关键词: 间作, 氮, 雍菜, 水稻, 竞争指数, 硅

Abstract: Pinus tabuliformis is a dominant species in the most widely distributed temperate coniferous forest community in northern China. The species is resistant to low temperature, dry conditions and poor soil nutrient status. It is also one of the most important tree species for forestation in large parts of northern China. In order to study the spatial distribution pattern of P. tabuliformis community, a 100 m ×100 m plot of natural P. tabuliformis stand was established in Qiliyu Forest Farm in July 2013. All trees in the plot were tagged, mapped and measured. The measurements included the diameter at breast height, total tree height and two crown diameters (eastwest and northsouth directions). The fractal properties of the spatial pattern of P. tabuliformis in the plot were studied by using the boxcounting dimension, information dimension and correlation dimension of fractal theory. The results showed that the high box-counting dimension (1.785) and correlation dimension (1.826) reflected a relatively high degree of individual spatial relatedness, sharp intraspecific competition and powerful spatial occupying of P. tabuliformis population. Information dimension of population pattern (0.262) and the scale variation degree of pattern intensities were low and the individuals were evenly distributed in space. Three fractal dimensions complement and influence each other. These results have important significance for more comprehensive and accurate interpretation of spatial pattern of P. tabuliformis population.

Key words: nitrogen, competition index, rice, intercropping, silicon, water spinach