兴安落叶松种群格局的分形特征:计盒维数

FRACTAL PROPERTIES OF THE SPATIAL PATTERN OF LARIX GMELINI POPULATION: BOX-COUNTING DIMENSION

分形维数是分形体填充空间程度的度量 ,种群格局计盒维数能够揭示出种群格局的空间占据程度及其尺度变化规律 ,拐点尺度指示出个体聚集尺度。本文应用计盒维数对大兴安岭主要森林类型中兴安落叶松种群空间格局进行的研究表明 ,兴安落叶松种群格局均具有统计自相似性。各类兴安落叶松林中兴安落叶松种群格局具有较高的计盒维数 ( >1 .5 ,接近 2 ) ,对空间占据程度较高 ,建群和优势地位明显 ,空间占据程度的强弱次序为越桔—兴安落叶松 ( 1 .82 9) >草类—兴安落叶松林 ( 1 .72 0 ) >杜鹃—兴安落叶松 ( 1 .70 5 )杜香—兴安落叶松林 ( 1 .5 1 3)。兴安落叶松—白桦林中 ,兴安落叶松处于劣势伴生地位 ,种群格局的计盒维数较低 ( 1 .371 ,远离2 ) ,空间占据程度低。通过对天然森林类型中兴安落叶松种群格局的计盒维数与兴安落叶松人工林的比较发现 ,兴安落叶松种群空间占据程度由高至低的次序为兴安落叶松人工林 ( 1 .86 8) >兴安落叶松天然林 ( 1 .6 92 ) >兴安落叶松—白桦林 ( 1 .371 ) ,揭示出兴安落叶松种群在不同森林类型中地位和作用的差异。

Box-counting dimension reflects the spatial occupation degree of an object. The box-counting dimension of population pattern discloses the spatial occupation degree of population and its scale variation degree, the inflection point indicates the aggregating scale of individuals. This study analyzed the scale variation degrees of the spatial patterns of Larix gmelini populations in several typical forest types in Daxingan mountains, China using box-counting dimension. The results showed that the spatial distributions of Larix gmelini populations were high(>1.5,near 2) in different types of Larix gmelini forests, which reflected the high spatial occupation degrees of the populations as the dominant species of these forest types. The order of spatial occupation degree was Vaccinium-Larix forest (1.829)>Grass-Larix forest (1.720)>Rhododendron-Larix forest (1.705)>Ledum-Larix forest (1.513). The Box-counting dimension of Larix gmelini population was lower (1.371, far from 2) in Larix-Betula mixed forest, which showed the low spatial occupation degree of the populations in accompaniment position in the forest. Comparisons on box-counting dimensions of Larix gmelini populations among natural forests and that of plantation showed that, the order of spatial occupation degree was Larix plantation (1.868)>Natural Larix forest (1.692)>Larix-Betula forest (1.371), which reflected the variation of functions and positions of Larix gmelini population in different forest types.