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

结合卫星数据，从叶片到林分水平研究了落叶阔叶林幼苗和乔木叶片的光合特性。利用冠层塔对7种落叶阔叶树的光合特性进行了测定，得到了不同树种的光合特性特征。在夏季正午阳光充足时，白蜡树和枫树的净光合速率在树冠的第二层达到最大值，而在树冠的表层没有。冠的表面部分可以作为遮蔽物，以避免强烈的光通量。桤木和桦树的叶片衰老始于冠层内侧，而白蜡树、椴木和枫树的叶片衰老则起源于冠层的外侧或顶部。叶片叶绿素氮比随光子通量密度的减小而增大。叶绿素含量与光合速率在同一种内呈显著正相关，但在不同种间无显著正相关。氮浓度与光饱和光合作用具有良好的正相关关系。在落叶习性的林隙或地面上再生的树苗的光合能力随季节的变化而急剧变化。此外，在CO_2浓度下，光合速率的年际变化显著较大。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野外便携式氮素检测仪估算，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.