金莲花产量抽样调查的样地最小面积与形状研究

A study on the plot minimum area and shape for sampling Trollius chinensis yield

抽样调查是植物资源调查的一种重要方法,样地的面积与形状是抽样调查的基础,影响着调查的效率与精度。为确定野生金莲花产量抽样调查的最适样地面积与形状,设计了边长或半径逐步增大的正方形、长方形、圆形3种样地,选择了Generalized Mitscherlich方程、Richard方程与Logistic方程拟合变异系数-面积的变化趋势。提出了以变异系数的变化率与调查费用最小为判据,确定样地最小面积的2种方法,并对不同形状的样地进行比较以确定适合的样地形状。结果表明,3种变异系数-面积曲线的拟合效果均较好,相关指数均达到0.94以上,但以Logistic方程最为稳定。以变化率确定的最小面积,同一样地形状表现为Richard方程>Logistic方程>General-ized Mitscherlich方程;采用同一个回归方程,样地最小面积表现为圆形>正方形>长方形,正方形与长方形较为接近。基于最小费用研究表明,同一样地形状采用不同回归方程所得最小费用相近,但最小面积各不相同;对于同一回归方程,样地最小面积同样表现为圆形>正方形>长方形,正方形与长方形相近的趋势。最后,综合确定正方形样地的最小样地面积为36 m2(6 m×6 m),长方形为32 m2(8 m×4 m),圆形为78.5 m2(半径5 m)。不同形状的样地,从所能达到的最小变异系数、相同面积与精度时的调查费用与不同回归模型反映的稳定性来说,长方形样地最好,正方形次之,但二者相差不大,圆形最差。

A sample survey is an important method for investigating plant resources.Plot area and shape underlie sampling surveys and influence survey efficiency and accuracy.To determine optimum plot area and shape for investigating yield of Trollius chinensis,three plot shapes（square,rectangle and circle） with a range of side lengths or radii were used to fit the CV（coefficient of variation）-area curve by the Generalized Mitscherlich equation,Richard equation and Logistic equation.Two methods were put forward for determining plot minimum area,one was based on CV change rate,the other on minimum investigating cost.The optimum plot shape was obtained by also comparing plot shape.The three CV-area models were all pretty good and the correlation coefficient was above 0.94,with Logistic equation the most stable.The minimum plot area estimated by change rate was in the order Richard equationLogistic equationGeneralized Mitscherlich equation for the same plot shape,and was circlesquarerectangle for the same regression equation： the areas of squares and rectangles were similar.The study also showed that the minimum investigation cost was close for the same plot shape and different regression models,but the minimum plot area varied.For the same regression equation,the minimum plot area based on minimum plot cost was circlesquarerectangle while the square and the rectangle were also similar.Finally and comprehensively,the minimum plot area of square,rectangle,and circle were determined as 36 m2（6 m×6 m）,32 m2（8 m×4 m）,78.5 m2（radius 5 m） respectively.The optimum plot shape was obtained from the minimum CV of plots of different shapes,cost of the same area plots and comparisons among regression models.The rectangular plot was the best followed by the square with little difference between them.The circle was the worst shape.