关键词: 耕播方式, 根系发育, 稻茬小麦, 土壤水分, 土壤硝态氮含量

Abstract: We analyzed the community structure and floristic characteristics of Pinus tabuliformis forest in the South Lake Park in Changchun. Based on the first-order pattern test discriminant theory, the species composition and structure of P. tabuliformisforest were studied using diameter class as an age-level proxy indicator. The results showed that the trees belong to seven families, nine genera and 10 species. That means the tree composition was monotonous and unreasonable at species, genus, and family levels. The floristic element at the family level was mainly dominated by pan-tropical with certain proportions of cosmopolitan and north temperate elements. The north temperate was the dominant of genus. The abundance and importance value of P. tabuliformis in the communities were predominant, but its dominance in DBH and height was not obvious. There was a normal distribution in diameter class forP. tabuliformis. The communities were dominated by middle-aged trees, followed by near-mature and mature trees, with few seedlings and saplings. These communities were stable but with poor regeneration ability. The P. tabuliformis population in all the communities showed aggregated distribution, while a uniform distribution occurred on each single plant community. The types of population aggregation changed with different ages in spatial pattern discrimination. With the shrinking of the spatial scale, the distribution pattern of P. tabuliformis population changed from aggregated type to uniform type.

Key words: wheat after rice, root growth, soil nitrate-nitrogen content, tillage and sowing practice, soil moisture