 x3－8×10-5x2+0.121 9x+40.875 (R2= 0.999 8) for the shady slope. The moving average of aboveground biomass increased by 4.92 t·hm-2 for each 100 m of horizontal distance from the top on the shady slope, 21.66% less than the average of 6.28 t·hm-2 on the half-shady slope. This indicates that the spatial scale effect on the aboveground biomass exists on both slopes, however, it was weaker on the wetter shady slope than that on the half-shady slope. Furthermore, the ratios of aboveground biomass at a certain plot to the slope average (Y) varies nonlinearly along the relative distance of plots from slope top (X, m), which can be expressed as Y=－7×10-8X3 +4×10-5X2－2.2×10-3X+0.643 2 (R2=0.932 1) for the half-shady slope, and Y=－1×10-8X3+1×10-6X2+3×10-3X+0.620 4 (R2=0.973 9) for the shady slope. With these relations, the average of aboveground biomass for the whole slope can be up-scaled from plot at a certain slope position. 【Conclusion】In this semi-arid mountainous region, the variation of forest biomass along the slope positions follows a pattern of unimodal type, which is mainly due to the redistribution of soil water on the slope. And it is good to quantify the variation of forest biomass and its spatial scale effect by using the "horizontal distance from the slope top" as a spatial variable. Based on the work above, a convenient and accurate calculation of forest biomass of the whole slope was obtained.

Key words: Larix principis-rupprechtii, aboveground biomass, slope variation, scale effect, water condition, Liupan Mountains

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