Modelling of canopy structure and nitrogen use in plant communities

(1)研究了宫城川渡芒草地的冠层结构，结果表明，该草地的冠层结构中有蕨类植物、胡枝子属植物、菝葜属植物、过路黄属植物和野古草属植物13种，最低层有紫菀属植物、委陵菜属植物、苔草属植物、落新妇属植物、一枝黄花属植物和金丝桃属植物。各树种的总叶面积、光子吸收量与叶片氮素含量之间存在较强的相关性。上层植物叶面积大，平均光吸收量高，但单位地上生物量光吸收量不高。包括下层的物种具有高的SLA（每单位叶质量的叶面积），这导致它们高的生物量利用效率以吸收光子。(2)建立了一个光合作用模型来描述C3植物叶片的氮经济。根据光合作用蛋白的功能，将其分为五类。分析了氮素在各组中的投资对最大光合速率和光响应曲线的初始斜率的影响。适应性的变化。(3)阿索了叶龄、氮素营养和光量子通量密度对氮素在叶片间分配的影响。结果表明，随着氮素营养水平的降低，叶片氮素含量增加，叶龄的贡献也增加。

(1) Canopy structure with many species was studied in the Miscanthus sinensis grassland at Kawatabi, Miyagi Pref. There were 13 species with Pteridium, Lespedeza, Smilax, Lysimachia and Arundinella in the middle layrs, and Asterm Lactuca, Potentilla, Carex, Astilbe, Solidago and Hypericum in the lowest layrs. There were strong correlations between total leaf area, photon absorption and the amount of leaf nitrogen in each species. Species comprising the upper layrs had larger leaf area and highter photon absorption averaged over leaf area, but had not higher photon absorption per unit aboveground biomass. Species comprising the lower layrs had high SLA (leaf area per unit leaf mass), which led to their high efficiency of biomass use to absorb photons.(2) A model of photosynthesis was developed to describe the nitrogen economy of the leaf of C3 plants. Photosynthetic proteins were categorised into five groups according to their functions in photosynthesis. The effects of the investment of nitrogen in each of these groups on the maximal rate of photosynthesis and the initial slope of the light-response curve were analyzed. The changes in adaptive significance.(3) Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were aso as to avoid mutual shading of leaves. It was concluded that both leaf nitrogen and that the contribution of leaf age increases with the decrease in nitrogen nutrient level.