Tending methods for useful tree species invaded into unmanaged plantations and improving CO2 fixation capacity

为了结合卫星数据研究落叶阔叶林冠层光合生产，从叶片到林分水平研究了落叶阔叶林苗木和乔木叶片的光合特性。采用冠层塔法测定了7种落叶阔叶树的光合特性，结果表明，不同树种的光合特性存在一定的差异。白蜡树和枫木的净光合速率在夏季晴天中午最大值出现在树冠的第二层，而不是树冠的表层。冠的表面部分可以充当用于避免强光通量的遮蔽物。桤木和桦树叶片衰老始于树冠内部，而白蜡、枫木和枫木叶片衰老则始于树冠外部或顶部。叶绿素/氮比值随光通量密度的降低而增加。叶绿素含量与光合速率在同一种植物中呈明显的正相关关系，但在种间不存在相关关系。氮浓度与植物的光饱和光合作用呈显著正相关。落叶林隙或地面更新的苗木光合能力随季节变化剧烈。此外，在环境CO_2浓度下，光合速率的年际变化也很大。这种变化可能是由于叶片中的扩散阻力，因为它在饱和CO_2时消失了。落叶阔叶树的光合潜力可通过便携式氮素测定仪在野外进行测定，并可通过卫星图像监测叶片含氮量。

Photosynthetic characteristics of leaves of seedlings and trees of deciduous broadleaved forests were studied from a leaf to stand level to access canopy photosynthetic production in connection with satellite data. Photosynthetic traits of seven deciduous broad-leaved trees was detected with use of a canopy tower and showed specific pattern of each species. In ash and maple, maximum net photosynthetic rate at sunny midday in summer was detected at the second layr of a crown but not surface part of the crown. Surface part of a crown may act as shelter for avoiding strong light flux. Leaf senescence started from the inner part of the crown in alder and birch, but originated either in the outer or top portion of the canopy for ash, basswood and maple. Chlorophyll to nitrogen ratio in leaves increased with decreasing photon flux density, which was detected by portable machines. There is a clear positive correlation between chlorophyll content and photosynthetic rate in one species, however, not among species. Nitrogen concentration was positively correlated well with light saturated photosynthesis in a species. Photosynthetic capacity of tree seedlings regenerated in a gap or floor of forests with deciduous leaf habit changed drastically through the season. Moreover, year-to-year variation of the photosynthetic rate at ambient CO_2 concentration was markedly large. This variation may be due to the diffusion resistance in a leaf because it disappeared at saturated CO_2. Potential capacity of photosynthesis of deciduous broad-leaved trees can be estimated by a portable nitrogen detector in field, which may be monitored by satellite image by way of leaf nitrogen content.